Showing papers in "Bulletin of Engineering Geology and the Environment in 2012"
TL;DR: In this article, the authors examined and assessed predictive methods for the saturated hydraulic conductivity of soils and found that most predictive methods were calibrated using laboratory permeability tests performed on either disturbed or intact specimens for which the test conditions were either measured or supposed to be known.
Abstract: This paper examines and assesses predictive methods for the saturated hydraulic conductivity of soils. The soil definition is that of engineering. It is not that of soil science and agriculture, which corresponds to “top soil” in engineering. Most predictive methods were calibrated using laboratory permeability tests performed on either disturbed or intact specimens for which the test conditions were either measured or supposed to be known. The quality of predictive equations depends highly on the test quality. Without examining all the quality issues, the paper explains the 14 most important mistakes for tests in rigid-wall or flexible-wall permeameters. Then, it briefly presents 45 predictive methods, and in detail, those with some potential, such as the Kozeny-Carman equation. Afterwards, the data of hundreds of excellent quality tests, with none of the 14 mistakes, are used to assess the predictive methods with a potential. The relative performance of those methods is evaluated and presented in graphs. Three methods are found to work fairly well for non-plastic soils, two for plastic soils without fissures, and one for compacted plastic soils used for liners and covers. The paper discusses the effects of temperature and intrinsic anisotropy within the specimen, but not larger scale anisotropy within aquifers and aquitards.
270 citations
TL;DR: In this article, the characteristics of tunnel failures were analyzed and categorized as avalanches and landsliding near the tunnels, cracking of the tunnel portals, collapse of the liner and surrounding rock, cracking and dislocation of the lintern, uplift and cracking of ground, deformation and cracking in the preliminary bracing.
Abstract: Many tunnels along the Dujiangyan to Wenchuan highway, located near the epicenter of the 2008 Wenchuan earthquake in China, were damaged severely. The characteristics of the tunnel failures were analyzed and categorized as avalanches and landsliding near the tunnels, cracking of the tunnel portals, collapse of the liner and surrounding rock, cracking and dislocation of the liner, uplift and cracking of the ground, deformation and cracking of the preliminary bracing. The main geological factors influencing the tunnel damage are secondary fractures of earthquake faults, sudden change in soil and rock type, weak rocks and the variable geo-stresses in the host material. The tunnel portals and their slopes, unless fully integrated into the tunnel structures and sufficiently reinforced, are likely to suffer significant distress as a consequence of seismic events. The main mitigation measures proposed are the use of reinforced concrete in the secondary lining in the area of fault zones and injection grouting to reduce the differences where there are sudden changes in the character of the host material.
139 citations
TL;DR: In this paper, the authors discuss the importance of the "locking section" which is key to assessing slope geohazard and to the development of control/mitigation measures, and discuss how large-scale rock landslides are generally accompanied by sudden brittle failure of the locking section along the potential sliding surface.
Abstract: Large-scale landslides in western China are famous for their size, complex formation mechanism and serious destruction. Data were collected from some typical large-scale landslides in mainland China in the 20th century. A number of geo-mechanical models have been identified: the “three sections” model (sliding; tension cracking; shearing), “retaining wall collapse”, “horizontal-pushing” in horizontal strata; large-scale toppling in counter-inclined strata; the creep-bending–shearing model etc. Large-scale rock landslides are generally accompanied by sudden brittle failure of the “locking section” along the potential sliding surface. The paper discusses the importance of this “locking section” which is key to assessing slope geohazard and to the development of control/mitigation measures.
104 citations
TL;DR: In this paper, a new equation is proposed which uses both dynamic elastic modulus and spatial attenuation of compressive waves to provide an accurate prediction of static Young's modulus.
Abstract: Young’s modulus is one of the most important mechanical parameters in building materials used to assess both the appropriateness of a material as well as its mechanical stability. The paper reports a study to predict the elastic modulus for ten carbonate rocks using the ultrasonic technique. The rocks varied from homogeneous limestones to rocks with abundant stylolite, veins and fissures and were subjected to both salt crystallization and thermal weathering tests in order to modify the number and features of their discontinuities. The dynamic and static elastic moduli were measured in both weathered and unweathered samples. The results confirmed the poor relationship between the static and dynamic moduli for the studied rocks. A new equation is proposed which uses both dynamic elastic modulus and spatial attenuation of compressive waves to provide an accurate prediction of static Young’s modulus. As spatial attenuation is highly sensitive to the presence of rock defects, the correlation is very useful for rocks with fractures, voids and/or which have suffered weathering.
