Hasil untuk "Engineering geology. Rock mechanics. Soil mechanics. Underground construction"

Ruilin Yang

Abstract Predicting rock blasting outcomes in mining has been crucial since its inception. Blasting remains the most energy‐ and cost‐efficient method for rock breaking and is often the only practical option. However, the mechanism is complex, influenced by various rock properties, explosives, and blast design parameters, making their effects difficult to quantify. Traditional stress‐based models struggle with many parameters, such as stress and Poisson's ratio, which are challenging to measure in the field. Empirical models, though simpler, often oversimplify blast conditions. Both types of models are limited to simulating a few blastholes and cannot handle full‐scale blasts involving hundreds of blastholes. However, modeling full‐scale blasts with all blast design parameters is most required for modern mining applications. This paper presents a novel strain‐based modeling approach for blasting and geomechanical applications, utilizing measurable variables such as particle velocity, strain, and displacement. By bypassing complex constitutive relations, strain‐based models capture critical blasting trends and simulate full‐scale blasts with full‐blast design parameters with minimal calibration. The framework encompasses field strain measurements, model construction based on measurable variables, and laboratory‐derived strain‐failure criteria, each offering potential for future enhancement. Additionally, a standardized field test for site characterization is recommended. The approach is demonstrated through the Multiple Blasthole Fragmentation model, which simulates rock fragmentation and fragment strain during blasting, highlighting the practicality and effectiveness of strain‐based modeling for multiple blasthole blasts. Moreover, this approach extends beyond blasting, with potential applications in highwall stability monitoring and other geomechanical applications. Strain‐based modeling provides a simplified yet effective solution, avoiding the complexities of rock constitutive relations and field stress measurements while enabling full‐blast design simulations for large‐scale field blasts.

Wenhui Bian, Kexue Wang, Jun Yang et al.

The negative Poisson’s ratio (NPR) bolt is an innovative support element distinguished by its high strength, elongation, and a slightly negative Poisson’s ratio. Unlike conventional prestressed (PR) bolts with a positive Poisson’s ratio, the NPR bolt exhibits a quasi-ideal plastic response without a prominent yield platform, enabling it to sustain high prestress with a substantial safety margin, which is particularly advantageous for jointed rock masses. However, investigations into the shear resistance mechanisms of NPR bolts under varying prestress levels remain limited. This study conducted full-scale double shear tests to assess the shear strength, deformation behavior, energy absorption, and failure mechanisms of NPR bolts under different prestress conditions. To ensure a fair comparison with PR bolts, a prestress utilization coefficient (PUC) was introduced. The results reveal that at a PUC of 0.25, the NPR bolt achieved peak axial force, shear displacement, and peak shear force values that are 2.41, 1.88, and 2.13 times greater than those of the PR bolt, respectively. Shear performance was optimized at a prestress level of 100 kN, with energy absorption reaching 47.1 kJ, which is 2.8 times that of the PR bolt. Furthermore, the necking ratio was significantly reduced, indicating more distributed plastic deformation and delayed failure. Field applications verified the superior performance, resulting in a 27.4% reduction in roof settlement and enhanced structural integrity. These findings confirm that NPR bolts possess excellent shear resistance, energy absorption, and deformation adaptability, and optimizing prestress significantly enhances their support performance, providing a strong basis for geotechnical engineering applications.

Kyrillos Ebrahim, Tarek Zayed, Ridwan Taiwo et al.

Gang Wei, Feifan Feng, Shiyu Huang et al.

To explore the load-bearing performance and the failure patterns of the lining structures, a full-scale loading test on the three-ring staggered assembled shield tunnel segments is carried out through a hydraulic loading system. In the experimental study, the segments’ internal force, convergence deformation, and displacement, and the bolts’ internal force, are analyzed. According to the experimental results, the relationship between internal force and deformation is obtained to determine the residual bearing capacity of the shield tunnel at each stage. Three stages are specified for the evolution of the segment’s maximum bending moment during the loading process, in which, the elastic stage is the main and longest stage, in which the bending moment of the segment increases the most. There are two stages for convergence deformation development and segment misalignment development. At the end of loading, the segment’s maximum positive and negative convergence values reach 61.22 and −57.69 mm, respectively. Besides, the maximum segment misalignment is 3.67 mm, which occurs in the direction of 90°. The segment cracks when its maximum convergence value reaches 25.03 mm. Moreover, there are signs of fracturing on the waist joint of the segment when its maximum convergence value reaches 32.73 mm. The concrete at the waist joint starts fracturing in pieces when the segment’s maximum convergence value reaches 38.93 mm, which is defined as the type of shear failure. Finally, the bearing capacity of shield tunnels during segment failure period can be evaluated by using the corresponding relationship between deformation and internal force.

