Conducting research on gas migration processes in buffer materials under multi-physics coupling conditions holds both theoretical and practical significance for ensuring the safety of deep geological repositories. Studies reveal that gas migration in buffer materials sequentially undergoes ultra-low permeability and gas breakthrough stages, characterized by gas dissolution-diffusion and significant gas seepage, respectively. The breakthrough mechanisms are categorized into capillary, mechanical, and interfacial breakthrough. To achieve continuous measurement of gas flux throughout the process and identification of breakthrough patterns, experimental setups have evolved through constant-volume, K0 confined, isotropic stress-controlled, and triaxial stress-controlled configurations. The newly developed triaxial testing system enables ultra-low flow rate measurement at 1/10 000 mL/min while incorporating eddy current sensing technology for real-time monitoring of localized volumetric changes in specimens, thereby facilitating breakthrough mode identification. Given the absence of characterization indices in empirical models and quasi-continuum theory-based theoretical models, researchers have established a conceptual model to identify gas breakthrough patterns based on the principle of preferential touching of breakthrough pressure curves. Future research should prioritize gas breakthrough testing methods with short testing cycle and high measurement accuracy, development of generalized breakthrough pattern identification models, and parameter scaling across different scales.

Ecological slope protection combines the benefits of slope safety and ecological restoration, presenting a promising and promotable method for slope protection. The ecological substrate, as the core structural layer of ecological slope protection technology, must exhibit both mechanical strength and vegetative support (mechanical-vegetative performance). The mechanical-vegetative performance of existing ecological substrates requires further improvement, highlighting the necessity for developing new ecological substrates. Nano-SiO₂ (NS) and basalt fiber (BF) demonstrate excellent performance in enhancing the mechanical properties of slope soil. However, research on their vegetative effects and erosion resistance are relatively limited. To address these issues, this study modified clay using two cement contents, four Nano-SiO₂ contents, and three fiber contents. Mechanical, vegetative, and erosion-resistant properties were investigated through unconfined compressive strength tests, direct shear tests, cracking tests, scanning electron microscopy analysis, as well as vegetative growth and erosion resistance tests. The results indicate that adding NS and BF together effectively enhances compressive and residual strength, with the greatest relative improvement at a combination ratio of 5% cement + 0.9% BF + 1.5% NS, achieving a 133.05% increase compared to ordinary cement soil. Additionally, NS and BF significantly improve the cohesion and shear strength of the cement soil. Calcium silicate hydrate (C-S-H) enhances the mechanical interlocking between hydration products and BF by encapsulating the fibers, thereby improving soil strength, crack resistance, and erosion resistance. The pozzolanic reaction and nucleation effect of NS further amplify this improvement. Furthermore, the ecological substrate cement soils with composite ratios of 3% cement + 0.3% BF + 1.5% NS and 5% cement + 0.9% BF + 1.5% NS both achieve germination rate over 80%, meeting planting requirements with good plant growth performance. In the erosion tests, erosion resistance is significantly enhanced, with erosion rates of only 10.24% and 3.60% under the synergistic effect of vegetation.

Current seismic design specifications for reinforced soil retaining walls primarily derive horizontal seismic coefficients from a limited set of model tests or numerical simulations, without considering the influence of facing type on acceleration amplification coefficient distribution. To address this gap, three sets of shaking table tests were conducted on reinforced soil retaining walls with different facing types, using identical soil and geosynthetic materials. The aim was to investigate the frequency-domain distribution of acceleration responses and the effect of facing type on the acceleration amplification coefficient. The test results show that the reinforcement materials significantly improves soil stiffness and integrity, enhancing the amplification of seismic wave components at both low and high frequencies. The acceleration amplification coefficient increases with height along the wall, and the facing type significantly influences its distribution. Specifically, for wrapped retaining wall with low facing stiffness, the acceleration amplification coefficient decreases as peak acceleration increases, reaching a maximum value of 1.69. In contrast, for modular and integral retaining walls with higher facing stiffness, the acceleration amplification coefficient increases with peak acceleration, reaching the maximum values of 1.84 and 1.37, respectively. Based on these findings, this paper proposes a method for calculating the horizontal seismic coefficients of reinforced soil retaining walls with different facing types using the quasi-static method. The results provide valuable insights for seismic stability analysis of reinforced soil retaining walls.