97 citations
TL;DR: In this paper, the authors focused on an area prone to quick clay landslides in mid Norway, which was investigated through a combination of geophysical and geotechnical methods.
Abstract: Mapping of quick clay is important for hazard zonation, planning and protection purposes. The present study focuses on an area prone to quick clay landslides in mid Norway, which is investigated through a combination of geophysical and geotechnical methods. The following classes are suggested for a first-order interpretation of resistivity profiles in areas with few or no previous investigations: Unleached clay deposits: 1–10 Ωm; Leached clay deposits, possibly quick: 10–100 Ωm; Dry crust clay deposits and coarse sediments: >100 Ωm. In the study area, 14–80 Ωm was found as the main resistivity interval for quick clay. The resistivity values from the present study are compared to previously published values. Classification of material from resistivity values is influenced by local conditions, and there is an overlap between the classes. Resistivity profiles can give valuable information for hazard zonation and may assist in maximising subsequent intrusive investigations.
77 citations
TL;DR: In this paper, a comprehensive study of expansive soil behavior includes understanding the surface phenomena of clay particles within the soil matrix, and an approach to approximate surface conductance is presented to predict soil swelling.
Abstract: A comprehensive study of expansive soil behavior includes understanding the surface phenomena of clay particles within the soil matrix. This research studies four micro-scale properties of four remolded expansive soils––matric suction, pH, surface conductance and percentage of montmorillonite––in order to predict soil swelling. An approach to approximate surface conductance is presented. Linear regression analyses were undertaken in an attempt to predict percent swell and swell pressure based on each of these micro-scale properties. Matric suction was found to be the most accurate predictor of the swelling behavior of the studied soils, which were initially compacted at optimum moisture content. Surface conductance, which is a combination of specific surface area, cation exchange capacity and cation mobility, also gave good predictions, except for one soil with high acidity.
55 citations
TL;DR: In this article, a systematic study was carried out to verify the differences between the two techniques for liquid limit determination, examining clayey soils from various geologic units, concluding that the liquid limit obtained by the fall cone method is generally 2.2% points higher than that obtained by hard base Casagrande apparatus.
Abstract: For liquid limit determination, the European Standards require the cone penetrometer technique or, alternatively, the Casagrande cup method; but the latter is widely used in practice. As most European soil classification systems are not adapted to the new European Standards, a systematic study was carried out to verify the differences between the two techniques for liquid limit determination, examining clayey soils from various geologic units. Comparison of 100 liquid limit values ranging between 20 and 50% indicates that the liquid limit obtained by the fall cone method is generally 2.2% points higher than that obtained by the hard base Casagrande apparatus. Comparison of data from different sources consistently indicates that the equation proposed in this study may be useful in revising existing soil classification systems, avoiding problems of soil classification due to the technique used for liquid limit determination.
52 citations
TL;DR: In this paper, the authors report a study which reviews stress-induced instability along the Parbati II headrace tunnel, evaluates the rock mechanical properties directly linked to the stress induced instabilities and back-calculates the magnitude of the in situ stress state using finite element numerical modeling.
Abstract: Tunnels passing beneath deep rock cover (overburden) are subject to instabilities caused by induced rock stresses. In a relatively unjointed massive rock mass the instability is associated with rock spalling/rock bursting, while if the rock mass is weak, schistose, sheared and deformed, squeezing is more likely. This paper reports a study which reviews stress-induced instability along the Parbati II headrace tunnel, evaluates the rock mechanical properties directly linked to the stress-induced instabilities and back-calculates the magnitude of the in situ stress state using finite element numerical modeling. An attempt is made to evaluate the magnitude of the tectonic horizontal stress component and to estimate the rock burst depth-impact. It is emphasized that more cases of tunnel damage should be studied to verify the applicability of the proposed equations and to establish the approximate range of the horizontal tectonic stress component along the Himalayan chain.
50 citations
TL;DR: Based on the engineering geological conditions of the deep foundation pit of the Yishan Road Station of Metro Line 9, Shanghai, China, in situ pumping and recharge tests were carried out as mentioned in this paper.
