| 1. |
- Abele, H., et al.
(författare)
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Particle physics at the European Spallation Source
- 2023
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Ingår i: Physics reports. - : Elsevier. - 0370-1573 .- 1873-6270. ; 1023, s. 1-84
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Forskningsöversikt (refereegranskat)abstract
- Presently under construction in Lund, Sweden, the European Spallation Source (ESS) will be the world’s brightest neutron source. As such, it has the potential for a particle physics program with a unique reach and which is complementary to that available at other facilities. This paper describes proposed particle physics activities for the ESS. These encompass the exploitation of both the neutrons and neutrinos produced at the ESS for high precision (sensitivity) measurements (searches).
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| 2. |
- Aguilar, J., et al.
(författare)
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Study of nonstandard interactions mediated by a scalar field at the ESSnuSB experiment
- 2024
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Ingår i: Physical Review D. - : American Physical Society. - 2470-0010 .- 2470-0029. ; 109:11
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Tidskriftsartikel (refereegranskat)abstract
- In this paper, we study scalar mediator induced nonstandard interactions (SNSIs) in the context of the ESSnuSB experiment. In particular, we study the capability of ESSnuSB to put bounds on the SNSI parameters and also study the impact of SNSIs in the measurement of the leptonic CP phase δCP. Existence of SNSIs modifies the neutrino mass matrix and this modification can be expressed in terms of three diagonal real parameters (ηee, ημμ, and ηττ) and three off-diagonal complex parameters (ηeμ, ηeτ, and ημτ). Our study shows that the upper bounds on the parameters ημμ and ηττ depend upon how Δm312 is minimized in the theory. However, this is not the case when one tries to measure the impact of SNSIs on δCP. Further, we show that the CP sensitivity of ESSnuSB can be completely lost for certain values of ηee and ημτ for which the appearance channel probability becomes independent of δCP.
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| 3. |
- Basarir, Hakan, et al.
(författare)
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Assessment of slope stability using fuzzy sets and systems
- 2013
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Ingår i: International Journal of Mining, Reclamation and Environment. - : Informa UK Limited. - 1748-0930 .- 1748-0949. ; 27:5, s. 312-328
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Tidskriftsartikel (refereegranskat)abstract
- To assess the stability of slopes, mining and geotechnical engineers frequently use empirical rock mass classification and characterisation systems. These methods are practical and often very useful in the preliminary design stage. Slope mass rating (SMR) system is one of the commonly used empirical methods to assess the stability of slopes. The SMR is obtained correcting basic rock mass rating (RMR) using four joint adjustment factors that consider the geomechanical relationship between the slope face and the joint affecting rock mass as well as the excavation method used. The factors included in the SMR system such as basic RMR, and correction factors involve some drawbacks such as uncertainties sourced from qualitative criteria, sharp class boundaries and fixed rating scales. These drawbacks are sourced from the complex nature of rock mass. To deal with these uncertainties, the fuzzy set theory is applied in this study to reliably determine basic RMR and adjustment factors. It was seen that fuzzy set theory can sufficiently cope with the common drawbacks in the determination of factors included in the SMR system.
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| 4. |
- Burgman, A., et al.
(författare)
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The ESSnuSB Design Study: Overview and Future Prospects
- 2023
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Ingår i: Universe. - : MDPI. - 2218-1997. ; 9:8
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Forskningsöversikt (refereegranskat)abstract
- ESSnuSB is a design study for an experiment to measure the CP violation in the leptonic sector at the second neutrino oscillation maximum using a neutrino beam driven by the uniquely powerful ESS linear accelerator. The reduced impact of systematic errors on sensitivity at the second maximum allows for a very precise measurement of the CP violating parameter. This review describes the fundamental advantages of measurement at the second maximum, the necessary upgrades to the ESS linac in order to produce a neutrino beam, the near and far detector complexes, and the expected physics reach of the proposed ESSnuSB experiment, concluding with the near future developments aimed at the project realization.
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| 5. |
- Burgman, A., et al.
(författare)
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The European Spallation Source neutrino super-beam conceptual design report
- 2022
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Ingår i: The European Physical Journal Special Topics. - : Springer Nature. - 1951-6355 .- 1951-6401. ; 231:21, s. 3779-3955
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Forskningsöversikt (refereegranskat)abstract
- A design study, named ESSνSB for European Spallation Source neutrino Super Beam, has been carried out during the years 2018–2022 of how the 5 MW proton linear accelerator of the European Spallation Source under construction in Lund, Sweden, can be used to produce the world’s most intense long-baseline neutrino beam. The high beam intensity will allow for measuring the neutrino oscillations near the second oscillation maximum at which the CP violation signal is close to three times higher than at the first maximum, where other experiments measure. This will enable CP violation discovery in the leptonic sector for a wider range of values of the CP violating phase δCPδCP and, in particular, a higher precision measurement of δCPδCP. The present Conceptual Design Report describes the results of the design study of the required upgrade of the ESS linac, of the accumulator ring used to compress the linac pulses from 2.86 ms to 1.2 μs, and of the target station, where the 5 MW proton beam is used to produce the intense neutrino beam. It also presents the design of the near detector, which is used to monitor the neutrino beam as well as to measure neutrino cross sections, and of the large underground far detector located 360 km from ESS, where the magnitude of the oscillation appearance of νe from νμ is measured. The physics performance of the ESSνSB research facility has been evaluated demonstrating that after 10 years of data-taking, leptonic CP violation can be detected with more than 5 standard deviation significance over 70% of the range of values that the CP violation phase angle δCPδCP can take and that δCPδCP can be measured with a standard error less than 8° irrespective of the measured value of δCPδCP. These results demonstrate the uniquely high physics performance of the proposed ESSνSBESSνSB research facility.
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| 6. |
- Elhami, Ehsan, et al.
(författare)
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2D modeling of the Kristineberg mine stope
- 2012
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Konferensbidrag (refereegranskat)abstract
- Mining operations at the Kristineberg Mine approaches depths of more than 1300 m. Severe ground conditions are consequently expected due to the combination of weak rock formations and relatively high in-situ stresses. The required support techniques, however, are not unique and depend on the ground deformation characteristics. On the other hand, the complex geology of the mining zone induces different types and magnitudes of failures. As a result, to improve the support performance, the possible ground conditions which may arise from varieties of geological parameters at the mine need to be characterized. Among different geological parameters at the mine, the location of the rock formations is seen to be an important factor, influencing the deformation behavior of the rock mass. The aim of this study is to increase the understanding of how the rock mass behavior changes due to the location of the rock formations. The study is performed through numerical modeling of an unsupported stope using FLAC2D; the required input data are determined based on the field observations and the corresponding literatures. Then, the modeled deformation behavior of the stope is studied through “Parameter Analysis”. The results, which show the sensitivity of the ground deformation to the location of the surrounding rock formations, can be used in future support design analysis.
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| 7. |
- Idris, Musa Adebayo, et al.
(författare)
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Comparison of different probabilistic methods for analyzing stability of underground rock excavations
- 2016
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Ingår i: Electronic Journal of Geotechnical Engineering. - : Mete Öner. - 1089-3032. ; 21:21, s. 6555-6585
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Tidskriftsartikel (refereegranskat)abstract
- Stability analyses of underground rock excavations are often performed using traditional deterministic methods. In deterministic methods the mean or characteristics values of the input parameters are used for the analyses. These method neglect the inherent variability of the rock mass properties in the analyses and the results could be misleading. Therefore, for a realistic stability analyses probabilistic methods, which consider the inherent variability of the rock mass properties, are considered appropriate. A number of probabilistic methods, each based on different theories and assumptions have been developed for the analysis of geotechnical problems. Geotechnical engineers must therefore choose appropriate probabilistic method to achieve a specific objective while taking into account simplicity, accuracy and time efficiency. In this study finite difference method was combined with five different probabilistic methods to analyze the stability of an underground rock excavation. The probabilistic methods considered were the Point Estimate Method (PEM), the Response Surface Method (RSM), the Artificial Neural Network (ANN), the Monte Carlos Simulation (MCS), and the Strength Classification Method (SCM). The results and the relative merits of the methods were compared. Also the general advantages of the probabilistic method over the deterministic method were discussed. Though the methods presented in this study are not exhaustive, the results of this study will assist in the choice of appropriate probabilistic methods for the analysis of underground rock excavations.
