| 1. |
- Chen, Ming, et al.
(author)
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Failure mechanism of rock mass in bench blasting based on structural dynamics
- 2021
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In: Bulletin of Engineering Geology and the Environment. - : Springer. - 1435-9529 .- 1435-9537. ; 80:9, s. 6841-6861
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Journal article (peer-reviewed)abstract
- This study establishes a multiple degrees-of-freedom structural dynamics analytical model to analyse the influence mechanism of different factors on blasting tight bottom and shape of muckpile. The structural displacement response and distribution of internal forces in the bench rock mass are analysed based on several factors including blasting parameters, explosion load, initiation condition, and geological condition. In addition, the structural failure characteristics of the bench rock mass are studied based on a rock strength criterion. The results indicate that the explosive load strength determines the internal forces of the bench rock mass. The use of blasting parameters with large borehole spacing and small row spacing can increase the internal force and deformation of the bench rock and enhance the effect of the breaking and throwing of rock mass. In addition, the strengthening of the lithology of the bottom rocks or weakening of the lithology of the middle rocks can make destroying the bottom rock mass more difficult and increase the probability of blasting tight bottom formation. Adjusting the initiation point to below the weak-lithology segment of the bench can enhance the internal force and displacement of the bottom rock mass, to improve the blasting effect and avoid blasting tight bottom formation. Combined with the bench blasting field test of the Changjiu limestone mine, it verifies the results of the theoretical analysis of the bench blasting rock mass destruction based on structural dynamics. The results can be used as the theoretical basis and technical support for improving the bench blasting effect.
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| 2. |
- Dehkordi, Seyed Emad, et al.
(author)
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Effect of groundwater flow in vertical and horizontal fractures on borehole heat exchanger temperatures
- 2015
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In: Bulletin of Engineering Geology and the Environment. - : Springer Berlin/Heidelberg. - 1435-9529 .- 1435-9537. ; 74:2, s. 479-491
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Journal article (peer-reviewed)abstract
- Vertical closed loop systems, also known as borehole heat exchangers (BHEs), are a popular way of extracting the ground source heat energy. Primary factors affecting the performance of BHEs are the thermal and hydrogeological properties of the subsurface. Groundwater flow is known to potentially influence heat transport and system performance. The effect of groundwater movement is more commonly studied under homogeneous conditions. However, in heterogeneous fractured rocks, BHEs are more common than horizontal or open loops due to lack of sufficient soil layers and productive aquifers. The finite-element modelling shows that fractures can play an important role in BHE functioning. Especially, vertical open fractures (≥1 mm) near the borehole (≤10 m) can have a considerable impact. Although increase in fracture aperture continuously affects the subsurface and BHE temperatures, the increase in its effect progressively lessens. Depending on the distance and aperture, one major fracture influencing the BHE operation performance can be identified; yet a larger number of fractures may govern heat transport (thermal plume outline) and thermal recovery. Individually, horizontal fractures may have less influence than vertical fractures. However, as the density of horizontal fractures increases, their impact can be major, exceeding that of fracture aperture. In particular, we propose that measurements of rock thermal properties be combined with fracture mapping, to better analyse the thermal response testing results and integrate the configuration of fractures in design and layout of the BHE(s). This is particularly valid for (vertical) fractures not intersecting with the borehole.
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| 3. |
- Ghaderi, Abdolvahed, et al.
(author)
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An artificial neural network based model to predict spatial soil type distribution using piezocone penetration test data (CPTu)
- 2019
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In: Bulletin of Engineering Geology and the Environment. - : SPRINGER HEIDELBERG. - 1435-9529 .- 1435-9537. ; 78:6, s. 4579-4588
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Journal article (peer-reviewed)abstract
- Soil types mapping and the spatial variation of soil classes are essential concerns in both geotechnical and geoenvironmental engineering. Because conventional soil mapping systems are time-consuming and costly, alternative quick and cheap but accurate methods need to be developed. In this paper, a new optimized multi-output generalized feed forward neural network (GFNN) structure using 58 piezocone penetration test points (CPTu) for producing a digital soil types map in the southwest of Sweden is developed. The introduced GFNN architecture is supported by a generalized shunting neuron (GSN) model computing unit to increase the capability of nonlinear boundaries of classified patterns. The comparison conducted between known soil type classification charts, CPTu interpreting procedures, and the outcomes of the GFNN model indicates acceptable accuracy in estimating complex soil types. The results show that the predictability of the GFNN system offers a valuable tool for the purpose of soil type pattern classifications and providing soil profiles.
