| 1. |
- Abbaszadeh Shahri, Abbas, et al.
(författare)
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CPT-SPT correlations using artificial neural network approach : A Case Study in Sweden
- 2015
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Ingår i: Electronic Journal of Geotechnical Engineering. - : E-Journal of Geotechnical Engineering. - 1089-3032. ; 20:28, s. 13439-13460
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Tidskriftsartikel (refereegranskat)abstract
- The correlation between Standard and Cone Penetration Tests (SPT and CPT) as two of the most used in-situ geotechnical tests is of practical interest in engineering designs. In this paper, new SPT-CPT correlations for southwest of Sweden are proposed and developed using an artificial neural networks (ANNs) approach. The influences of soil type, depth, cone tip resistance, sleeve friction, friction ratio and porewater pressure on obtained correlations has been taken into account in optimized ANN models to represent more comprehensive and accurate correlation functions. Moreover, the effect of particle mean grain size and fine content were investigated and discussed using graph analyses. The validation of ANN based correlations were tested using several statistical criteria and then compared to existing correlations in literature to quantify the uncertainty of the correlations. Using the sensitivity analyses, the most and least effective factors on CPT-SPT predictions were recognized and discussed. The results indicate the ability of ANN as an attractive alternative method regarding to conventional statistical analyses to develop CPT-SPT relations.
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| 2. |
- Andrén, Anna, et al.
(författare)
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Degradation of the Reinforcing Effect of Shotcrete : Freeze-Thaw Tests on Shotcrete-Rock Panels
- 2020
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Ingår i: The Electronic journal of geotechnical engineering. - : Mete Öner. - 1089-3032 .- 1089-3032. ; 25:1, s. 1-30
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Tidskriftsartikel (refereegranskat)abstract
- In rock tunnels in regions with colder climates, the load-bearing structure, including the rock and the reinforcing elements, is exposed to repeated destructive freezing and thawing cycles during the winter. If water accumulates in cracks or in the interface between rock and shotcrete, frost shattering may occur. If there is adequate adhesion between the rock and shotcrete, degradation of the shotcrete as a reinforcement element due to frost shattering should not present a problem. However, if adhesion is poor, a small void will form between the rock and the shotcrete where water can accumulate. If the water in these voids is subjected to freeze-thaw cycles, ice will develop, thus exerting pressure on the interface and causing the shotcrete to crack and degrade. In tunnel sections with complex water conditions, for example, relatively water-bearing open joints and weak zones, the adhesion of the shotcrete and its stability and reinforcing effect may be strongly affected when exposed to freezing temperatures. This article describes a laboratory study that comprised freeze-thaw tests on shotcreterock panels with the objective of studying how water migration affects the growth of ice and the ice pressure in the shotcrete-rock interface to better understand the degradation of the reinforcing effect of shotcrete
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| 3. |
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| 4. |
- Bhanbhro, Riaz, et al.
(författare)
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Mechanical Behavior of Uniformed Tailings Material in Triaxial Tests
- 2017
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Ingår i: Electronic Journal of Geotechnical Engineering. - : Mete Öner. - 1089-3032. ; 22:06, s. 1717-1730
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Tidskriftsartikel (refereegranskat)abstract
- Tailings dams are raised with time depending upon rate of generation of waste. A tailings dam can contain different particle sized materials within its dam body. The newly raised embankment in a tailings dam can be considered as vertical load being applied on subsequent layer. The applied loads can cause deformations and breakage of particles. The particle breakage can then lead to a skeleton with new particle size particles and hence can lead to new material properties. This paper provides the results from triaxial tests conducted on uniformed particle sizes as, 0.5mm-0.25mm, 0.25mm-0.125mm and 0.125mm-0.063mm. The tests are performed at various effective radial stresses. The results are evaluated and compared with each particle size. The results include stress-strain and volumetric behavior during shearing, the effective stress ratio and stress-dilatancy plot. The friction angles are also evaluated and compared with different particle sized specimens. It was found that effective stress ratios were slightly higher when tests were performed at lower confining stresses and vice versa. It was also observed that particle size did not show any effect of friction angles.
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| 5. |
- Bhanbhro, Riaz, et al.
(författare)
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Mechanical Properties of Soft Tailings from a Swedish Tailings Impoundment : Results from Direct Shear Tests
- 2014
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Ingår i: Electronic Journal of Geotechnical Engineering. - 1089-3032. ; 19:Z, s. 9023-9039
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Tidskriftsartikel (refereegranskat)abstract
- The shear strength of tailings can vary depending upon the type of ore and method of construction. Tailings dams may possess loose layers in subsequent layers, which may have low shear strength. Since the tailings dams are made-up to last for longer times, the strength parameters and material behaviors are essential to understand, especially potential for static liquefaction in loose layers. This article presents the results from direct shear tests performed on samples from loose layer of a tailings dam. Both drained and undrained tests are carried out. The results indicated the strain hardening behavior in tailings material which indicates loose condition. The shear strength was found to be relatively low as compared to typical values of tailings in literature. A contractant volume behavior was observed for all the tests. During shear tests the vertical height reductions in samples were observed. These changes were significantly increased after peak shear followed by slight increment in pore pressure along shearing angle. The reasons for these height changes are not fully known, but may be a rearrangement in skeleton or breakage of particles during shear which needs further investigative studies.