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| 8. |
- Idris, Musa Adebayo, et al.
(författare)
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Consideration of the rock mass property variability in numerical modelling of open stope stability
- 2012
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Ingår i: Föredrag vid Bergmekanikdag i Stockholm, 12 mars 2012. - Stockholm : Stiftelsen bergteknisk forskning - Befo. ; , s. 111-123
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- This paper presents a probabilistic approach for modelling complex rock masses wherethe intrinsic properties are highly variable. For this study a complex orebody in aCanadian mine is used. The mechanical properties of the host rock and the ore in thismine are found to be intrinsically variable with high contrast between their mechanicalproperties. It is apparent that the use of traditional deterministic methods to study thebehaviour of the open stopes is not appropriate for this mine. Hence, in this study aprobabilistic approach is adopted which allows the propagation of the variability of theinput parameters in the numerical modelling. Three different approaches were used toanalyze the stability of the open stopes based on the distribution of the different materialproperties of the rock mass. The results of the analysis using the three methods werecompared and the limitations and the potentials of each of the methods were discussed.The study provides insight into the significance of the rock mass property variability inthe numerical modelling of open stope stability and different ways that it could beincorporated into the modelling.
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| 9. |
- Idris, Musa Adebayo, et al.
(författare)
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Numerical analyses of the effects of rock Mass property variability on open stope stability
- 2011
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Ingår i: 45th US Rock Mechanics /Geomechanics Symposium. - San Francisco, CA, USA : ARMA, American Rock Mechanics Association.
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Konferensbidrag (refereegranskat)abstract
- The rock mass is intrinsically variable in its physical and mechanical properties which makes it complex. This complexity is evident from the spatial random distribution of the properties from any site characterization program. The precise values for these properties are never known in most cases hence most geotechnical mine designs are based on fixed or discrete values of rock mass properties for stability analysis. This traditional deterministic approach neither reflects the inherent variability nor the uncertainty in the rock mass properties. Therefore, it is desirable to utilize a probabilistic approach which provides a range of possible results based on the variability in the rock mass properties. Understanding the effect of this random distribution and variability of the properties on stope stability is essential for more realistic mine design. In this study, a series of numerical analyses using the explicit finite difference element code FLAC, have been conducted to study the effect of the random distribution and variability of rock mass properties on the stope stability. The rock mass in the FLAC model is represented by different material properties randomly distributed to each zone. In order to compare the results, fixed average values of the material properties were also used for the FLAC model in another simulation. The results clearly indicate that rock mass property variability does affect the stope stability and that a deterministic approach to stope stability analysis could lead to conservative results.
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| 10. |
- Idris, Musa Adebayo, et al.
(författare)
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Probabilistic analysis of open stope stability using numerical modelling
- 2011
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Ingår i: International Journal of Mining and Mineral Engineering. - 1754-890X .- 1754-8918. ; 3:3, s. 194-219
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Tidskriftsartikel (refereegranskat)abstract
- A probabilistic approach is presented for the analysis of open stopestability. The approach considers the inherent variability and uncertainty whichare typical of rock mass properties. In this study, a series of numerical analyseswere performed using FLAC to study the stability of open stopes while takinginto account the variability in the rock mass properties. The rock mass wasdivided into six strength classes: three classes for the host rock and threeclasses for the massive sulphide ore. Each class was randomly distributed to theelements in the FLAC model. The host rock-to-massive sulphide ore ratio isenvisaged to have a strong influence on the stope. To verify this, three casesof different ore percentages were considered and the results compared.The results, which were presented as Probability Density Functions (PDFs),indicate that the zones of low stiffness show high range of displacements andthat the increase in the percentage of the ore significantly affects the stability ofthe stopes.
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| 11. |
- Idris, Musa Adebayo, et al.
(författare)
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Stochastic assessment of pillar stability at Laisvall mine using Artificial Neural Network
- 2015
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Ingår i: Tunnelling and Underground Space Technology. - : Elsevier BV. - 0886-7798 .- 1878-4364. ; 49, s. 307-319
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Tidskriftsartikel (refereegranskat)abstract
- Stability analyses of any excavations within the rock mass require reliable geotechnical input parameters such as in situ stress field, rock mass strength and deformation modulus. These parameters are intrinsically uncertain and their precise values are never known, hence, their variability must be properly accounted for in the stability analyses. Traditional deterministic approaches do not quantitatively consider these uncertainties and variability in the input parameters. To incorporate these variability and uncertainties stochastic approaches are generally used. In this study, a stochastic assessment of pillar stability using Artificial Neural Network (ANN) is presented. The variability and uncertainty in the rock mass properties at the Laisvall mine were quantified and the probability density function of the deformation modulus of the rock mass was determined using probabilistic approach. The variability of the in situ stress was also considered. The random values of the deformation modulus and the horizontal in situ stresses were used as input parameters in the FLAC3D numerical simulations to determine the axial strain in the pillar. ANN model was developed to approximate an implicit relationship between the deformation modulus, horizontal in situ stresses and the axial strain occurring in pillar due to mining activities. The closed-form relationship generated from the trained ANN model, together with the maximum strain that the pillar can withstand was used to assess the stability of the pillar in terms of reliability index and probability of failure. The results from this study indicate that, the thickness of the overburden and pillar dimension have a substantial effect on the probability of failure and reliability index. Also shown is the significant influence of coefficient of variation (COV) of the random variables on the pillar stability. The approach presented in this study can be used to determine the optimal pillar dimensions based on the minimum acceptable risk of pillar failure
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| 12. |
- Jones, TH, et al.
(författare)
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Damage mapping and monitoring in sublevel caving crosscuts at the Malmberget mine
- 2022
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Ingår i: Caving 2022: Fifth International Conference on Block and Sublevel Caving Volume Two. - : Australian Centre for Geomechanics. ; , s. 1019-1030
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Konferensbidrag (refereegranskat)abstract
- The LKAB’s Malmberget mine in Sweden is one of the largest sublevel caving mines in the world, with an annual production rate averaging 18 million tons. This high rate of production at depth (>1,000 m) creates significant mining-induced stress redistribution on a global scale. At a production-level scale, this redistribution results in undesirable amounts of deformation in the entries and typically leads to general degradation in the footwall contact zones. This is exacerbated by highly varied geological and geotechnical characteristics of the lithology often found in the contact zone. To better understand the impact of mininginduced stress on production level entries, a study was conducted to measure stress changes and associated deformation over a two year period, as mining progressed in the vicinity of the instrumentation. Three-dimensional relative stress measurements using digital hollow inclusion stress cells and multiple-point borehole extensometer measurements were combined with convergence and floor heave measurements and regular damage mapping throughout the contact zone to better understand the evolution of damage in these areas. A site-specific Entry Condition Rating (ECR) system was developed to help geomechanics better track and understand the expected performance of the crosscut given the current state of mining. The result of the work is a better understanding of where and when damage is expected to occur, and the ability to properly time the installation of secondary support in a pre-emptive manner.
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| 13. |
- Jones, Tristan, et al.