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| 4. |
- Ghorbani, Sasan, et al.
(author)
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A new rock hardness classification system based on portable dynamic testing
- 2022
-
In: Bulletin of Engineering Geology and the Environment. - : Springer. - 1435-9529 .- 1435-9537. ; 81:5
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Journal article (peer-reviewed)abstract
- Hardness is one of the critical physical characteristics of minerals and rocks, which indicates the resistance of the rock to penetration, scratch, or permanent deformation. As a basic concept, rock hardness has a significant role in rock mechanics and geological engineering and is an appropriate diagnostic tool for the classification of minerals and rocks. The main purpose of this study is to guide rock engineers to measure the rock hardness faster, easier, and more accurately using Leeb’s dynamic hardness test. Accordingly, this paper presents a new rock hardness classification system based on the Leeb dynamic and portable hardness testing method. It is a well-known method for its fast and straightforward procedure testing equipment. A set of 33 different rock types were collected and tested during this study. Next, in-depth microscopic mineralogical studies were performed to determine the precise Mohs hardness value. The Mohs hardness was considered the leading hardness benchmark during the experimental studies, and the Leeb hardness was adopted to classify based on this hardness. A series of laboratory studies and statistical analysis was performed to predict the Shore and Vickers hardness using Leeb hardness. Finally, based on the comparative studies, it is recommended to classify the rocks considering the Leeb hardness method in six different categories: extremely soft (1–250), soft (250–450), moderately soft (450–750), moderately hard (750–850), hard (850–920), and extremely hard (920–1000). The provided classification could be useful in a vast range of rock engineering applications, especially for feasibility studies of rock engineering projects and engineering geology.
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| 5. |
- Gui, Jing Yun, et al.
(author)
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Analytical and experimental studies on toppling behavior of blocks misaligned with the slope face
- 2024
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In: Bulletin of Engineering Geology and the Environment. - : Springer Nature. - 1435-9529 .- 1435-9537. ; 83:4
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Journal article (peer-reviewed)abstract
- The stability of potentially toppling rock blocks has been typically addressed for the case of regular block geometries showing symmetry planes and resting on surfaces aligned with the slope face, i.e., the strike of the slope is parallel to the block sides and their basal planes. However, these simple geometries with ideally oriented blocks are not often found in nature. This study aims to bridge this knowledge gap through analytical and experimental approaches, in the form of laboratory physical models, to study toppling cases for non-conventional scenarios. An engineering geology review was first conducted, identifying potential non-standard cases in nature. Then, the current analytical solutions for both the factor of safety and critical toppling angle were modified for these misaligned cases, focusing on single block and standard block toppling, and considering the effect of block-edge rounding. Physical models support the analytical approach. It is concluded that toppling stability is slightly improved when the orientation of the basal plane of the blocks differs with the strike of the slope. In this way, for single blocks, the critical toppling angle increases a few tenths of a degree when the difference between strikes is 10°, about 1° with strike differences about 20° and 2 to 3° for misalignments about 30°. Similar increases are observed for block toppling cases. Accordingly, small differences in strike of basal planes and the slope contribute to slightly increasing the factor of safety of slopes prone to block toppling. This approach improves practical engineering toppling stability analyses.
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| 6. |
- Hellström, Göran, et al.