Abstract: In China, more and more underground structures are being built close to buildings of architectural merit. When installing deep foundations, three ways of controlling seepage are suggested. In Mode III, an installed curtain extends partly into the confined aquifer so that the hydraulic connection between the excavated section and the water in the host material is partly isolated. The combined effects of pumping, curtain efficiency and recharge are discussed. Based on the engineering geological conditions of the deep foundation pit of the Yishan Road Station of Metro Line 9, Shanghai, China, in situ pumping and recharge tests were carried out. The combined effects are similar to the results obtained using a three-dimensional finite difference method (FDM) numerical simulation.
47 citations
TL;DR: In this paper, it was found that the undrained shear resistance for clays increased considerably if the pore fluid had a high or a low pH, and the possible explanation could be the dissolution of Al3+ which acts as a coagulant, increasing the internal shear strength.
Abstract: The undrained shear strength of clays is an important geotechnical parameter used during construction processes. Several laboratory tests were performed on kaolinite and smectite mixed with pore fluids with different pH values. Vane shear tests were carried out and it was found that the undrained shear resistance for clays increased considerably if the pore fluid had a high or a low pH. A possible explanation could be the dissolution of Al3+ which acts as a coagulant, increasing the internal shear resistance. Geochemical computations, Al measurements and ζ-potential experiments were performed to confirm this theory. The research suggests varying the pH may make a useful contribution to soil improvement techniques.
47 citations
TL;DR: In this article, wind tunnel testing was undertaken to determine the aerodynamic parameters involved, from the initial rock slide-fall to its point of impact, and the significance of the air-cushion effect.
Abstract: On the April 9 of 2000, a gigantic rapid rock slide-debris avalanche occurred in Bomi, Tibet. Some 280–300 × 106 m3 of material travelled 10 km within 10 min and dammed the Yigong River, forming a 2.9 × 109 m³ barrier lake. Wind tunnel testing was undertaken to determine the aerodynamic parameters involved, from the initial rock slide-fall to its point of impact. The paper reports the numerical analyses undertaken and discusses the significance of the air-cushion effect. It is concluded that Yigong rapid rock slide-debris avalanche “flew” in the air for about 12.9 s from its detachment from the source to its collision with the floor of the Zamunong gully at 3,317 m asl. The velocity of the avalanche mass at the point of detachment was some 81.8 m/s and the collision velocity approximately 117 m/s.
TL;DR: In this paper, the effects of pipe roofing on surface settlements and evaluates the settlements associated with the twin tunnels in the Istanbul metro in terms of numerical, semi-empirical and measured values.
Abstract: In urban areas, the use of pre-support in shallow tunnels is increasing in order to improve the excavation stability and reduce ground settlements induced by the tunneling. This paper describes the effects of pipe roofing on surface settlements and evaluates the settlements associated with the twin tunnels in the Istanbul metro in terms of numerical, semi-empirical and measured values. FLAC3D was used for the numerical modeling and the method suggested by Herzog for the semi-empirical solution. The numerical results indicate that the tunnel roof formed by the pipe roofing provides a restraining effect, reducing deformation and ground surface settlement by up to 65 %. Herzog’s model yields higher maximum surface settlements than those observed. When modified to include the effect of pipe roofing and the distance between the pipes however, there is good agreement between the direct measurements and the values predicted by the numerical and modified Herzog models.
TL;DR: In this article, the variation in the frozen strength of Shanghai muddy clay with temperature was analyzed and the relationship between microstructure and moisture migration was discussed, showing that the shape and orientation of the pores in samples frozen at −10, −15 and −20°C did not significantly change after the compression testing, although the pore volume increased with decreasing temperature.
Abstract: Artificial freezing is becoming a common method of enhancing soil quality when undertaking large scale underground structures in Shanghai. This paper presents the variation in the frozen strength of Shanghai muddy clay with temperature. SEM studies were undertaken to analyse the shape and size of the pores in the frozen material compared with the undisturbed clay. The results show that compared with undisturbed soil, the shape and the orientation of the pores in samples frozen at −10, −15 and −20°C did not significantly change after the compression testing, although the pore volume increased with decreasing temperature. The relationship between microstructure and moisture migration is discussed.