(författare)
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Design methods for variable-stress, variable-geology environments
- 2022
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Rapport (refereegranskat)abstract
- Building and excavating in the underground environment naturally results in changes in the stresses. Induced stresses can concentrate in sensitive areas leading to rock falls and high deformation. As construction proceeds to deeper levels, or as multiple excavations are created in the same area stresses accumulate and can overcome the strength of the geology hosting the excavations.Specifically, problems can be encountered when excavating through geologies with highly varied properties. Stresses in these areas are concentrated not only under the effect of multiple different excavations, but by the natural capabilities of the different geologies to withstand and/or transmit that stress. It is a situation in which analytical and/or empirical methods are insufficient, and numerical methods can produce inaccurate or non-verifiable results. Improvements in modelling methodology are required to enable the numerical tool to be of greater help to design in these situations where it is potentially unsafe, and certainly inefficient, to design based solely on “what was done before”.To better design openings and support systems in these areas, it is necessary to better understand how excavation-induced stresses and geologically driven stress concentrations interact to create rock failure. This project addresses this problem by using a combination of data collection in a controlled environment, and numerical modelling of complex, multi-opening excavations in order develop a method for improving design and support systems.The research generated significant amount of data which can be used for further research and has already been assessed in the daily mine operations and planning.
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| 14. |
- Jones, TH, et al.
(författare)
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Empirical damage prediction in sublevel cave crosscuts at the Malmberget mine
- 2022
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Ingår i: Caving 2022: Fifth International Conference on Block and Sublevel Caving Volume Two. - : Australian Centre for Geomechanics. ; , s. 1007-1018
-
Konferensbidrag (refereegranskat)abstract
- Building on the empirical research completed in the footwall contact zone of LKAB’s Malmberget mine, a method has been developed for predicting damage in the crosscut entries of the mine layout. Threedimensional stress measurements combined with analyses of measured and observed damage in the crosscuts have allowed new interpretations of the crosscut performance. Stress analysis focused on the relative differential stresses measured in the area of interest. These stress changes were then linked directly to observed changes in the entry condition according to the Entry Condition Rating (ECR) system, a damage mapping system developed for the mine. A bilinear model was used to describe the entry condition rate of change such that the peak measured differential stress corresponds to increased degradation rates. These bilinear degradation rate trends are shown to be directly related to the geotechnical qualities of the rock using the Geologic Strength Index (GSI) of the monitored locations, irrespective of lithology. The final step was to develop an empirical model that allows prediction of a crosscut’s future ECR based on changes in the relative differential stress and the GSI of the crosscut. In combination with simple numerical modelling tools the model can be used to predict ahead of time when additional reinforcement will be necessary.
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| 15. |
- Malmgren, Lars, et al.
(författare)
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The excavation disturbed zone (EDZ) at Kiirunavaara mine, Sweden - by seismic measurements
- 2007
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Ingår i: Journal of Applied Geophysics. - : Elsevier BV. - 0926-9851 .- 1879-1859. ; 61:1, s. 1-15
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Tidskriftsartikel (refereegranskat)abstract
- The presence of an excavation disturbed zone (EDZ) around an excavation boundary can significantly affect the overall performance of the excavation and the general safety of men and equipment. Hence, it has been an important subject of research in various rock excavation projects. The EDZ is generally defined as the rock zone beyond the excavation boundary where the physical, mechanical and hydraulic properties of the rock have been significantly affected due to the excavation and redistribution of stresses. For LKAB's Kiirunavaara underground iron ore mine in Sweden, the understanding of the EDZ is essential for optimal design of rock support. With this main objective an EDZ investigation was conducted at the mine using seismic measurement techniques. Cross-hole seismics and spectral analyses of surfaces waves (SASW) were the main techniques used. Borehole Image Processing Systems (BIDS) complemented the seismic measurements. The results show that an EDZ with a thickness of 0.5-1.0 m existed behind the boundaries of the mining drifts being investigated. The magnitude of the Young's modulus of this zone was 50% to 90% of that of the undisturbed rock.
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| 16. |
- Mertuszka, P., et al.
(författare)
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Blasting delay pattern development in the light of rockburst prevention : Case study from polish copper mine
- 2019
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Ingår i: E3S Web of Conferences. - : EDP Sciences. - 2267-1242.
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Konferensbidrag (refereegranskat)abstract
- In order to reduce the risk of induced seismicity related to underground mining, a number of preventive actions are applied in the form of passive and active prevention methods. The former are mainly of an organisational nature and their effectiveness is usually considered in the long term, while the active methods are mostly based on the detonation of explosives and are aimed to release the seismic energy accumulated in the rock mass. In this paper, modifications of the firing pattern aimed to concentrate the paraseismic vibrations while maintaining the appropriate excavation of the mining face has been verified on the basis of underground tests. The evaluation was based on fragmentation analysis. The obtained results confirmed, that the blasting pattern modifications related to the reducing of the face firing time do not cause significant differences in terms of the appropriate excavation of the mining face.
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| 17. |
- Mertuszka, Piotr, et al.
(författare)
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The Effect of the Blasthole Diameter on the Detonation Velocity of Bulk Emulsion Explosive in the Conditions of Selected Mining Panel of the Rudna Mine
- 2019
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Ingår i: Archives of Mining Sciences. - : Polish Academy of Sciences. - 0860-7001 .- 1689-0469. ; 64:4, s. 725-737
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Tidskriftsartikel (refereegranskat)abstract
- The blasting technique is currently the basic excavation method in Polish underground copper mines. Applied explosives are usually described by parameters determined on the basis of specific standards, in which the manner and conditions of the tests performance were defined. One of the factors that is commonly used to assess the thermodynamic parameters of the explosives is the velocity of detonation. The measurements of the detonation velocity are carried out according to European Standard EN 13631-14:2003 based on a point-to-point method, which determines the average velocity of detonation over a specified distance. The disadvantage of this method is the lack of information on the detonation process along the explosive sample. The other method which provides detailed data on the propagation of the detonation wave within an explosive charge is a continuous method. It allows to analyse the VOD traces over the entire length of the charge. The examination certificates of a given explosive usually presents the average detonation velocities, but not the characteristics of their variations depending on the density or blasthole diameter. Therefore, the average VOD value is not sufficient to assess the efficiency of explosives. Analysis of the abovementioned problem shows, that the local conditions in which explosives are used differ significantly from those in which standard tests are performed. Thus, the actual detonation velocity may be different from that specified by the manufacturer. This article presents the results of VOD measurements of a bulk emulsion explosive depending on the diameter of the blastholes carried out in a selected mining panel of the Rudna copper mine, Poland. The aim of the study was to determine the optimal diameter of the blastholes in terms of detonation velocity. The research consisted of diameters which are currently used in the considered mine.
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| 18. |
- Nilsson, Mikael, et al.
(författare)
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Fracturing in the footwall at the Kiirunavaara mine, Sweden
- 2014
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Konferensbidrag (refereegranskat)abstract
- The Kiirunavaara mine is a large scale sub level caving (SLC) mine located near the city of Kiruna in northern Sweden. It is owned and operated by LKAB (Luossavaara-Kiirunavaara AB). The mine produces approximately 28 million tonnes of iron ore annually. Over the last 30 years the mine has experienced a slow but progressive fracturing and movement in the footwall rock mass induced by the SLC operations. The footwall contact which assumes a “slope-like” geometry is partially supported by the caved material from the hangingwall. However, since the late 1980s damage has been observed on the footwall crest as well as within the footwall. Progressive rock mass movement in the footwall is indicated by surface subsidence and visual observations underground. The extent of the damage has traditionally been estimated using empirical relations. Most of the current long term underground infrastructure within the footwall is located at a considerable distance from the ore contact. However, for new developments on deeper levels it is imperative to predict the future extent of the damage volume. Approximating the position of the damage boundary in the footwall at the current state of mining would assist in predicting the extent and characteristics of the damage volume as the mine deepens. LKAB and LTU (Lulea University of Technology) have therefore initiated a joint research project to study the long term stability of the footwall at the Kiirunavaara mine. This paper constitutes part of the work in this research.The paper describes a damage mapping campaign and subsequent analysis of the Kiirunavaara mine footwall to approximate the outer boundary of the damage. The footwall was systematically mapped on 6 levels between 320 and 800 m. The mapping results were then used to interpolate damage lines on the respective levels. The damage lines were used to construct a continuous damage surface between the studied levels. Existing records of damage mapping, monitoring and predictions were reviewed and compared to the results from the current campaign. The new results show that, the outer damage surface appears to remain stationary on the upper levels while new damage was observed on the deeper levels. At levels above 740 m the damage is judged to be mainly controlled by movements along natural discontinuities. At levels below 740 m the majority of the damage seems to be stress induced.