(author)
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Seasonal thermal energy storage - The HYDROCK concept
- 2001
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In: Bulletin of Engineering Geology and the Environment. - : Springer Science and Business Media LLC. - 1435-9529 .- 1435-9537. ; 60:2, s. 145-156
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Journal article (peer-reviewed)abstract
- A method for seasonal storage of heat or cold in the bedrock (the HYDROCK concept) is presented and its thermal performance discussed. It involves the use of a fractured bedrock at shallow depths (ca. 50-250 m), where existing fractures are stimulated or new fractures artificially created and used as flow-paths for a heat/cold carrier (usually water). The fracture surfaces are used as heat exchangers and the bedrock is loaded and unloaded to suit the energy needs. Propants are injected into the fractures to keep them open and reduce the energy needed for pumping water through the system. Field tests confirm that stacked parallel fractures can be produced by hydraulic fracturing. The thermal performance of the store is modelled and compared with a ducted ground heat store. It is shown that the HYDROCK store may yield 10-20% more energy during extraction than a ducted ground heat store for similar amounts of injected energy. This indicates that the HYDROCK concept is competitive as a seasonal energy store and may be of particular importance as an alternative energy source where existing methods cannot be economically justified.
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| 7. |
- Kuttah, Dina K, 1975-
(author)
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Assessing the interactions among factors affecting the light-weight deflectometer measurements
- 2023
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In: Bulletin of Engineering Geology and the Environment. - : Springer. - 1435-9529 .- 1435-9537. ; 82:6
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Journal article (peer-reviewed)abstract
- Many different factors can influence the outcomes of light-weight deflectometer (LWD) tests. Some of these factors are specific to the type of the used LWD, while others are related to the testing conditions. This paper summarizes the findings of a detailed investigation into the relationships between variables altering the measurements of the light-weight deflectometer test. Field testing was performed to investigate the effect of the sensing configuration (measurement of plate vs ground surface) and testing configuration (in terms of applied load magnitude, number of loadings, and moisture content). To accomplish this objective, a number of in situ LWD and moisture content investigations were conducted on two selected construction materials, namely, sandy subgrade soil and unbound granular material. Considering the multiple influencing factors involved in this study and the material dependency, relationships between the plate deformations and ground deformations could be developed, something which will help in overcoming the standardization problem of various LWD devices and their effect on the compaction control process. © 2023, The Author(s).
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| 8. |
- Long, Kun, et al.
(author)
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Microcracks development and porosity evolution in sandstone, Sichuan basin, China : an experimental approach
- 2021
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In: Bulletin of Engineering Geology and the Environment. - : Springer Science and Business Media LLC. - 1435-9529 .- 1435-9537. ; 80:10, s. 7717-7729
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Journal article (peer-reviewed)abstract
- The process of fault rupture is closely related to the weakening of fault rock. The weakening process of fault rock from Sichuan basin was investigated when subjected to different loading levels and subsequently unloaded under uniaxial compression. With nuclear magnetic resonance, the transverse relaxation time spectra (T2) distribution and porosity characteristics of the sandstone were quantified; meanwhile, optical microscopic experiments were performed to explore the microcrack growth patterns. According to the growth curve of the normalized porosity, the degradation process of sandstone was divided into three phases. During the first phase, the normalized porosity grew at a small accelerating rate. The intergranular microcracks grew slightly, and there was no distinct change in the number of transgranular and transgranular-intergranular microcracks during this phase, suggesting the weakening was mainly caused by the initiation of new microcracks. In the second phase, the growth rate of the normalized porosity increased linearly as a response to the percentage of failure. At this stage, although intergranular microcracks still dominate, there was a significant increase in the density of transgranular-intergranular microcracks and transgranular microcracks. Furthermore, microcracks developed in parallel with principal stress direction with the increase of the microcrack number and length. In the third phase, the normalized porosity increases at a large accelerating rate. Microcracks continued to grow along the major principal stress direction and penetrate each other. It is noteworthy that the crack density of fault sandstone increased exponentially with load level, and the crack density increased sharply at about 75% of peak strength, suggesting the initiation of fault rupturing. Such results contributed to improve the understanding of porosity change and cracking development of rocks in fault zones, which is pertinent to shear fracture nucleation.