HU Haifeng, LI Peng, CHEN Minghao et al.

To clarify the evolution law of sandstone pore structure under water pressure and reveal its dynamic change mechanism, an experimental study was conducted using nuclear magnetic resonance (NMR) technology. First, sandstone specimens with a size of 50 mm×25 mm were prepared and grouped; after pretreatment such as cleaning and drying, different water saturation pressures (5, 10, 20 MPa) and water saturation times (2, 4, 6, 8, 48 h) were set. Then, the NMR system was used to test parameters such as T2 spectrum, porosity, and water content of sandstone under different conditions, and the variation characteristics of pore structure were analyzed. Finally, the variation law of T2 spectrum was discussed from the perspective of physical mechanism, and its engineering application directions were sorted out. The results show that the amplitude of NMR T2 spectrum signals varies under different water pressures; as the water saturation pressure increases, the T2 spectrum curve shifts to the right with a decreasing shift amplitude, and the T2 spectrum area is positively correlated with porosity and water saturation pressure but with a decreasing growth rate; the water content and pore volume of sandstone increase rapidly within t=0~4 h, and the pore structure tends to be stable after t≥6 h; under the same water saturation time, the increase in water pressure causes damage inside the rock, and after the pressure reaches 10 MPa, the pore structure becomes stable and the rock is completely damaged; the higher the water content of sandstone, the better the pore connectivity and the lower the strength.

Dave O’Leary, Dave O’Leary, Cosimo Brogi et al.

IntroductionThe mapping of soil properties, such as soil texture, at the field scale is important Q6 in the context of national agricultural planning/policy and precision agriculture. Electromagnetic Induction (EMI) surveys are commonly used to measure soil apparent electrical conductivity and can provide valuable insights into such subsurface properties. MethodsMulti-receiver or multi-frequency instruments provide a vertical distribution of apparent conductivity beneath the instrument, while the mobility of such instruments allows for spatial coverage. Clustering is the grouping together of similar multi-dimensional data, such as the processed EMI data over a field. A neural network clustering process, where the number of clusters can be objectively determined, results in a set of one-dimensional apparent electrical conductivity cluster centers, which are representative of the entire three-dimensional dataset. These cluster centers are used to guide inversions of apparent conductivity data to give an estimate of the true electrical conductivity distribution at a site.Results and discussionThe method is applied to two sites and the results demonstrate a correlation between (true) electrical conductivity with soil texture (sampled prior to the EMI surveys) which is superior to correlations where no clustering is included. The method has the potential to be developed further, with the aim of improving the prediction of soil properties at cluster scale, such as texture, from EMI data. A particularly important conclusion from this initial study is that EMI data should be acquired prior to a focused soil sampling campaign to calibrate the electrical conductivity – soil property correlations.

Maolin Tian, Shaojie Chen, Lijun Han et al.