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| 19. |
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| 20. |
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| 21. |
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| 22. |
- Saiang, David, et al.
(författare)
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A parameter study of the damaged rock zone around shallow tunnels in brittle rock
- 2006
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Ingår i: Rock Mechanics in Underground Construction. - Singapore : World Scientific and Engineering Academy and Society. - 981270437X
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Konferensbidrag (refereegranskat)abstract
- As part of an ongoing study on the mechanical characteristics of the damaged rock zone (DRZ) around underground excavations and its influence on the overall performance of the excavation, a parameter study was carried out using the continuum method of numerical analysis. This assisted in identifying the sensitivity of the parameters tested, thereby laying the groundwork for further numerical investigation. The main parameters investigated include the extent of DRZ, the strength and stiffness of DRZ, and the depth of the excavation. The main quantity used to test the sensitivity of these parameters is the response of induced stresses around the excavation boundary resulting from the variation in these parameters. In the study presented in this paper, typical in-situ stress and rock mass conditions observed for shallow tunnelling projects in Sweden are used. The results clearly demonstrate the effect of DRZ on the excavation as well as the criticality of various parameter combinations. The strength of DRZ although sensitive, is the most complex to define and the tool used in this study to determine the empirical plastic strength components, namely cohesion and friction, is felt to be uncertain.
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| 23. |
- Saiang, David
(författare)
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Back Analysis of Narrow Vein Open Stope Stability and Verification Using Kinematic and Empirical Methods
- 2023
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Ingår i: Proceedings of the Rocscience International Conference (RIC 2023). - : Atlantis Press. - 9789464632583 ; , s. 13-22
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Konferensbidrag (refereegranskat)abstract
- High walls of open stopes in underground stoping mines can be considered to behave in a similar manner to open pit slopes if stability is largely controlled by geological structures. With this assumption the kinematic method of analyses can be used to assess the stability of the footwall, hangingwall, the roof and floor of an open stope. This paper demonstrates the application of kinematic analyses tools such as Rocscience’s DIPS® and UNWEDGE® to assess the stability of underground stopes in a narrow vein mine. A back analysis was conducted, using both kinematic methods and the empirical stability graph method, after field investigation of stope failures and review of stope closure reports. The stability graph method showed that the designed stopes were stable with support. However, majority of the stopes audited have apparently failed or were in state of failure, i.e., unstable. Kinematic analyses showed that these stopes were certainly at risk of failure which confirmed the observations. The stability chart used by the mine was eventually adjusted based on the kinematic analyses and observations made, resulting in the stability graph having only three regions: stable, unstable and fail.
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| 24. |
- Saiang, David
(författare)
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Behaviour of blast-induced damaged zone around underground excavations in hard rock mass
- 2008
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The presence of blast-induced damaged zone around an excavation boundary has been an important concern in rock construction. It is generally believed that the presence of this zone can pose problems related to stability and flow and consequently impair the performance and functionality of the excavation. In fact, the immediate consequences of this zone are usually conceived in terms of safety and cost. Hence, some organizations have put in place guidelines for controlling the amount of damage induced by blasting. Since shotcrete or sprayed concrete is a widely used surface rock support, its performance depends primarily on the competence of the damaged zone. However, in some instances the use of shotcrete may unnecessary, but the lack of knowledge of the competency of the damage zone means, it is better not to take chances. It is therefore necessary to increase the knowledge and the understanding of the competency and behaviour of the damaged zone in order to predict the performance and functionality of a rock tunnel. To gain an understanding of the damaged or disturbed zone in general, significant efforts have been made over the last few decades in a broader area; the excavation disturbed zone. These efforts mainly focused on the characterization and classification of the damaged zone. Quantification of this zone has also been done in terms of mechanical, hydraulic and physical parameters, particularly to delineate the extent of the damaged zone. The characterization, classification and quantification of damaged zone were purpose specific and therefore, the definitions for damage zone are different and varying. In this thesis the damaged zone is defined as the zone where the rock has been significantly damaged such that the mechanical properties have been affected and that these changes are measurable by any state of the art measurement techniques. This definition also applies to the blast-induced damage zone. To be able to assess the significance of the blast-induced damage zone and its influence on the performance of an excavation, the mechanical behaviour of this zone must be understood. This thesis is therefore aimed in that direction and thus the objective. Several issues were investigated including; effects and consequences of blast-induced damage zone, most likely failure mechanisms, mechanical parameter sensitivity and their impact on the behaviour of the damaged zone, numerical modelling approach for damaged zone and indicators for failure from a continuum model, etc. A literature review and industrial questionnaire gave the direction for the investigations. Field and numerical methods were employed in the investigations. The results of these investigations are published in a series of papers that make up the thesis. In brief, the main results and conclusions can be summarized as follows: The blast-induced damage zone has been largely defined in terms of its extent and lacks a definition based on its inherent competency parameters, which are directly related to the stability of an excavation. The blast-induced damage zone thickness varies in most practical cases between 0.1 and 1.0 m, with an average ranging from 0.3 m to 0.5 m depending on whether perimeter blasting techniques are used or not. The reduction in the Young's modulus varies anywhere between 10 to 90 % of the undamaged rock value. In a field investigation reported in this thesis the Young's modulus of the damaged rock was found to vary between 50 and 90 % of the value for he undamaged rock mass. The thickness of the damaged zone was between 0.5 and 1.0 m. From the numerical study, the presence of the blast-induced damaged zone did affect the behaviour of the stability quantities, namely; deformation and induced boundary stresses. However, it cannot be concluded if the effects are significant enough to cause problems around an underground excavation in the hard rock mass type studied. The inherent properties of the damaged zone that affected its behaviour, identified in order of their significance are; the deformation modulus, followed by tensile strength and compressive strength. External factors such as the state of the in-situ stresses are seen to significantly influence the behaviour of the damaged zone. With the rock mass type and the in-situ stress regimes used in this thesis, the main failure mechanism within the damaged zone at shallow excavations is tension, while in deep excavations it is compression, as evaluated from the numerical analyses. The influence of the blast-induced damaged zone on failure is evident in shallow excavations but not in deep excavations. This was observed from the coupled continuum-discontinuum models. The study on the shotcrete-rock interface showed that the bond strength of the interface is important for the shear strength. Average bond strength of 0. 5 MPa was determined for interfaces with surfaces roughness with JRC values of 1-3, and 1.4 MPa for those with JRC values of 9-13. These values were determined for low normal load conditions ( MPa) which is often the case when shotcrete is used with rock bolt for rock support. The average adhesion or tensile strength of the interface was determined to be 0.56 MPa.