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| 9. |
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| 10. |
- Loorents, Karl-Johan, et al.
(author)
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Free mica grains in crushed rock aggregates
- 2007
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In: Bulletin of Engineering Geology and the Environment. - : Springer Science and Business Media LLC. - 1435-9529 .- 1435-9537. ; 66:4, s. 441-447
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Journal article (peer-reviewed)abstract
- Enrichment of free mica (i.e. as monomineralic grains) in the fine fraction of crushed rock aggregates affects the quality of the aggregate end product. Granitoid rock from the Svecofennian Province were used as being representative of crushed rock aggregates commonly used for construction purposes. The results reveal a general trend of enrichment of mica for finer fractions. For the coarse grained rock a peak occurs at 0.25-0.5 mm followed by a decrease in the amount of free mica; for grains <0.063 mm there is an increase. The general trend and peak are correlated to the microstructural characteristics of the samples.
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| 11. |
- Loorents, Karl-Johan, et al.
(author)
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Trends of enrichment of free mica grains in crushed rock aggregates
- 2009
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In: Bulletin of Engineering Geology and the Environment. - : Springer Science and Business Media LLC. - 1435-9529 .- 1435-9537. ; 68:1, s. 89-96
-
Journal article (peer-reviewed)abstract
- The paper reports a study of the behaviour of free mica grains in crushed rock aggregates of metamorphic origin undertaken to identify any typical trends of enrichment with grain size. The mineralogical composition of the various grain size fractions was obtained using a polarizing microscope and point counting. Two general trends of enrichment of mica are presented: Type I (isotropic source rock) and Type A (anisotropic source rock). Type I is associated with a general increase in free mica towards the finer fraction, with or without a peak for "coarser" grain fractions. Type A is associated with an increase in free mica up to a certain grain fraction, after which there is a decrease with progressively smaller grain size.
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| 12. |
- Magnusson, Mimmi K., 1981-, et al.
(author)
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Geoelectrical imaging in the interpretation of geological conditions affecting quarry operations
- 2010
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In: Bulletin of Engineering Geology and the Environment. - : Springer Science and Business Media LLC. - 1435-9529 .- 1435-9537. ; 69:3, s. 465-486
-
Journal article (peer-reviewed)abstract
- Determination of the subsurface geology is very important for the rock quarry industry. This is primarily done by drilling and mapping of the surface geology. However in Sweden the bedrock is often completely covered by Quaternary sediments making the prediction of subsurface geology quite difficult. Incorrect prediction of the rock-mass quality can lead to economic problems for the quarry. By performing geophysical measurements a more complete understanding of the subsurface geology can be determined. This study shows that by doing 2D-parallel data sampling a 3D inversion of the dataset is possible, which greatly enhances the visualization of the subsurface. Furthermore the electrical resistivity technique together with the induced polarization method proved to be very efficient in detecting fracture frequency, identification of major fracture zones, and variations in rock-mass quality all of which can affect the aggregate quality. With this technique not only the rock-mass quality is determined but also the thickness of the overburden. Implementation of geophysics can be a valuable tool for the quarry industry, resulting in substantial economic benefits.
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| 13. |
- Mossmark, Fredrik, 1975, et al.