TL;DR: In this article, an experimental program was undertaken to investigate the effects of multifilament and fibrillated polypropylene fiber on the compaction and strength behavior of CH class soil with fly ash in different proportions.
Abstract: Fly ash is a waste produced from the burning of coal in thermal power stations. The staggering increase in the production of fly ash and its disposal in an environmentally friendly manner is increasingly becoming a matter of global concern. Efforts are underway to improve the use of fly ash in several ways, with the geotechnical utilization also forming an important aspect of these efforts. An experimental program was undertaken to investigate the effects of multifilament and fibrillated polypropylene fibre on the compaction and strength behavior of CH class soil with fly ash in different proportions. The soil samples were prepared at two different percentages of fibre content (i.e. 0.5 and 1% by weight of soil) and two different percentages of fly ash (i.e. 10 and 15% by weight of soil). A series of tests were prepared including optimum moisture content and laboratory unconfined compression strength tests, compaction tests and Atterberg limits test. The fibre inclusions increased the strength of the fly ash specimens and changed their brittle behavior into ductile behavior.
TL;DR: In this paper, a study of the cause of defects in light structures and the toppling of a wall constructed on a fill material rich in Ankara clay was conducted, and the results showed that in the vicinity of the toppled wall, swelling pressures in the horizontal direction were greater than those measured in the vertical direction.
Abstract: The paper reports a study of the cause of defects in light structures and the toppling of a wall constructed on a fill material rich in Ankara clay. Laboratory tests were carried out on vertical and horizontal samples from boreholes and a trial pit was excavated near the damaged structures. The results showed that in the vicinity of the toppled wall, swelling pressures in the horizontal direction were greater than those measured in the vertical direction. The swelling properties of the fill material were higher than those of original Ankara clay as determined previously by other investigators, suggesting that breakdown of the cementing bonds and a change in the fabric are the main factors affecting the swelling pressure of disturbed and compacted expansive soils. The calculations to predict uplift showed a good agreement with the observations in the damaged structures. It is concluded that swelling was the main cause of the damage to the light structures at the study site and resulted from the highly expansive nature of the fill material, poor drainage, the semi-arid climate, poor construction methods and ineffective precautions. Some recommendations for minimizing the effects of swelling at the study site are briefly outlined.
TL;DR: In this paper, the authors evaluate the permeability of the basalts and pyroclastics and the maximum depth of grout injection at the Atasu dam site, Turkey, using the equations of Kiraly and Hoek and Bray based on values obtained from Lugeon tests.
Abstract: This study was performed in order to evaluate the permeability of the basalts and pyroclastics and the maximum depth of grout injection at the Atasu dam site, Turkey, using the equations of Kiraly and Hoek and Bray based on values obtained from Lugeon tests. In order to evaluate maximum discharge values and depth of injection, seepage analyses were performed using the finite element technique for each 10 m up to 100 m. The results indicate that to establish an impermeable zone at the dam site, the depth of injection should be taken as 50 m for the left and right slopes and 40 m for the river bed.
TL;DR: In this paper, an alternative method to diminish adhesion of clays on TBMs was proposed, based on electro-osmotic flow experiments, spectral induced polarisation tests and Zeta-potential simulations.
Abstract: Clogging during mechanical tunnel driving is not only a serious technical issue, but also an economic one. The costs of a tunnel excavation can easily rise and disputes between the awarding authorities and the executive companies may occur. Although the literature is full of cases describing the clogging in clayey soils and despite countermeasures being available, clogging still occurs. This study proposes an alternative method to diminish adhesion of clays on TBMs. Electro-osmotic flow experiments, spectral induced polarisation tests and Zeta-potential simulations were performed on kaolinite and smectite, mixed with several pore fluids under one critical consistency index. The results showed that the electrical parameters were not only influenced by the clay mineralogy per se, but also by the pore fluid chemistry. To apply the laboratory findings in in situ conditions, several theoretical considerations have been taken into account. Although further research is required, the study indicates electro-osmosis may be a new and revolutionary approach to deal with the clogging of TBMs.
TL;DR: In this paper, the authors describe the pedogenically altered fluvial deposits comprising the Barzaman Formation, which is composed of a sequence of rocks dominated by variably cemented conglomerates thought to be middle Miocene to Pliocene in age.