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| 25. |
- Saiang, David
(författare)
-
Blast-induced damage : a summary of SveBeFo investigations
- 2008
-
Rapport (övrigt vetenskapligt/konstnärligt)abstract
- This report presents a summary of the blast damage investigation carried out by SveBeFo (Swedish Rock Engineering Research) during the period 1991 to 2003 at various hard rock sites in Sweden. The objective of this report is to present a synopsis of the important factors that influence the development and extent of the blast-induced damage zone, nature and characteristics of blast-induced fractures, and a summary of the blast-damage thickness with reference to the existing perimeter blasting damage guidelines for tunnelling and drifting practices in Sweden. Ultimately this report will assist the author in developing numerical models to study the effects of blast-induced damaged zone on stability parameters. It has to be stated clearly that this report is intended as summary and not a reproduction of the works of SveBeFo. It may not also represent the actual conclusions or views of SveBeFo in areas where this author attempted to interpret and conclude from some of the data. Interested readers are strongly urged to consult the SveBeFo publications referenced in this report.The SveBeFo blast damage investigations during the period 1991 to 2003 were carried out at three principle hard rock sites: (i) Vånga granite quarry, (ii) LKAB's Malmberget and Kiruna mines and (iii) SKB's TASQ tunnel. The primary goal of these studies was to improve perimeter blasting guidelines for tunnelling and drifting in hard rock masses in Sweden. Within this scope were several objectives such as: (i) to develop guidelines for blast-induced damage control for drifting and tunnelling in hard rock masses, (ii) devise method for blast damage assessment, (iii) verification of the devised methods in tunnelling and drifting sites. Generally used perimeter blasting techniques, particularly smooth blasting, were employed in the tests. Multiple holes of different, but commonly used, diameters for perimeter holes were used. The explosives used were those commonly used for tunnelling and drifting. After the blasts saw cuts were extracted from the remaining rock, cut into manageable sizes, sprayed with penetrants (to make the blast-induced cracks traceable or visible) and crack parameters (length, quantity and pattern) investigated. The size and pattern of blast-induced damage were observed to depend on various parameters, namely; explosive parameters (explosive type, charge length, initiation method and coupling), blast hole pattern (burden, spacing and hole diameter), in-situ rock mass parameters (geology, in-situ stress, and rock strength and stiffness) and water in the holes. The thickness of the observed damage ranged between 0.1 and 1.2 m. An average damage thickness of 0.5 m was observed in the Kiruna and Malmberget mine drifts and 0.3 m in SKB's ÄSPE/TASQ tunnel and Vånga granite quarry.
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| 26. |
- Saiang, David, et al.
(författare)
-
Blast-induced damaged around tunnels – effects, concerns and numerical assessment : [Sprängskador vid tunneldrivning - effekter med avseende på deformationer och stabilitet]
- 2008
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Ingår i: Bergmekanikdag. ; , s. 41-50
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- Blast-induced damage is an important concern to construction of underground excavations. These concerns relate mainly to the after-blast effects on stability, water inflow, safety and costs. Such concerns have led to introduction of guidelines to regulate the extent of tolerable damage due to blasting. However, a true definition for blast-induced damage still remains vague, since the parameters used in measuring damage seldom relate to the stability parameters of the damaged rock. To assist in the better understanding of the effects of blast-induced damage a survey was conducted by the authors in late 2005 to obtain the views of practitioners (clients and contractors) involved in underground rock excavations. This paper presents firstly, a condensed summary of the responses from the survey. Secondly, results from the numerical assessment of the effects of the blast-induced damaged rock with respect to deformation and stability parameters are presented. Inputs based on typical Swedish rock mass conditions were used in the modelling, while the modelling assumptions were based on blast-induced damage observations from SveBeFo field study reports.
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| 27. |
- Saiang, David
(författare)
-
Blast-induced damaged zone studies : Final Report to Trafikverket
- 2011
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- This report is a summary and conclusions from the study on Blast-Induced Damage around underground excavations in hard rock, which was carried out as a PhD research project by the author. The project was funded by Vägverket and the research was conducted at the Division of Mining and Geotechnical Engineering at Luleå University of Technology. The work resulted in several publications; a PhD thesis, journal articles, conference articles and technical reports. The publications can be downloaded from: http://www.ltu.se/staff/d/davsai?l=en. This final report is compilation of the important elements from these various publications.Because the Blast-Induced Damaged Zone (BIDZ) is generally perceived to have a negative impact on the economics and performance of a tunnel many studies have been conducted to delineate the extent of the BIDZ. The primary goal has been to device ways to control or minimise the extent of this zone. As a result guidelines have been developed by concerned authorities, such as for example AnläggningAMA-98 (1999), to control the extent of BIDZ during tunnel construction. These guidelines however do not give recommendations about the strength and stiffness properties of the BIDZ, which are the most important parameters that control its behaviour and ultimately influence the stability and performance of tunnel.The extent of the BIDZ in majority of the practical cases varied between 0.1 and 1.0 m, with an average ranging from 0.3 m to 0.5 m. The stiffness magnitudes of this zone were as low as 10% to as high as 90% of that of the undamaged rock mass. Field investigation at Kiirunavaara underground mine (Malmgren et al, 2007) showed the stiffness of the BIDZ to vary between 50 and 90% of that of the undamaged rock mass, while the thickness ranged from 0.5 to 1.0 m. Although it was possible to deduce the modulus of the BIDZ the strength however, is the most difficult to measure or estimate. The most generic way to estimate the strength of the BIDZ is the use of a rock mass classification system in conjunction with a strength criteria, which was the approach used in the research by this author.Numerical studies of the BIDZ by this author showed that, the presence of this zone does affect the overall response of the near-field rock mass. This therefore implies the need for consideration of this zone during the tunnel design stage. The strength and stiffness of this zone were also found to affect the type of failure around the tunnel and its extent. However, it not is possible to state by what degree the BIDZ will affect the performance of a tunnel as it is relative. It is therefore wise to use guidelines to minimise damage even though it may be costly and unnecessary. In any case it would be beneficial to consider the sensitivity of an excavation, both subjectively and objectively, before emphasising the seriousness to stick to the blast damage guidelines.
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| 28. |
- Saiang, David, et al.
(författare)
-
Block Erosion of Unlined Rock Spillway Canals
- 2022
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- Canals and tunnels in hydropower plants must be able to receive high shock-like flows without damaging either the dam or the rock foundation. Although the canals often consist of rock, erosion can occur when water is released. The natural riverbeds and lakes in Sweden usually run along large faults and other zones of weakness in the rock. This is because the water could more easily erode its way along these weakness zones. Spillways of hydropower dams are generally unlined thereby exposing the bedrock to erosion during floods.This study focuses on block erosion mechanisms and characteristics in unlined spillway canals that comprises hard rock mass systems. Two hydropower dam spillway canals were investigated as case studies; identified as Dam1 and Dam 2. The spillway canals of these two dams have uniquely different bed rock characteristics. At Dam 1 the rock mass is very blocky with visually estimated GSI classification in the range of 50 to 70, while Dam 2 is composed of massive rock mass with visually assessed GSI classification of 70 to 90.The erosion characteristics observed in these two spillway canals are uniquely different. The rock mass is obviously the principal factor contributing to these observations. However, there are also other factors, namely the hydraulic factors, as well as the geometrical factors of the canals. In this report these factors have been described in detail. Three main mechanisms of block erosion were observed, (i) removal or plucking of rock blocks, (ii) fracturing of intact rock blocks and (iii) abrasion. At Dam 1 spillway canal all three mechanisms were observed to be significantly evident. At Dam 2, abrasion is the dominant mechanism of erosion. Hydraulic parameters, water pressure and velocity, affect the criticality of the erosion.Numerical simulations of the spillway canals were conducted using 3DEC. These simulations show that block displacements greater than 10 m are experienced within 1 to 2 minutes of flow. This observation is consistent with observations made during an actual discharge from a dam. Numerical simulations indicated that blocks with sizes less than 1 m3 would easily be plucked and transported downstream. If they are intact and with unfavourable geometry, they can be easily fractured by the spill water loads. Field investigations support these observations.Remedial measures would first require classification of a spillway canal into erosion domains based on erosion vulnerability. For example, the upstream sections of the channels are typically vulnerable to high intensity erosion. Hydraulic jumps, plunge pools, stilling basins, etc, have been typically used to break up the energy before the water flows downstream. However, erosion still occurs further down since the energy is still very large. Reinforcing the bedrock with artificial supports such as rock bolting, widening and levelling of canals, diverting the flow to less vulnerable areas of the canal, etc, have been some means to reduce block erosion. This study concludes that, remedial measures must start with identifying the mechanisms of block erosion, three of which have been described above. Domaining of the channels into erosion critically domains may also assist in monitoring and application of remedial measures. Empirical methods, such as Pells (2016) can be applied in each domain to identify their erosion potential. This study also concludes that the hydraulic pressure and displacements that occur around a rock block needs to be further investigated, either by field measurements in a spillway or by using physical models. In this way, it will be possible to better understand the conditions around blocks in a spillway and erosion mechanisms during a discharge.