(author)
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Hydrochemical impact of construction of the western section of the Hallandsås rail tunnel in Sweden
- 2017
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In: Bulletin of Engineering Geology and the Environment. - : Springer Science and Business Media LLC. - 1435-9537 .- 1435-9529. ; 76:2, s. 751-769
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Journal article (peer-reviewed)abstract
- This paper presents a study of the hydrochemicalchanges that took place during construction of a section ofthe Hallandsa°s rail tunnel in southwest Sweden based onmonitoring from spring 2011 to summer 2012. Leakageinto the tunnel during construction caused lowering of thegroundwater levels, which in turn resulted in a decrease inor absence of base flow in the streams. The water in thestreams became dominated by meteoric water during thedrawdown periods. Meanwhile, wetlands were aerated, andoxygen could penetrate to oxidise reduced S, releasingacids and SO4. The results for the groundwater in thebedrock differed spatially depending on local geologicalconditions. In each of the three monitored boreholes,higher redox potentials, higher concentrations of organicmatter and lower concentrations of dissolved Mn and Fewere observed. In two of the boreholes, oxidation of pyrite,FeS2, present as a fracture mineral, caused the formation ofSO4 and acids with subsequent falls in pH and alkalinity.Leakage into underground constructions generally shortensthe residence time of the groundwater significantly. Silicate weathering would thus become less important for thehydrochemistry compared to processes that occur duringshorter time frames. As regards the durability of the tunnel, the hydrochemical changes observed in two of the three boreholes indicate a more aggressive environment forseveral parameters known to increase corrosivity of steel.The recovery of the groundwater levels occurred rapidlyfollowing completion of the waterproofing systems in theTunnel. However, hydrochemical recovery with regard tomajor ions and pH occurred gradually and with an expectedduration of several years.
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| 14. |
- Olafsdottir, Elin Asta, et al.
(author)
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Hybrid non-invasive characterization of soil strata at sites with and without embedded lava rock layers in the South Iceland Seismic Zone
- 2023
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In: Bulletin of Engineering Geology and the Environment. - : Springer. - 1435-9529 .- 1435-9537. ; 82:4
-
Journal article (peer-reviewed)abstract
- The geological setting of Iceland is unusual, with highly jointed rock mass, loose sediments created in glacial outburst floods and eruptions, and layers of lava rock embedded in or overlying soft sediments. This study aims to assess the feasibility of a composite analysis of dispersion and ellipticity curves for characterization of two of the primary classes of soil sites in the South Iceland Seismic Zone. Specifically, it seeks to develop a cost-effective workflow to identify and characterize sites where a layer of lava rock is embedded in the sedimentary stratum at shallow depth, along with deep soil site characterization. Microtremor HVSR (horizontal-to-vertical spectral ratio) is found to be efficient to distinguish between sedimentary sites with and without an embedded lava rock layer. The results further demonstrate the effectiveness of hybrid ellipticity and dispersion curve inversion to characterize soil sites with an embedded layer of lava rock, which results in a strong velocity reversal with depth. Consistent with previous studies, the hybrid dispersion-ellipticity inversion is also found efficient for characterization of sites with a simpler structure.
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| 15. |
- Pham, Tuan A., et al.
(author)
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Disturbed state concept and non-isothermal shear strength model for unsaturated soils
- 2022
-
In: Bulletin of Engineering Geology and the Environment. - : Springer Nature. - 1435-9529 .- 1435-9537. ; 81:5
-
Journal article (peer-reviewed)abstract
- Shear strength of unsaturated soils is an important engineering property that is required for addressing geotechnical problems, the prediction of which remains to be a challenging task for design engineers due to the complex interaction problem. This study presents a new shear strength equation based on the micromechanical model and the disturbed state concept for unsaturated soils. The original point of this study is considering the solid contact area ratio which was neglected in most of the existing equations. Using the proposed model, the non-linear relationship between the matric suction, saturation degree, and the shear strength of unsaturated soils are described. Validation of the shear strength model was verified against the experimental data and several current models on six different types of soils. The results indicate that the proposed model has a good performance in predicting the shear strength of unsaturated soils, and generally is better than other existing models. In response to varying climatic conditions, the analytical model was then extended to consider the effect of temperature on the shear strength of unsaturated soils. The comparison between predicted and measured results was carried out on compacted silt for three different temperatures. The results show that the proposed model is capable of accurately predicting changes in unsaturated shear strength as a function of temperature.