Abstract The fractured surrounding rocks of roadways pose major challenges to safe mining. Grouting has often been used to reinforce the surrounding rocks to mitigate the safety risks associated with fractured rocks. The aim of this study is to develop highly efficient composite ultrafine cement (CUC) grouts to reinforce the roadway in fractured surrounding rocks. The materials used are ultrafine cement (UC), ultrafine fly ash (UF), ultrafine slag (US), and additives (superplasticizer [SUP], aluminate ultrafine expansion agent [AUA], gypsum, and retarder). The fluidity, bleeding, shrinkage, setting time, chemical composition, microstructure, degree of hydration, and mechanical property of grouting materials were evaluated in this study. Also, a suitable and effective CUC grout mixture was used to reinforce the roadway in the fractured surrounding rock. The results have shown that the addition of UF and US reduces the plastic viscosity of CUC, and the best fluidity can be obtained by adding 40% UF and 10% US. Since UC and UF particles are small, the pozzolanic effect of UF promotes the hydration reaction, which is conductive to the stability of CUC grouts. In addition, fine particles of UC, UF, and US can effectively fill the pores, while the volumetric expansion of AUA and gypsum decreases the pores and thus affects the microstructure of the solidified grout. The compressive test results have shown that the addition of specific amounts of UF and US can ameliorate the mechanical properties of CUC grouts. Finally, the CUC22‐8 grout was used to reinforce the No. 20322 belt roadway. The results of numerical simulation and field monitoring have indicated that grouting can efficaciously reinforce the surrounding rock of the roadway. In this research, high‐performance CUC grouts were developed for surrounding rock reinforcement of underground engineering by utilizing UC and some additives.

Manchao He, Tai Cheng, Yafei Qiao et al.

Rockburst is becoming a huge challenge for the utilization of deep underground space. Extensive efforts have been devoted to investigating the rockburst behavior and mechanism experimentally, theoretically, and numerically. The aim of this review is to discuss the novel development and the state-of-the-art in experimental techniques, theories, and numerical approaches proposed for rockburst. The definition and classification of rockburst are first summarized with an in-depth comparison among them. Then, the available laboratory experimental technologies for rockburst are reviewed in terms of indirect and direct approaches, with the highlight of monitoring technologies and data analysis methods. Some key rockburst influencing factors (i.e. size and shape, rock types, stress state, water content, and temperature) are analyzed and discussed based on collected data. After that, rockburst theories and mechanisms are discussed and evaluated, as well as the microscopic observation. The simulation approaches of rockburst are also summarized with the highlight of optional novel numerical methods. The accuracy, stability, and reliability of different experimental, theoretical and numerical approaches are also compared and assessed in each part. Finally, a summary and some aspects of prospective research are presented.

Xusheng Wang, Yonghua Xie, Chongxi Chen

Objective Both the classical Dupuit model and the modified Dupuit model including infiltration are influenced by Dupuit's assumption and have potential systematic errors. Building a numerical model of well flow in an unconfined aquifer by characterizing the three-dimensional or axisymmetric two-dimensional (2D) flow is an essential approach to verify the performance of Dupuit-type models. Methods In this study, a 2D numerical model is proposed for the steady state well-flow in an unconfined aquifer, in which the control equation of seepage in the cylindrical coordinates is transformed equivalently to the Cartesian coordinates through parameter transformation, and the sectional 2D modelling is implemented via the MODFLOW finite-difference grid of cubic blocks. In the numeric model, the water level in the pumping well is a given condition, the flux across the seepage face is estimated by difference equation according to Darcy's law, the phreatic surface is identified by the treatment of dry and wet cells in MODFLOW, and the pumping rate is determined from the water debug calculation. Results Fine grids are constructed innumerical models of typical cases to obtain high-precision results, in which the relative error of the backwards estimated pumping rate is no more than 0.2%. This numerical model is used to check the Dupuit-type well-flow models. As indicated, the groundwater level estimated from the analytical formulas generally agrees well with the numerical modelling results, except that near the well, where the analytical solution underestimates the groundwater level due to ignoring the waterjump and the errors depend on the anisotropic permeability of the aquifer. When infiltration exists, the flow in the vicinity of watershed does not follow Dupuit's assumption. However, the estimated groundwater level on the watershed by modified Dupuit well-flow equation has a low level of relative error, which is less than 1%. Conclusion This numerical method is simple and practical however it is also influenced by limitations in MODFLOW.