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| 29. |
- Saiang, David
(författare)
-
Damaged rock zone around excavation boundaries and its interaction with shotcrete
- 2004
-
Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- When an excavation is carried out in a body of rock, the mechanical, hydraulic and physical properties of the rock surrounding the excavation will be disturbed. The zone in which these occur is called the Excavation Disturbed Zone (EDZ) and must be represented in the quantitative assessment of the near-field host rock. Therefore, numerous investigations of the EDZ have been conducted worldwide and are reported in for example, the International EDZ Workshops of 1996 and 2003. By definition EDZ encompasses both, the zone where the rock is physical damaged (mechanical properties are permanently affected) and the zone where the rock is only disturbed (mechanical properties not significantly affected). The former, i.e. the damaged zone, will impact significantly the overall performance of an excavation since the mechanical properties of this zone are considerably reduced. This zone is referred to as the Damaged Rock Zone (DRZ) and is the focus of this study. The strength and stiffness of this zone are important governing parameters that determine how this zone behaves, as well as how it zone interacts with shotcrete as surface rock support. Despite the fact that much has been covered on the subject of excavation damaged zone, most of these work were mainly focused on, (1) identifying factors that influence the development and extent of the damage zone, and (2) quantitatively measure the extent of the damaged zone. The main goal of these studies was for the reduction of this zone. Since, it has never been possible to completely eliminate this zone what is left is in fact to quantify this zone it terms of its strength and stiffness, in order to visualize how the excavation will perform with the presence of DRZ, including its interaction with the rock support systems, which will ultimately lead to recommendations for support optimization. In this regard only few researchers have gone a step further, from just delineating the damaged zone, to quantitatively estimate the stiffness of this zone. Although it is also desirable to measure the strength of the DRZ, it is at this point in time practically difficult and not to mention the complex physics involved. This thesis, as well as the future research, will focus on the behavior of the DRZ and its interaction with surface rock support. Questions about how the strength and stiffness vary with respect to their position and magnitude around the excavation will also be investigated with the help of numerical methods. In the study reported herein however, the primary focus is on, 1) the literature review aspect and 2) stage one field and experimental work on the DRZ and its interaction with shotcrete.
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| 30. |
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| 31. |
- Saiang, David
(författare)
-
Damaged rock zone study : a progress report
- 2008
-
Rapport (övrigt vetenskapligt/konstnärligt)abstract
- The subject of the damaged rock zone around an underground excavation is very complex. Much of these complexities relate to the physics of the rock properties and the highly anisotropic conditions of the EDZ. In rock physics, for example, the sough after rock properties such as Young's modulus (E) and the strength parameters (óc, c, ö, etc) are tensor quantities - that is they have spatial characteristics (3-dimensional). So the question usually is: Is it sufficient to relate these parameters (which are tensors) to vector quantities such as velocity (which is one- dimensional)? Obviously, there is no mathematical relationship for this. The anisotropy within the EDZ also complicates any process that attempts to estimate the magnitude of these properties. A drill and blast excavation will result in complex fracture patterns (irregularly shaped, cracks ranging from micro to macro sizes, rock bridges, etc). All these complexities will affect the kinematics of rock deformation and strength characteristics. A large volume of publications is available on investigations into the excavation disturbed zone. However, much of these investigations have focussed on identifying the factors affecting the development and extent of this zone, with the primary goal of minimising or if possible to completely eliminate this zone, which though is not possible. A questionnaire on EDZ was send to various organisations and individuals. The responses revealed various views on the EDZ. The mining industry for example, sees the EDZ from two sides of the coin: (i) it can act as protective blanket (destressed zone) by pushing high stresses further into the rock and in doing so protect the excavation, (ii) it can also jeopardise the safety of personnel and equipment as well as resulting in increased support costs. For nuclear waste isolation group the EDZ will provide a flow path for nuclear radiation to reach the atmosphere. Further still, for the civil engineering, the problem is largely related to stability, and maintenance and operational costs. Each of these cases is unique since the requirements are different. Which parameters are important and which factors need attention will depend on the nature and purpose of the excavation.
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| 32. |
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| 33. |
- Saiang, David
(författare)
-
Determination of specific rock mass failure envelope via PFC and its subsequent application using FLAC
- 2008
-
Ingår i: Continuum and distinct element numerical modeling in geo-engineering 2008. - : Itasca.
-
Konferensbidrag (refereegranskat)abstract
- While pursuing a numerical study on the behavior of the rockmass near a tunnel boundary at shallow depths, by continuum methods, it was realized that the yield mechanisms were not accurately captured using the input parameters obtained directly through the Hoek-Brown-GSI empirical system. It was evident that unless these mechanisms were accurately captured the behavior of the near-field rockmass cannot be correctly simulated. A question was then raised if PFC could be used to obtain a simple failure envelope/model for the rockmass in question and then use this model in the FLAC simulations - thus the object of this paper. The paper is presented in two parts as; (i) "numerical laboratory tests" involving biaxial compression and Brazilian tests on "synthetic rockmass samples" to determine the failure model and (ii) the subsequent application of the model in FLAC. The results are then presented and discussed, with the main conclusion that PFC can be used to determine the values of the input parameters for a continuum model.
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| 34. |
- Saiang, David, et al.
(författare)
-
Failure mechanisms around shallow tunnels in brittle rock
- 2007
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Ingår i: 11th Congress of the International Society for Rock Mechanics. - : Taylor and Francis Group. - 9780415450850 ; , s. 883-890
-
Konferensbidrag (refereegranskat)abstract
- As part of an ongoing study on the mechanical characteristics of the damaged rock zone (DRZ) around a tunnel boundary and its influence on the overall behaviour of the near-field host rock, a numerical study was conducted to investigate the dominant rock mass failure mechanisms around shallow tunnels located in a body of brittle rock mass. Preliminary studies have clearly indicated that, the rock mass behaviour was largely dictated by the different yield mechanisms involved. These mechanisms appear to be multifarious due to the complex state of the induced stresses around the tunnel boundary at shallow depth. Some of these yield mechanisms are often difficult to capture using the traditional yield criterion such as the Mohr-Coulomb. In the study reported in this paper a series of computer simulations were performed using typical in-situ stresses and rock mass conditions generally encountered in shallow tunnelling projects in Sweden. The presence of a disturbed/damaged rock zone with finite thickness was also added into the models. Due to the nature of the simulations the FLAC2D code was selected and used. The values for the input parameters were estimated using a systematic procedure. To prevent premature tensile yielding due to transient loading traction was applied during tunnel excavation. The results show that, the dominant yield mechanism occurring around the shallow tunnel in brittle rock is the one of tensile nature. Compressive mechanisms do occur but seems to be less critical to overall performance of the tunnel. However, they do influence the overall behaviour of the rock mass response. The results further indicated that, the ‘true' locality of instability could be predicted from elastic analyses, by observing if all the major principle stresses are in tension in that locality. The shear strain increment plots of the model in plastic mode further supported this observation.
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| 35. |
- Saiang, David, et al.
(författare)
-
Feasibility Study of Alternative Mining Methods : for Kiruna and Malmberget Orebodies
- 2020
-
Rapport (övrigt vetenskapligt/konstnärligt)abstract
- The aim of this study is to investigate alternative underground mining methods at depth for LKAB’s Kiruna and Malmberget orebodies. These methods can be complementary to the Sublevel Caving (SLC) currently applied the mines. At the conclusion of this study a recommendation is to be made for further investigation into selected alternative mining methods.