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| 16. |
- Pusch, Roland
(author)
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Rock sealing with bentonite by means of electrophoresis : [Plombage De Roches A La Bentonite Au Moyen De l’Électrophorese]
- 1978
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In: Bulletin of Engineering Geology and the Environment. - 1435-9529 .- 1435-9537. ; 18:1, s. 187-190
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Journal article (peer-reviewed)abstract
- For special purposes, such as the creation of a practically impervious zone of rock around holes for deposition of highly radioactive waste products, improved techniques for rock sealing are required.Bentonite sealing by means of electrophoretic treatment was investigated in a pilot test using glass plates to simulate rock joints and a small scale experiment on a 1 m3 block of diorite was made as well. It was found that montmorillonite particles could be effectively transported from a bore hole with a dilute bentonite slurry out into joints extending from this hole. The transport of the negatively charged clay platelets was due to an electrical potential field produced by means of electrodes placed in the hole with the slurry (cathode) and in a circumferential row of bore holes (anodes).The electrophoretic treatment largely reduced the permeability of the joints and turned out to be a more effective sealing technique than injection of the same bentonite slurry under pressure only.
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| 17. |
- Ríos Bayona, Francisco, et al.
(author)
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Using PFC2D to simulate the shear behaviour of joints in hard crystalline rock
- 2022
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In: Bulletin of Engineering Geology and the Environment. - : Springer Nature. - 1435-9529 .- 1435-9537. ; 81:9
-
Journal article (peer-reviewed)abstract
- Significant uncertainties remain regarding the assessment of the peak shear strength of rock joints. In recent years, Particle Flow Code (PFC) has been used to simulate shear tests of rock joints. Although previous studies showed PFC's capability to simulate rock joint shear behaviour, it is uncertain how different parameters in PFC should be combined to realistically capture roughness and strength of asperities in contact of actual rock joints. Under low normal stresses, the shear behaviour of well-mated hard crystalline joints is governed by the interaction between asperities of some tenths of a millimetre. This paper investigates the capability of PFC2D to realistically simulate the peak shear strength of hard crystalline rock joints under different constant normal stress magnitudes. The simulated two-dimensional profiles were selected from the digitised joint surface obtained with optical scanning measurements. To realistically capture surface roughness and asperity strength in PFC2D, different values of joint segment length, particle resolution per segment, and bond strength between particles were studied and calibrated while taking into account the laboratory observations. The results of the numerical simulations in the PFC2D environment show that the simulated peak shear strength using the profile containing the steepest asperity is in good agreement with that measured in the laboratory. The joint profile needs to be represented by both a magnitude of segment length that captures the grain size, and at least two particles per segment. The bond strength calibration needs to account for both asperity size and the number of particles in contact during shearing.
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| 18. |
- Robison Fernlund, Joanne
(author)
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Image analysis method for determining 3-D size distribution of coarse aggregates
- 2005
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In: Bulletin of Engineering Geology and the Environment. - : Springer Science and Business Media LLC. - 1435-9529 .- 1435-9537. ; 64:2, s. 159-166
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Journal article (peer-reviewed)abstract
- A new 3-D grain size distribution analysis method for coarse aggregates using image analysis is presented. The method is designed for a laboratory environment and requires no sieving, only imaging of the aggregate. A luminous background material eliminates unwanted shadow effects. Particles are placed so they are not touching, thus the images of the aggregates are of good quality allowing an easy and accurate image analysis with no preprocessing. All three axial lengths of every particle are measured. The results can be plotted either as a continuous curve or showing the axial size of each and every particle. The latter allows the frequency of particles in the tails to be easily evaluated. Good agreement exists between the size distribution curves obtained from the Image Analysis and hand measurements using the Danish Box.
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| 19. |
- Sjodahl, P., et al.