Abstract: This paper describes the pedogenically altered fluvial deposits comprising the Barzaman Formation, UAE. This formation is composed of a sequence of rocks dominated by variably cemented conglomerates thought to be middle Miocene to Pliocene in age. The well-established descriptive scheme currently used for describing the formation is reviewed and a simple visual descriptive lithological classification is proposed based on the three principal lithological components visible in a hand specimen: mottled white calcisiltite matrix/cement, palygorskite rich marl and clasts derived from the Oman Mountains (gabbro, chert and weathered ultramafic rock). Data on the mineralogy and microstructure of the rock constituents is presented and some implications for the geotechnical characterisation of the formation are briefly discussed.
TL;DR: In this paper, a new ground improvement method is proposed for embankment foundation on soft soils, involving the use of both soil-cement columns and prefabricated vertical drains (PVDs) to improve the shear strength and accelerate the preconsolidation process.
Abstract: A new ground improvement method is proposed for embankment foundation on soft soils, involving the use of both soil–cement columns and prefabricated vertical drains (PVDs) to improve the shear strength and accelerate the pre-consolidation process. An analytical solution was derived for calculating the consolidation process of this composite foundation under time-dependent loading by considering the PVDs as cylindrical drain wells. The equivalent coefficient of permeability was acquired by matching the average degree of consolidation of a unit cell model. The analytical expression of consolidation was established according to the axi-symmetric analytical model, and its theoretical solution under time-dependent loading was achieved through the variable separation method. The analytical solution under ramp loading was verified by comparing the calculated results with the three-dimensional finite-element analysis. The influence of replacement ratio of the soil–cement column, column-soil modulus ratio, improvement depth and column-soil permeability ratio were explored. Field experiments on the Huai-Yan Highway indicated the calculated settlements agreed well with the field measurements.
TL;DR: In this paper, a case study dealing with variations on the ground surface due to underground mining activities in the Ostrava-Karvina Coal District (Czech Republic) over the last 25 years is presented.
Abstract: This paper presents a case study dealing with variations on the ground surface due to the underground mining activities in the Ostrava–Karvina Coal District (Czech Republic) over the last 25 years. During this period, some of the areas have experienced settlements of up to 11 m. Seven settlement intervals were used to indicate the varying degrees of subsidence over time. Maps were prepared to show the spatial relationship of the subsidence and to assist in land use planning in this rapidly developing area.
TL;DR: In this article, the Teh and Houlsby's interpretation method has a much higher accuracy for determining the coefficient of consolidation of Quaternary clay deposits while the values of c676 h ≥ 0.
Abstract: The coefficient of consolidation (c
v or c
h) is an important parameter in both geotechnical and geo-environmental engineering, measuring the flow characteristics of soils. In China, conventionally it is obtained from the oedometer test, which is time consuming and of limited accuracy due to inevitable sample disturbance. These difficulties can be overcome by in situ pizeocone dissipation tests which provide continuous measurements of pore water pressure with time. In this paper, existing methods for interpreting coefficient of consolidation in clays from piezocone dissipation tests are briefly reviewed. Piezocone tests were undertaken at different sites in the Jiangsu province of China and piezocone dissipation tests conducted at different penetration depths. Based on the reference c
v values determined from the laboratory oedometer tests, comparisons with existing interpretation methods were undertaken. It is shown that the Teh and Houlsby’s interpretation method has a much higher accuracy for determining the coefficient of consolidation of Quaternary clay deposits while the values of c
h
obtained by the CPTU method are in the range of back-analyzed field values.
TL;DR: In this paper, the authors compared the grain-size distribution of the liquefied soils with empirical bounds of liquefiable soils, and compared the observations with empirical magnitude and epicentral limit distance relations for coherent and disrupted slopes.