WANG Gao-ang 1, ZHU Si-tao 1, JIANG Fu-xing 1, LI Shi-dong 2, LIU Jin-hai 3, ZHOU Tao 2, NING Ting-zhou 4, LI Huan 2, KONG Zhen 2

In view of the present situation of frequent rock burst appearances of isolated coal body in coal pillar areas of high-stress roadways without obvious mining disturbance, taking the coal pillar of the high-stress thick coal seam in the seventh mining area of Zhaolou Coal Mine in Shandong Province as the engineering background, creep instability rock burst mechanism and prevention technology of isolated coal mass in roadways of high-stress thick coal seam are investigated though theoretical analysis, numerical simulation and on-site investigation. Firstly, the stress evolution laws induced by unstable creep instability of the surrounding rock and the isolated coal body in the roadways of high-stress thick coal seam are studied. Secondly, the mechanism of rock burst induced by creep instability of isolated coal in high-stress roadways is revealed. The results show that the overall instability rock burst is easily induced, when the concentrated stress in the elastic bearing zone of isolated coal body exceeds its ultimate bearing capacity. Thirdly, the creep instability and rock burst mechanical model for isolated coal body in roadways of high-stress thick coal seam is established, and the mechanical criterion of creep instability and rock burst of isolated coal body in roadways is deduced. Finally, the relevant measures are put forward to prevent and control this type of rock burst. The rationality of the theoretical analysis is verified through field practices.

Gabriel Walton, Sankhaneel Sinha

ABSTRACT: Numerical back analysis is a valuable tool available to rock mechanics researchers and practitioners. Recent studies related to back analysis methods focused primarily on applications of increasingly sophisticated optimization algorithms (primarily machine learning algorithms) to rock mechanics problems. These methods have typically been applied to relatively simple problems; however, more complex back analyses continue to be conducted primarily through ad hoc manual trial-and-error processes. This paper provides a review of the basic concepts and recent developments in the field of numerical back analysis for rock mechanics, as well as some discussion of the relationship between back analysis and more broadly established frameworks for numerical modelling. The challenges of flexible constraints, non-uniqueness, material model limitations, and disparate data sources are considered, and representative case studies are presented to illustrate their impacts on back analyses. The role of back analysis (or “model calibration”) in bonded particle modelling (BPM), bonded block modelling (BBM), and synthetic rock mass (SRM) modelling is also considered, and suggestions are made for further studies on this topic.

Zi-qiang Li, Zheng Li, Wei-wei Huang et al.

A ballastless slab track, which is commonly used in the track structures of heavy-haul railway tunnels, was analysed based on field measurement data of the Fuyingzi Tunnel on the Zhangtang Railway. In accordance with the measured data, the dynamic load thresholds and distributions on the surface and bottom of the ballastless slab track were investigated. A fatigue damage analysis of the ballastless slab track was performed based on the dynamic load time–history curve. The results show that the ballastless slab track can accomplish train load attenuation and reduce the dynamic load from heavy-haul trains by 47.22% from the surface to the bottom. In addition, the distribution at the bottom of the ballastless slab track exhibited a triangular shape, and the dynamic load threshold at the line centre accounted for 78.67% of that at the track position. Meanwhile, the distribution at the surface was saddle-shaped; the dynamic load threshold at the track position accounted for 79.55% of that at the line centre position. The fatigue damage of the ballastless slab track was analysed effectively by combining the measured data and the linear fatigue damage theory. Moreover, the accuracy of the calculation results was verified based on the measured dynamic stress of the ballastless slab track structure. The dynamic action of the train load led to more-concentrated damage to the track bed, and the damage occurred earlier than that in the ordinary line. The axle load was the primary influencing factor of the track bed fatigue damage, and the damage mainly occurred in the track position. These results provide a theoretical basis for performing stress analysis and designing parameters for ballastless slab tracks in heavy-haul railway tunnels.