(author)
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Using the resistivity method for leakage detection in a blind test at the Rossvatn embankment dam test facility in Norway
- 2010
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In: Bulletin of Engineering Geology and the Environment. - : Springer Science and Business Media LLC. - 1435-9537 .- 1435-9529. ; 69:4, s. 643-658
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Journal article (peer-reviewed)abstract
- Internal erosion is a cause of embankment dam failure, thus it is important to develop methods for seepage monitoring and internal erosion detection. In order to evaluate the potential of resistivity monitoring to give an early warning of such leakage/erosion, a test was undertaken on a rockfill embankment dam with a central glacial till core at the Rossvatn test facility in Norway. Three defects, consisting of permeable material, were built into the dam at various depths and locations unknown to the personnel carrying out the measurements and data interpretation. A numerical modelling pre-study was carried out, showing that all the actually constructed defects were too small to be detected by single time investigation. In the final test, repeated measurements were undertaken with different reservoir levels, i.e. a limited monitoring approach. This increased the detection capability, confirming the value of the geophysical approach and that monitoring is superior to single time investigations.
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| 20. |
- Spross, Johan, et al.
(author)
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On the observational method for groundwater control in the Northern Link tunnel project, Stockholm, Sweden
- 2014
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In: Bulletin of Engineering Geology and the Environment. - : Springer Science and Business Media LLC. - 1435-9529 .- 1435-9537. ; 73:2, s. 401-408
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Journal article (peer-reviewed)abstract
- For tunnelling in rock in Sweden, the public authorities usually set stringent requirements on low groundwater inflow to the tunnel, to minimise the risk of building settlement and the environmental impact. To improve this groundwater control, the potential application of the observational method in this matter was studied. A comparison was made between the actual implementation of groundwater control in the Northern Link road tunnel project in Stockholm and the definition of the observational method in Eurocode 7. The results showed that the groundwater control in the Northern Link project mainly agreed with the Eurocode. The significance of the deviations was discussed, and it was concluded that adopting the observational method for groundwater control so that it complied with Eurocode 7 would mostly entail simply a formalisation of today's procedures.
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| 21. |
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| 22. |
- Urueña, Cindy, et al.
(author)
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The effect of metamorphism on the aggregate properties of gabbroic rocks
- 2022
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In: Bulletin of Engineering Geology and the Environment. - : Springer Science and Business Media Deutschland GmbH. - 1435-9529 .- 1435-9537. ; 81:5
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Journal article (peer-reviewed)abstract
- Granitic rocks are durable materials sought after for the production of road and railroad aggregates. Granitic bedrock commonly, however, includes gabbroic components, which may enhance or decrease the aggregate performance. This study evaluates the variation in resistance to fragmentation (Los Angeles value, LA) and wear/abrasion (micro-Deval value, MDE) for the fraction 10/14 mm of gabbro in different metamorphic states. Samples were collected along a 150-km profile where metamorphic conditions grade from epidote–amphibolite to high-pressure granulite-facies, and the degree of metamorphic recrystallization varies with the amount of hydrous fluid. Rocks with no or incipient metamorphic recrystallization preserving their primary igneous fabric and interlocking texture meet the criteria for both asphalt base course and track ballast in railroad, with LA and MDE values below 25% and 14%, respectively. Mafic granulite and fine-grained amphibolite have LA values below 25% and can be used in unbound layers. Mafic granulites crystallize at high temperatures but commonly preserve a relict igneous texture due to limited hydration. Coarse-grained amphibolite and migmatitic amphibolite have the poorest performance. They recrystallized at hydrous conditions, leading to complete recrystallization, grain coarsening, and loss of interlocking igneous texture. This study shows that both temperature and infiltration of hydrous fluids significantly affect the technical properties. Even at high metamorphic temperatures, gabbroic rocks may yield aggregates of high technical performance. At hydrous conditions, however, recrystallization results in rock aggregates suitable for unbound layers only. The variation in metamorphic grade and hydration is easily assessed by the geologist in the field and by using standard petrographic microscopy. © 2022, The Author(s).
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| 23. |
- van Eldert, Jeroen, 1987-, et al.