Abstract: The Darfield earthquake (Mw 7.1; ML 7.2) occurred along a previously unknown strike-slip fault in Canterbury Province, New Zealand on 4 September 2010. The second (Christchurch) earthquake (Mw = 6.2) on 22 February 2011, caused by a thrust fault, affected the same region. Both earthquakes caused extensive liquefaction, associated ground deformation and severe damage to residential houses and utilities while instability occurred on the Port Hills. In this study, observations by the authors at different parts of the earthquake-affected region after both earthquakes are described, analyzed and discussed. The grain-size distribution of the liquefied soils shows a good agreement with empirical bounds of liquefiable soils. In addition, comparisons of the observations with the empirical relations linking the earthquake magnitude and liquefaction limit distance, show good agreement. The factors of safety against liquefaction are very low when computed by three different techniques using the data from available geotechnical boreholes. Good correlations are obtained between the displacements due to lateral spreading and those estimated from the aerial photogrammetry method, and between the observations with empirical magnitude and epicentral limit distance relations for coherent and disrupted slopes. Estimations using an empirical relation proposed by the authors are compared with lateral spreading and it is concluded that the thickness of liquefiable layers ranges between 4 and 8 m. As the houses and suburban buildings were light, the effect of liquefaction and lateral spreading caused severe damage but not collapse. However, heavy concrete structures settled and tilted and empty buried tanks floated. It is of note that these two earthquakes and major aftershocks greater than magnitude 5 showed that the same areas could liquefy multiple times if the conditions for liquefaction are satisfied.
TL;DR: In this paper, the authors report a study on the capillary barrier effects in a layered pyroclastic deposit with different permeabilities during prolonged low intensity rainfall, such phenomena lead to a significant increase in saturation in the least permeable soil layers.
Abstract: The paper reports a study on the capillary barrier effects in a layered pyroclastic deposit with different permeabilities. During prolonged low intensity rainfall, such phenomena lead to a significant increase in saturation in the least permeable soil layers. This is a common situation on the slopes of Pizzo D’Alvano (Campania, Southern Italy) where severe landslides were triggered in May 1998, and in many other geological environments where geological, sedimentological, geomorphologic and pedological processes may have produced a sequence of soils with different hydraulic conductivity. The results of laboratory column infiltration tests and evidence of capillary barrier effects are presented and used in the calibration of numerical unsaturated flow models.
TL;DR: In this article, three types of polyurethane were synthesized from mixtures of toluene diisocyanate, polyethylene glycol and polypropylene glycol for use in soil stabilization to improve the erosion resistance.
Abstract: Three types of polyurethane were synthesized from mixtures of toluene diisocyanate, polyethylene glycol and polypropylene glycol for use in soil stabilization to improve the erosion resistance. The three polyurethanes were tested at different aqueous concentrations and sand:clay mixtures at weight ratios of 1:1, 1:3 and 1:5. The results of the rainfall simulation, unconfined compression and direct shear tests showed that the polyurethanes improve both strength and erosion resistance significantly. The observed improvement in soil erosion resistance is attributable to the physico-chemical interaction of the long-chain macro-molecules of polyurethane with the clay fraction of the soil.
TL;DR: In this paper, the authors present guidelines for incorporating a geomorphological understanding of landscape evolution into engineering geological practice and discuss how landscape evolution might influence construction contracts and suggest methods for establishing landscape evolution in site investigations.
Abstract: Commission 22 was set up following the 10th IAEG Congress to provide guidelines for incorporating a geomorphological understanding of landscape evolution into engineering geological practice and this paper presents the findings of the Commission. The concept arose from the recognition that landscapes are not static entities during the design life of an engineering structure and that anticipating the changes that will occur should be regarded as a fundamental component of the ground model developed for a construction project. Whilst not all aspects of long term landscape evolution fit easily with engineering projects that have a 100 years design life, there are shorter term processes that do require careful evaluation and incorporation in a site investigation. Concepts of landform equilibrium, geomorphological process-response systems, geohazards, climate and lithologically controlled landscapes, and complex landform assemblages within a palimpsest context, all provide important input for the creation of a four dimensional ground model as required by good ground engineering practice. These concepts are explored in this paper in relation to themes that have a long history within engineering geology and ground model development: geohazard assessment, reactivation of relict processes, design life, risk registers, reference conditions, effects of climate change, magnitude and frequency of natural processes, and cost benefit analysis. Some thoughts on how landscape evolution might influence construction contracts are also explored and suggestions made on incorporating methods for establishing landscape evolution in site investigations.
TL;DR: In this paper, the authors compare stress values obtained from Acoustic Emission and Compact Conical-Ended Borehole Overcoring stress measurement techniques applied at an underground limestone mine in Japan, and investigate the effect of rock anisotropy and confining pressure on the Kaiser Effect level which has been used to determine in situ stresses by the acoustic emission technique.