Mohammed Alzamel, Mamadou Fall, Sada Haruna

Compacted bentonite–sand (B/S) mixtures have been used as a barrier material in engineered barrier systems (EBSs) of deep geological repositories (DGR) to store nuclear wastes. This study investigates the individual and combined effects of different chemical compositions of deep groundwaters (chemical factor) at potential repository sites in Canada (the Trenton and Guelph regions in Ontario), heat generated in DGRs (thermal factor), dry densities and mass ratios of bentonite and sand mixtures (physical factors) on the swelling behavior and ability of bentonite-based materials. In this study, swelling tests are conducted on B/S mixtures with different B/S mix ratios (20/80 to 70/30), compacted at different dry densities (ρd = 1.6–2 g/cm3), saturated with different types of water (distilled water and simulated deep groundwater of Trenton and Guelph) and exposed to different temperatures (20 °C–80 °C). Moreover, scanning electron microscopy (SEM) analyses, mercury intrusion porosimetry (MIP) tests and X-ray diffractometry (XRD) analyses are carried out to evaluate the morphological, microstructural and mineralogical characteristics of the B/S mixtures. The test results indicate that the swelling potential of the B/S mixtures is significantly affected by these physical and chemical factors as well as the combined effects of the chemical and thermal factors. A significant decrease in the swelling capacity is observed when the B/S materials are exposed to the aforementioned groundwaters. A large decrease in the swelling capacity is observed for higher bentonite content in the mixtures. Moreover, higher temperatures intensify the chemically-induced reduction of the swelling capacity of the B/S barrier materials. This decrease in the swelling capacity is caused by the chemical and/or microstructural changes of the materials. The results from this research will help engineers to design and build EBSs for DGRs with similar groundwater and thermal conditions.

Jing Li, Yanian Zhang, Xing Liang et al.

Clayey aquitards are widespread in the coastal plain and they are capable to preserve paleo-saltwater. Its salinity distribution and transport process play an important role on the evolution of aquifer groundwater, yet they have attracted little attention. In this paper, undisturbed clayey samples in seven boreholes along the Jiangsu coastal plain were collected and porewater was extracted by squeezing. Based on the natural tracers Cl- and Br- profiles and numerical simulation, porewater salinity characterization and transport mechanism were analyzed. The results showed that two trends of porewater Cl- variations are observed: one is that Cl- peak value is near surface and decreases with depth; the other one is that the Cl- peak value is at depth of 25 m and decreases towards both ends. Porewater has a Cl- range of 486.2-38 036.7 mg/L and Cl/Br of 72-360(average: 241). The relations between Cl- and Cl/Br ratios and the profile signature indicate that saline porewater is of marine origin, and from the Holocene transgression seawater. Subsequently, they were diluted by freshwater. Aquitard porewater 1-D transport model suggests that the transgression and regression events are dominant for the salinity evolution. Holocene seawater is still trapped in the sediment whereas Pleistocene seawater has been flushed out. In aquitard, diffusion is dominant for solute transport with the vertical velocity of 0.43-15.8 mm/yr and influenced by advection in higher permeability sand layers. The redistribution of paleo-saltwater, in particular, in the condition of groundwater over-extraction, would be the important saline source for aquifer groundwater.

V. V. Chernykh

Research subject. The most frequently utilized fundamental notions in stratigraphy are discussed: concrete section, composite section, the stratigraphic scale, the biochronologic scale, the International Stratigraphic Scale.Materials and methods. The conventional content of these concepts is analyzed. The logical invalidity and negative consequences of the identification of subdivisions of the stratigraphic scale and subdivisions of a section are shown. The study of a section provides a way of obtaining information about the stratigraphic sequence of rock formation and the distribution of evidence of the events included in them, which are necessary for constructing stratigraphic scales. The close connection of the source of the actual data and results of its stratigraphic interpretation is the reason for the traditional identification of the subdivisions of the stratigraphic scale and subdivisions of a particular section.Results. The biochronologic scale inherits from a section the time sequence of occurrences of species of a certain group of organisms selected as the basis of a scale. However, special features of the evolutionary development of organisms do not depend on the composition of the containing deposits and the method of the separation of sedimentary rock sequences. This development makes it possible during the study of many specific sections to establish homotaxis in the distribution of fossils, i.e., to build a biochronologic scale. Thus, the understanding of the scale is a model of the biochronologic calculation of geological time. Like any model, a scale cannot be identical to what it simulates.Conclusion. A precise differentiation of the scale and a section is the basis for drawing correct stratigraphic conclusions. A zone is the smallest subdivision of the biostratigraphic scale. Zones are not divided into parts, are discrete (between adjacent zones there are no time passages), equivalent and are characterized by only the place which it occupies on the scale. The construction of a zone scale precedes the establishment of the material equivalent of the zone - of a stratozone - in the section. Any part of a stratozone is dated by the complete zone. The identification of the zonal scale with a sequence of stratozones in the section does not make it possible to understand the minimum dimensionality of a zone subdivision. The International Stratigraphic Scale (ISS) is defined, based on domestic stratigraphic codes and on foreign reference books, as a stratigraphic sequence of rocks (geological bodies) in total volume without passages and overlaps. In this treatment the ISS is not the scale, but is a complete (composite) geological section of the earth’s crust. The biostratigraphic scale serves as a tool of correlation. The ISS gives only the name of that subdivision, with which a concrete section is compared, and the geological age of the deposits of this section is designated by this name.