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| 36. |
- Saiang, David, et al.
(författare)
-
FLAC3D modelling of rock support arches
- 2020
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Ingår i: 5th International Itasca Symposium - 2020.
-
Konferensbidrag (refereegranskat)abstract
- This paper presents the FLAC3D modelling of rock support arches in trial stope at Boliden's Garpenbergmine in Sweden. The objective was to evaluate the effectiveness of rock support arches in stabilizing theground when rill stopes heights are raised beyond the current heights. Boliden utilizes the Rill miningmethod to mine most of its orebodies that are hosted in poor ground conditions; weak rock and high stresses.This mining method requires the development lower and upper drifts and extracting the block of ore between the drifts by a sequence of benching, mucking and backfilling cycles. The block of ore between thetwo drifts is generally referred to as rill bench. Presently, the rill bench heights are restricted to 10-15 m soas not to expose the stopes to high walls comprising weak rock in high stress field. However, it has beenroutinely observed that, much of the ground deformations appear to occur during the early stages when thelower and upper drifts are developed and significantly diminish when the rill benches are mined. This observation gave the reason to investigate the possibility to raise the rill bench heights, with additional reinforcement provided by rock support arches. Boliden has successfully used rock support arches at theGarpenberg mine as well as in its other mines (Boliden 2016). The view is that, by installing optimallyspaced rock support arches, stable ground conditions can be achieved thereby permitting the rill benchheights to be raised to 20 or 25 m. To test this hypothesis a series of numerical models were run in FLAC3Dwith different rill heights and different arch spacings, along with regular support, to investigate the performance of the arches. These simulations also preceded the field trial to identify the optimum arch spacingand the likely outcome of the field investigations. The field trial itself is presently conducted in the orebodycalled Dammsjön at a depth of 890 m with a rill stope height of 25 m (i.e. 20 m rill bench plus one 5 mdrift). Monitoring of the trial stope is currently on-going. Some initial data from this monitoring have beenmade available for the first pass calibration of the FLAC3D models presented in this paper.
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| 37. |
- Saiang, David, et al.
(författare)
-
Ground support modelling involving large ground deformation : Simulation of field observations – Part 1
- 2016
-
Ingår i: Proceedings of the 8th International Symposium on Ground Support in Mining and Underground Construction.
-
Konferensbidrag (refereegranskat)abstract
- The Kristineberg mine has a long history of large ground deformation which consequently incites ground control problems for the mine. Over the years the mine has developed various mining techniques, backfilling and ground support procedures to manage this problem. In general the ground control problems at the mine are highly influenced by the wall rock geology. The wall rock, that is the footwall and hanging wall, comprise of highly altered chlorite schist, which are internally referred to as talc-schist. They very often occur as seams with thickness barely ranging from 0.1 m to as wide as 3.0 m. Coupled with high ground stresses the talc squeezes and slides into the stope if undercut by the excavation, or either bends or bulges inwards when exposed but not undercut depending on the loading direction. The deformation magnitudes have often been reported to be in the order of 0.2 to 0.5 m and seldom up to 1.0 m. Conventional rock support system, consisting of fibre re-enforced shotcrete and rebar rock bolts, has regularly failed under these conditions. As part of Ground Support Research Initiative at Luleå University of Technology a monitoring program was designed to measure ground deformation and the response of the ground support system. Numerical modelling was conducted to capture the responses as observed during monitoring. The numerical models revealed all the typical mechanisms of instability that have been conceptualized through observations and earlier studies. Talc obviously was the most influential lithology that controlled the deformation characteristics of the stope and ultimately on the rock support system. Combinations of bending, bulging, shearing and tensile mechanisms induced a complex loading pattern on the rock support system. Often the rock bolts, for example, would experience all of these mechanisms at once or during different stages of the excavation rounds as a cut is developed.
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| 38. |
- Saiang, David, et al.
(författare)
-
Ground support modelling involving large ground deformation : Simulation of conceptual cases – Part 2
- 2016
-
Ingår i: Proceedings of the 8th International Symposium on Ground Support in Mining and Underground Construction.
-
Konferensbidrag (refereegranskat)abstract
- As a continuation of Part 1 of ground support modelling involving large ground deformation by Saiang and Nordlund (2016) this paper presents the conceptual models and results from the typically observed cases throughout the Kristineberg mine. The Part 1 of the paper focused primarily on results from measurements carried out at the J-orebody, whereas the Kristineberg mine consists of many ore bodies or lenses within the VMS (volcanic massive sulphides). Part 2 therefore presents some of the typically observed rock mass behaviours throughout the mine. The mine geology is very complex for each of the orebody due to the multiple phases of wall rock alterations and various geological processes that occurred throughout the history of the deposit. This history also included both local and regional events of folding, faulting and shearing. Despite the notable differences in the local geology around the different orebodies, there is nevertheless, a general trend that the stability of the stopes throughout the mine are in principal controlled by the altered wall rocks, the presence of other lithologies capable of inhibiting deformation and the geometry of the stopes themselves as demonstrated in Part 1.
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| 39. |
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| 40. |
- Saiang, David, et al.
(författare)
-
Integrated Storage Facility — A New Concept for Mine Waste Storage
- 2020
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Ingår i: Tailings and Mine Waste 2020. - Vancouver : UBC Studios, University of British Columbia. ; , s. 477-489
-
Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- A new concept for mine waste storage called Integrated Storage Facility has been touted in places where managing mine waste is extremely challenging. Such a concept has been conceived to be pioneered for a massive copper-gold project in Papua New Guinea, where rugged tropical terrains, tough climatic and geological conditions make building of conventional mine waste storage facility one of the biggest challenges in the country. The developer of Frieda River Copper-Gold project in Papua New Guinea, PanAust, plans to create a huge man-made lake, occupying an area of 12,700 hectares and perched between several valleys at an elevation of 400 to 800 m above sea level. This Integrated Storage Facility will serve two functions: (i) submarine environment for underwater storage of mine tailings and waste rock and (ii) hydro-electric facility to power the mine and excess power for export. The facility is planned to hold 2.13 billion cubic meters of tailings and waste rock over the life of the mine, and 0.04 billion cubic meters of water. Since this infrastructure is neither a classical hydro-power dam, nor a tailings dam, the design of the infrastructure was difficult to benchmark against existing hydro-power dams and tailings dams. In view of the nature of the infrastructure the government of East Sepik Province, a stake holder in the project, engaged a team of engineers to carry out high level review of the design cncept of the infrastructure considering the risks and consequences. This paper is the result of this review and highlights some of the challenges facing such a concept.
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| 41. |
- Saiang, David, et al.
(författare)
-
Laboratory tests on shotcrete-rock joints in direct shear, tension and compression
- 2005
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Ingår i: Rock Mechanics and Rock Engineering. - : Springer Science and Business Media LLC. - 0723-2632 .- 1434-453X. ; 38:4, s. 275-297
-
Tidskriftsartikel (refereegranskat)abstract
- A series of laboratory tests was performed on cemented shotcrete-rock joints to investigate the strength and stiffness of the interfaces, while simulating field conditions as close as possible. The direct shear test formed the core of the experimental work, while the tension and compression tests were complementary. To simulate loading conditions experienced in practical cases the direct shear tests were performed under fairly low normal stresses. In most practical cases when shotcrete is used with rock bolts, the normal load on shotcrete lining seldom exceeds 0.2 to 0.5 MPa. The direct shear test results show that, for such normal load range the shear strength is determined by the bond strength for genuinely bonded shotcrete-rock interfaces. For higher normal stresses (σn > 1.0 MPa), which rarely exist at the shotcrete-rock interface, the shear strength is largely influenced by friction resulting in the cohesive strength being less significant. Assessment of the shear surface revealed that the steel fibres in the shotcrete appeared to contribute significantly to the frictional component. The shear and normal stiffnesses of the interface were also determined, which were in principal the stiffnesses of the bond. An interesting observation was the complex interaction at the interface and the mechanisms that controlled the peak shear strength which depended on the surface roughness, the existence of natural flaws and the normal load.