(author)
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Rock support prediction based on measurement while drilling technology
- 2021
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In: Bulletin of Engineering Geology and the Environment. - : Springer Nature. - 1435-9529 .- 1435-9537. ; 80:2, s. 1449-1465
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Journal article (peer-reviewed)abstract
- In tunnelling, rock mass support is designed based on the observed rock mass conditions. These conditions are determined by rock mass characterization. Measurement while drilling (MWD), one such characterization method, acquires drill parameter data during drilling. These data can be used to predict rock mass conditions ahead of the face. In this study, grout-hole MWD data are collected at one of the main tunnels in the large infrastructural project Stockholm bypass tunnels. The normalized and filtered MWD data are correlated to the rock mass characteristics using multilinear regression and the Levenberg-Marquardt method. Although a strong numerical correlation cannot be obtained, the results are promising. As a result, a holistic visual approach, which linked the MWD parameters with the rock mass classification and rock support requirements, was developed.
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| 24. |
- Wang, DongPo, et al.
(author)
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Experimental study on physical model of waste tennis ball-sand composite shed cushion under rockfall impact
- 2022
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In: Bulletin of Engineering Geology and the Environment. - : Springer Science and Business Media LLC. - 1435-9529 .- 1435-9537. ; 81:5
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Journal article (peer-reviewed)abstract
- Given the limited dissipating effect and high construction costs of traditional sand cushion in shed, this paper proposes to partially replace the sand with waste tennis balls to solve the problem of poor impact resistance of sand cushion. Tests of the impact of rockfall on the waste tennis ball-sand composite cushion were carried out exploring the dissipation effect controlled for the following: height of the rockfall, average gas content of the tennis balls, distribution density, whether the tennis ball gaps were filled with sand, and prevalence and position of tennis balls. According to the results, when a steel plate is added above the composite cushion to isolate the river sand and the tennis balls, the peak of reaction force and impact force decreased by 62% and 72%, respectively, and the dissipating effect of the composite cushion is significantly improved. More specifically, the energy dissipation of tennis cushion outperforms the traditional one with an increase of falling height, and the peak value of reaction force and impact force decrease by up to 23% and 14%, respectively. Moreover, under the same impact energy, the dissipating effect of the tennis ball-sand composite cushion gradually increases with the reduction of the gas content of the tennis ball and the distance between the tennis balls; 25% gas content and 5 cm distance have the best energy dissipation effect. The research results can provide new solutions for the structural design of cushion and the reuse of used tennis balls. © 2022, Springer-Verlag GmbH Germany, part of Springer Nature.
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| 25. |
- Weixing, Wang, et al.
(author)
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Rock fracture image acquisition using two kinds of lighting and fusion on a wavelet transform
- 2016
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In: Bulletin of Engineering Geology and the Environment. - : Springer. - 1435-9529 .- 1435-9537. ; 75:1, s. 311-324
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Journal article (peer-reviewed)abstract
- In order to obtain more precise information regarding rock fractures, images of a rock sample using two different light sources were acquired and fused. For image acquisition, an epoxy resin liquid was first injected into a fracture zone in situ, and when the epoxy resin was dry, the rock core sample, including the epoxy resin, was removed from the rock base. The rock core sample was then cut into multiple slices and images of the slices using ultraviolet (UV) and visible lighting were acquired. In order to fuse two slice images, an algorithm based on the redundant lifting, non-separable wavelet transform was studied and utilised. Fusion includes three primary steps for each pair of slice images: (1) applying the redundant lifting, non-separable wavelet transform to each image, and then approximating the two images separately; (2) fusing the approximated images corresponding to the decomposition level using certain rules and fusion operators for obtaining fusion coefficients; and (3) applying the fused wavelet coefficients to the redundant lifting non-separable wavelet transform. The results show that combining the proposed method of image acquisition and the image fusion algorithm is not only effective at obtaining a large volume of detailed rock fracture information, it is also an economical and easy to use method. By applying the new method, rock fractures can be easily detected, and many different parameters in different rock engineering applications can be measured and analyzed.
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