Tang Jiawei, Shi Xuelu, Zhang Chunhui et al.

The coal based powder activated carbon was modified by nitric acid, the adsorption properties of activated carbon under different modification conditions was investigated the modified activated carbon obtained under the optimal modification conditions was used for the advanced treatment of landfill leachate to investigated the pollutants removal efficiency with varying different parameters such as input dosage and absorption time.The ratio of mesoporous aperture diameter and absorption properties of activated carbon attained the highest after modification 2 h with the concentration of nitric acid 15% and the temperature of modification 60 ℃.The removal rates of COD, NH₃-N, TN and Cr⁶⁺ were 79.0%, 43.3%, 52.6% and 100%, respectively, when the dosage of modified activated carbon was 4 g/150 mg/L, the adsorption time was 12 h, and the solution pH of 7.And after modification, the removal rate of COD and TN increased by 10.1% and 17.3% compared with previous activated carbon.It was found that the reaction of adsorption and degradation of COD in 12 h was more consistent with zero order reaction when analyzing the kinetics of COD adsorption and degradation.In addition, the nonlinear fitting of degradation process indicates that the degradation process can be simulated and predicted by Logistic function model.A better regenerative result was achieved by using ultrasonic method with the options of pH was 4.5 and ultrasonic time more than 2 h.Taking UV₂₅₄ as reference value, the regenerative post-treatment rate was reduced by 12% compared with the initial using which indicated that the nitric acid modified coal-based activated carbon has good regenerative capacity and could be reused.

Pei-Yun Shu, Hung-Hui Li, Tai-Tien Wang et al.

Intact rock-like specimens and specimens that include a single, smooth planar joint at various angles are prepared for split Hopkinson pressure bar (SHPB) testing. A buffer pad between the striker bar and the incident bar of an SHPB apparatus is used to absorb some of the shock energy. This can generate loading rates of 20.2–4627.3 GPa/s, enabling dynamic peak stresses/strengths and associated failure patterns of the specimens to be investigated. The effects of the loading rate and angle of load applied on the dynamic peak stresses/strengths of the specimens are examined. Relevant experimental results demonstrate that the failure pattern of each specimen can be classified as four types: Type A, integrated with or without tiny flake-off; Type B, slide failure; Type C, fracture failure; and Type D, crushing failure. The dynamic peak stresses/strengths of the specimens that have similar failure patterns increase linearly with the loading rate, yielding high correlations that are evident on semi-logarithmic plots. The slope of the failure envelope is the smallest for slide failure, followed by crushing failure, and that of fracture failure is the largest. The magnitude of the plot slope of the dynamic peak stress against the loading rate for the specimens that are still integrated after testing is between that of slide failure and crushing failure. The angle of application has a limited effect on the dynamic peak stresses/strengths of the specimens regardless of the failure pattern, but it affects the bounds of the loading rates that yield each failure pattern, and thus influences the dynamic responses of the single jointed specimen. Slide failure occurs at the lowest loading rate of any failure, but can only occur in single jointed specimen that allows sliding. Crushing failure is typically associated with the largest loading rate, and fracture failure may occur when the loading rate is between the boundaries for slide failure and crushing failure. Keywords: Dynamic strength, Failure pattern, Rock with single planar joint, Loading rate, Angle of load applied

Jingjin Liu, Huayang Lei, Gang Zheng et al.