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| 42. |
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| 43. |
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| 44. |
- Saiang, David, et al.
(författare)
-
Numerical analyses of the influence of blast-induced damaged rock around shallow tunnels in brittle rock
- 2009
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Ingår i: Rock Mechanics and Rock Engineering. - : Springer Science and Business Media LLC. - 0723-2632 .- 1434-453X. ; 42:3, s. 421-448
-
Tidskriftsartikel (refereegranskat)abstract
- Most of the railway tunnels in Sweden are shallow-seated (<20 m of rock cover) and are located in hard brittle rock masses. The majority of these tunnels are excavated by drilling and blasting, which, consequently, result in the development of a blast-induced damaged zone around the tunnel boundary. Theoretically, the presence of this zone, with its reduced strength and stiffness, will affect the overall performance of the tunnel, as well as its construction and maintenance. The Swedish Railroad Administration, therefore, uses a set of guidelines based on peak particle velocity models and perimeter blasting to regulate the extent of damage due to blasting. However, the real effects of the damage caused by blasting around a shallow tunnel and their criticality to the overall performance of the tunnel are yet to be quantified and, therefore, remain the subject of research and investigation. This paper presents a numerical parametric study of blast-induced damage in rock. By varying the strength and stiffness of the blast-induced damaged zone and other relevant parameters, the near-field rock mass response was evaluated in terms of the effects on induced boundary stresses and ground deformation. The continuum method of numerical analysis was used. The input parameters, particularly those relating to strength and stiffness, were estimated using a systematic approach related to the fact that, at shallow depths, the stress and geologic conditions may be highly anisotropic. Due to the lack of data on the post-failure characteristics of the rock mass, the traditional Mohr-Coulomb yield criterion was assumed and used. The results clearly indicate that, as expected, the presence of the blast-induced damage zone does affect the behaviour of the boundary stresses and ground deformation. Potential failure types occurring around the tunnel boundary and their mechanisms have also been identified.
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| 45. |
- Saiang, David, et al.
(författare)
-
Numerical Analysis of Large Ground Deformation and Rock Support Interaction at Kristineberg Mine, Sweden
- 2014
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Rapport (refereegranskat)abstract
- Numerical analyses have been performed to study the interaction between rock support and rock mass in response to large ground deformation at the Kristineberg mine. Ground control problems at the Kristineberg mine is known to be highly influenced by the wall rock geology. The wall rock, that is the footwall and hanging wall, comprise of highly altered chlorite schist, which is internally referred to as talc-schist, very often occur as seams with thickness barely ranging from 0.1 m to as high as 3.0m. These material squeeze and slide into the stope if undercut by the excavation or bends inwards if exposed but not undercut. The magnitude of the deformation has often been reported to be in the order of 0.2 to 0.5 m and seldom up to 1.0 m. Conventional rock have support consisting of fibre re-enforced shotcrete and rebar regularly failed under these conditions. A field investigation has therefore been carried out to study the response of the current rock support system to the different mechanisms of instability at the Kristineberg mine. In addition, a new rock bolt type, called the D-bolt, has been tested during the field tests. The numerical study revealed all the typical mechanisms of instability that have been conceptualized through observations. The performance of rebar is clearly affected by the combinations of bending, shearing and tensile mechanisms. D-bolt, on the other hand, is a ductile rock bolt and, its performance appears to sustain large deformations before showing signs of yielding. However, more work needs to be done before proper conclusions can be made about the performance of the D-bolt under such conditions.
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| 46. |
- Saiang, David, et al.
(författare)
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Numerical study of the mechanical behaviour of the damaged rock mass around an underground excavation
- 2008
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Ingår i: MassMin 2008. - Luleå : Luleå tekniska universitet. - 9789163323317 ; , s. 803-813
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Konferensbidrag (refereegranskat)abstract
- The behaviour of the rockmass immediately surrounding an excavation (e.g. open pit slope, underground mine drift, etc.) will ultimately determine the overall performance of the excavation itself and the general operational safety, as well as providing the basis for support requirement decisions. Very often the near-field rockmass is significantly disturbed or damaged by blasting and redistribution of stresses. Any damage or disturbance to the near-field host rock will result in reduction to the strength and stiffness of the rockmass and consequently affect the stability of the excavation. In this paper a series of numerical analyses was conducted to study the behaviour of the near-field host rock, with a damaged rock zone around the excavation boundary. Typical underground mining drift geometry was used in building the models. The in-situ rockmass parameters are those typically encountered in the Swedish hard rockmass system, including the in-situ stresses. The results show that, the stability parameters; induced stresses and ground deformation, were observably affected by the presence of the damaged rock zone, as expected.
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| 47. |
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| 48. |
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| 49. |
- Saiang, David
(författare)
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Simulation of truck haulage queue system at an open mine using SIMIAN
- 2008
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Ingår i: MassMin 2008. - Luleå : Luleå tekniska universitet. - 9789163323317 ; , s. 607-616
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Konferensbidrag (refereegranskat)abstract
- Simulation methods can be used in a variety of queuing situations: boats waiting for an unloading or loading quay, banking tellers, supermarket tills, logs passing through a sawmill, passengers arriving at an international airport and so forth. In mining operations it can be used for example, to simulate flow of ore through a processing plant or the flow of haul trucks in an open pit. The purpose could be for ore blending, equipment optimisation and production target realization. This paper presents the simulation of a truck haulage queue system at a large open pit mine using SIMIAN simulation language. The statistical data used in the model are derived from real time data obtained from a large open pit mine in Papua New Guinea. This mine is also used as a case for the models developed herein. The movement of trucks through the open pit is simulated using the configuration prevalent during the time of data collection.
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| 50. |
- Saiang, David
(författare)
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Stability analysis of the blast-induced damage zone by continuum and coupled continuum-discontinuum methods
- 2010
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Ingår i: Engineering Geology. - : Elsevier BV. - 0013-7952 .- 1872-6917. ; 116:1-2, s. 1-11
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Tidskriftsartikel (refereegranskat)abstract
- The presence of a blast-induced damage zone (BIDZ) around a tunnel boundary is of significant concern mainly with regard to safety, stability, costs and the overall performance of the tunnel. The BIDZ is essentially characterized by reduction in strength and stiffness, and increase in permeability. Guidelines have been developed based on perimeter blasting experiences and overbreak characterization to regulate damage due to blasting. Although the over-break approach of assessing the degree of blast-induced damage is practical, the method does not provide a measure of the competency of the damaged rock. Very often it is important to know how the damaged rock mass will behave under any given conditions. In this paper a series of numerical analyses was performed using continuum and coupled continuum-discontinuum methods to study the behaviour of the blast-induced damage zone. In the coupled continuum-discontinuum method FLAC and PFC2D were coupled together. The inner segment of the model was simulated using PFC2D, while the outer segment was simulated using FLAC. This enabled the tracking of failure and fallout from the PFC2D model. The tunnel was excavated within the PFC2D segment. Blast-induced radial cracks were traced and individually implemented in the models. Models were also run independently in FLAC and Phase2 and the results were compared to those of the coupled models. The results show that the failure around the tunnel was confined in most parts to the damaged zone at shallow depths, but not in deep excavations. The failures and fallouts mapped with the coupled models were consistent with practical observations. Since the continuum models cannot simulate failure, results from the coupled model were used to identify indicators for failure in the continuum models. It was seen that yielding due to volumetric straining (in FLAC) and 100% yielded elements (in Phase2) were consistent with the failures mapped in the coupled models for shallow excavations, but was less consistent for deep excavations
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