Abstract: The purpose of the study was to compare stress values obtained from Acoustic Emission and Compact Conical-Ended Borehole Overcoring stress measurement techniques applied at an underground limestone mine in Japan, and to investigate the effect of rock anisotropy and confining pressure on the Kaiser Effect level which has been used to determine in situ stresses by the Acoustic Emission technique. Initially, Acoustic Emission tests were carried out on limestone cores extracted from horizontal boreholes in a pillar and hanging wall in the underground mine. The stress values obtained were two or three times greater than those obtained by the Compact Conical-Ended Borehole Overcoring method. In the second stage, the anisotropy of a granite block was determined by P-wave measurements. Core specimens extracted from two different directions were pre-loaded under axisymetric triaxial conditions by applying a series of differential stresses. The cores were then re-loaded under uniaxial conditions and the Kaiser Effect levels were determined. It was concluded that both the anisotropy and confining pressure have an important influence on the Kaiser Effect level.
TL;DR: In this paper, the use of kinematic stability and slope mass rating (SMR) maps in GIS based on field studies recording the relationships between the bedding/joint geometry relative to the orientation of the free face was discussed.
Abstract: The paper discusses the use of kinematic stability and slope mass rating (SMR) maps in GIS based on field studies recording the relationships between the bedding/joint geometry relative to the orientation of the free face. The results indicated the potential for both planar and wedge type failures in many locations along a railway route. Whilst the results showed the procedure to be a useful first assessment of slope stability, it is recommended that the construction of the maps by kinematic slope stability and SMR analysis within the GIS medium should be used in conjunction with more sophisticated slope stability models taking into account of the material strengths, hydrostatic pressures, seepage forces, active forces, passive forces, etc.
TL;DR: In this paper, two different methods were adapted to create debris flow and rockfall/rock slide susceptibility maps, and success rate curves were calculated for extrapolated zones of initiation for debris flow.
Abstract: The Sea to Sky corridor stretches over a distance of 135 km into British Columbia’s Coast Mountains. The corridor has witnessed hundreds of historical and pre-historic landslides. In the last 154 years, 155 landslide events have been reported. The most common types of landslides are rockfalls and debris flows, which are small in volume, but can be quite damaging. These are more abundant in the southern part of the corridor where infrastructure is built close to steep slopes. Two different methods were adapted to create debris flow and rockfall/rock slide susceptibility maps. Both qualitative heuristic and fuzzy logic susceptibility maps showed a similar distribution of susceptibility zones, especially high susceptibility. Correlation of high susceptibility zones with occurrence of historical and mapped geological landslide events was very good. Success rate curves were calculated for extrapolated zones of initiation for debris flow and rockfall/rock slide deposits. Success rate curves were better for debris flow than rockfall/rockslide maps.
TL;DR: In this article, the results from the smeared rotating crack model were closer to the experimental results than those from the cohesive crack model, and the experimental and numerical analyses were compared.
Abstract: Brazilian tests were conducted on an isotropic limestone with different length-to-diameter ratios and various bearing strip widths. The direct tensile strength of the rock specimens was also obtained using direct tension test apparatus and a servo-control testing machine. The Brazilian test was modeled using the computer program (Abaqus 6.7-1) and both smeared rotating crack and cohesive crack models were selected for the analysis of crack propagation. Comparison of the experimental and numerical analyses showed that the results from the smeared rotating crack model were closer to the experimental results than those from the cohesive crack model. Appropriate testing conditions for the Brazilian test are proposed, in order to achieve the results closest to the direct tension test.
TL;DR: In this paper, the effects of parallel and variable directional joints on ultrasonic pulse propagation in two 60 × 60 × 360 mm prismatic marble blocks containing no joints, six parallel joints, and six variable directional joint.
Abstract: Experiments have been conducted to determine the effects of parallel and variable directional joints on ultrasonic pulse propagation in two 60 × 60 × 360 mm prismatic marble blocks containing no joints, six parallel joints, and six variable directional joints. The results indicated that the attenuation increases with increasing ratio of joints in both models, but the attenuation ratio was higher for the variable directional jointed model than for the model with parallel joints. The relationships between the number of joints and ultrasonic pulse velocities were statistically investigated and the results were evaluated with those found in literature.