Problems continue to be encountered concerning the traditional vacuum preloading method in field during the treatment of newly deposited dredger fills. In this paper, an improved multiple-vacuum preloading method was developed to consolidate newly dredger fills that are hydraulically placed in seawater for land reclamation in Lingang Industrial Zone of Tianjin City, China. With this multiple-vacuum preloading method, the newly deposited dredger fills could be treated effectively by adopting a novel moisture separator and a rapid improvement technique without sand cushion. A series of model tests was conducted in the laboratory for comparing the results from the multiple-vacuum preloading method and the traditional one. Ten piezometers and settlement plates were installed to measure the variations in excess pore water pressures and moisture content, and vane shear strength was measured at different positions. The testing results indicate that water discharge–time curves obtained by the traditional vacuum preloading method can be divided into three phases: rapid growth phase, slow growth phase, and steady phase. According to the process of fluid flow concentrated along tiny ripples and building of larger channels inside soils during the whole vacuum loading process, the fluctuations of pore water pressure during each loading step are divided into three phases: steady phase, rapid dissipation phase, and slow dissipation phase. An optimal loading pattern which could have a best treatment effect was proposed for calculating the water discharge and pore water pressure of soil using the improved multiple-vacuum preloading method. For the newly deposited dredger fills at Lingang Industrial Zone of Tianjin City, the best loading step was 20 kPa and the loading of 40–50 kPa produced the highest drainage consolidation. The measured moisture content and vane shear strength were discussed in terms of the effect of reinforcement, both of which indicate that the multiple-vacuum preloading method has a better treatment effect not only in decreasing the moisture content and increasing the bearing capacity, but also in increasing the process uniformity at different depths of foundation.

Simon Heru Prassetyo, Marte Gutierrez, Nick Barton

Experiments on rock joint behaviors have shown that joint surface roughness is mobilized under shearing, inducing dilation and resulting in nonlinear joint shear strength and shear stress vs. shear displacement behaviors. The Barton–Bandis (BB) joint model provides the most realistic prediction for the nonlinear shear behavior of rock joints. The BB model accounts for asperity roughness and strength through the joint roughness coefficient (JRC) and joint wall compressive strength (JCS) parameters. Nevertheless, many computer codes for rock engineering analysis still use the constant shear strength parameters from the linear Mohr–Coulomb (M−C) model, which is only appropriate for smooth and non-dilatant joints. This limitation prevents fractured rock models from capturing the nonlinearity of joint shear behavior. To bridge the BB and the M−C models, this paper aims to provide a linearized implementation of the BB model using a tangential technique to obtain the equivalent M−C parameters that can satisfy the nonlinear shear behavior of rock joints. These equivalent parameters, namely the equivalent peak cohesion, friction angle, and dilation angle, are then converted into their mobilized forms to account for the mobilization and degradation of JRC under shearing. The conversion is done by expressing JRC in the equivalent peak parameters as functions of joint shear displacement using proposed hyperbolic and logarithmic functions at the pre- and post-peak regions of shear displacement, respectively. Likewise, the pre- and post-peak joint shear stiffnesses are derived so that a complete shear stress-shear displacement relationship can be established. Verifications of the linearized implementation of the BB model show that the shear stress-shear displacement curves, the dilation behavior, and the shear strength envelopes of rock joints are consistent with available experimental and numerical results.

I. V. Gaskov

The paper provides the geological, mineralogical, and geochemical characteristics and distribution features of pyrite deposits in Rudny Altai and Southern Urals metallogenic belts. Their similar and different features are elucidated. A common feature of these regions is their close relation to island arc volcanism and large scale of mineralization that forms the world's largest pyrite provinces comparable among themselves and with pyrite belts of different regions of the world. Ore deposits in these regions have a node character and form separate ore areas controlled by volcanic central-type structures and subvolcanic bodies. In general ore deposits have multilayer distribution and are represented by lenticular, rarely tabular bodies, often localized among the hydrothermally altered rocks of quartz-sericite-chlorite and quartz-sericite composition. All deposits are attributed to the pyrite formation and include compositionally similar mineral types such as chalcopyrite-sphalerite-pyrite and gold-barite-polymetallic. Most of the deposits in these regions have a multistage origin and nearly the same mechanism of ore deposition with similar physicochemical conditions of mineralization. The specific of the regions is related to different geodynamic conditions of their formation. The Southern Urals deposits formed within the ensimatic island arcs developed on the oceanic crust while the Rudny Altai deposits occur in the ensialic island arcs developed on the crust of the continental type. This fact is responsible for the difference in volcanism and composition of mineralization.