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| 6. |
- Deckner, Fanny, et al.
(författare)
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Aspects of Ground Vibrations due to Pile and Sheet Pile Driving
- 2015
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Ingår i: Electronic Journal of Geotechnical Engineering. - : E-Journal of Geotechnical Engineering. - 1089-3032. ; 20:19, s. 11161-11176
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Tidskriftsartikel (refereegranskat)abstract
- Vibrations due to pile and sheet pile driving are part of a complex process involving several factors that influence both vibration magnitude and frequency. Better understanding and prediction of the vibrations generated will greatly benefit the civil engineering practice as well as the construction industry. An important component in understanding vibrations due to pile driving is to comprehend and understand working procedures and the influence of different factors. The objective is to present and discuss factors and working procedures that influence vibrations caused by pile driving, based on three current field tests and formerly presented experience from literature. It is concluded that the factors have the highest impact on ground vibrations due to pile driving are the geotechnical conditions, the vibration generated at the source, the distance from the source and the installation method.
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| 7. |
- Hassellund, Lovisa, et al.
(författare)
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Numerical Simulations of Stability of a Gradually Raised Upstream Tailings Dam in Northern Sweden
- 2016
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Ingår i: Electronic Journal of Geotechnical Engineering. - : Mete Öner. - 1089-3032. ; 21:13, s. 4699-4720
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Tidskriftsartikel (refereegranskat)abstract
- This paper presents a case study where numerical modeling, with the finite element method, has been utilized to assess future stability of a tailings dam in Northern Sweden. The finite element software PLAXIS was utilized to simulate future dike raisings for the years 2024 to 2034. The simulations were conducted by computing each dike raising, the subsequent consolidation of the soil and the stability of the dam during the process. The factors of safety directly after each dike raising resulted in values continuously below a recommended value of 1.5. To increase the dam stability, rockfill berms were stepwise added on the downstream slope of the dam. An optimization technique was applied to place as small volumes of rockfill as possible in the berms at the most suitable locations on the downstream slope. By adding various volumes of rockfill in the berms each year, sufficient stability of the dam was obtained in the simulations. The excess pore water pressures increased annually in the simulations. It was shown that the excess pore water pressures did not totally dissipate before the following dike was constructed. The highest excess pore water pressures were located deep in the impoundment and did not have large effects on the dam stability.
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| 8. |
- 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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| 9. |
- Idris, Musa Adebayo, et al.
(författare)
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The probabilistic estimation of rock masses properties in Malmberget mine, Sweden
- 2013
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Ingår i: Electronic Journal of Geotechnical Engineering. - : Mete Öner. - 1089-3032. ; 18:B, s. 269-287
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Tidskriftsartikel (refereegranskat)abstract
- Numerical modeling techniques have been applied in many mining and civil engineering projects. Traditionally, deterministic methods have been used frequently for the estimation of design or input parameters for numerical modeling. Whereas, it is known that the effect of variability and uncertainty sourced from the complex and variable nature of rock cannot be considered by deterministic approaches using single or mean value. In this paper, the authors tried to apply a probabilistic approach to consider the uncertainties and variability in rock properties. This is to make more a realistic assessment of design parameters of rock masses around an instrumented test drift in Malmberget Mine within the content of the “Rock mass - Rock support interaction project” conducted at the Division of Mining and Geotechnical Engineering, Lulea University of Technology. To calculate the design parameters GSI of rock mass, UCS and mi constant of the intact rock are considered as random variables. For each of these random variables ranges were specified depending on the laboratory and field information. Using Monte Carlo simulation method a possible range of each of necessary strength and deformability properties were obtained and presented. The assessed values can be used as preliminary input parameters and considered as basis for further numerical modeling calibration studies.
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| 10. |
- Jia, Qi, et al.
(författare)
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Effects of Fine Content, Binder Type and Porosity on Mechanical Properties of Cemented Paste Backfill with Co-Deposition of Tailings Sand and Smelter Slag
- 2016
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Ingår i: Electronic Journal of Geotechnical Engineering. - : Mete Öner. - 1089-3032. ; 21:20, s. 6971-6988
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Tidskriftsartikel (refereegranskat)abstract
- Mine backfilling is a process where the underground voids resulted from mining are filled with waste materials. The potential of co-depositing iron sand produced from smelting process with tailings sand was investigated in the present study. Different amounts of iron sand were mixed with the tailings sand to prepare cemented paste backfill (CPB) samples. Two types of binders were used. Uniaxial compression tests were performed for the CPB samples after 28 days of curing. The porosities of the samplers after curing were calculated to correlate the porosity with the uniaxial compression strength, UCS. Results from uniaxial compression tests showed that the amount of iron sand and the type of the binder influences the UCS, as well as content values of fines and porosity. These results demonstrated the possibility for a part of Fe-sand to be deposited together with the tailings sand to increase UCS values for the CPB samples, which will be beneficial for both mining operation and environmental protection.
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