Reasonable determination of active earth pressure is essential for safe and economical design of spatially axisymmetric shafts. Based on the strength equation involving two stress state variables for unsaturated soils and the spatially axisymmetric unified strength theory, a unified strength equation for spatially axisymmetric unsaturated soils was introduced through analogy extension method. Combined with the simplified slip line method, the slip line solution for active earth pressure on shafts in unsaturated soils was derived to capture the intermediate principal stress effect, specifically for uniform and linear suction distributions. Finally, it was validated through a comparative assessment with existing literature, discussing the influence of unsaturated characteristics and intermediate principal stress. The results reveal that the concise formulation of the unified strength equation for spatially axisymmetric unsaturated soils effectively addresses different intermediate principal stress effects, highlighting its theoretical importance. The slip line solution for active earth pressure on shafts simultaneously accounts for both intermediate principal stress effect and unsaturated characteristics, showing good agreement with results for shafts in saturated soils and retaining walls in unsaturated soils reported in the literature. Moreover, it is applicable to uniform, linear and nonlinear suction distributions, and it has broad engineering application prospects. The active earth pressure on the shaft decreases significantly as the matric suction, the intermediate principal stress coefficient, and the unified strength theory parameter increase, especially for uniform suction. Careful selection of the intermediate principal stress coefficient is crucial to prevent large deviations in active earth pressure. The different influencing extents of intermediate principal stress corresponds to different strength criteria for unsaturated soils.

Real-time evaluation of soil compaction quality is crucial for intelligent compaction. To evaluate compaction quality scientifically, the dry density under impact compaction was previously derived by coupling the compaction envelope equation with the equation of motion. The same modeling approach can be applied to vibratory compaction. However, the operating principles of vibratory compaction and impact compaction are different. These differences yield distinct compaction envelope equations for soils under the two conditions. Therefore, this study focuses on deriving the compaction envelope equations for vibratory compaction. By observing the soil’s compressive deformation during vibration compaction and integrating this with theoretical analysis, we establish the compaction envelope equation in a double-logarithmic coordinate system. From the envelope asymptote, we obtain the relationship between peak impact stress and the corresponding pore ratio. Based on the equation of motion for the vibrating steel wheel, the relationship equation between the peak vibration acceleration and the peak impact stress is established. By coupling the above two equations, a real-time equation to predict the dry density of fill soil under vibratory compaction is deduced. Considering the existence of both vertical and lateral deformation on the soil surface during compaction, the resulting real-time dry density equation is approximate. The calculation deviation caused by the difference between the actual constraint conditions and the ideal conditions can be reflected by adjusting the parameters. Finally, the newly proposed real-time dry density formula was applied to the vibratory compaction test to predict the dry density of the soil. The results demonstrate that the newly proposed method for evaluating the quality of fill compaction can accurately predict the dry density of soil under vibratory compaction.

The effects of aerobic degradation on the geotechnical parameters of municipal solid waste (MSW) are complex and variable. As a key parameter of MSW, dry density plays a significant role in assessing the stabilization of aerobic degradation. This study focuses on typical MSW from Wuhan, conducting model tests on six groups under different conditions. The model tests are divided into two parts: anaerobic and aerobic conditions. The results of model tests indicate that water level height, anaerobic storage duration, and aerobic ventilation frequency are key factors affecting the mechanical properties of MSW. The modified primary compression index ranges from 0.174 to 0.452 and is inversely proportional to water level height. During the anaerobic phase, the modified secondary compression index ranges from 0.015 4 to 0.16, whereas in the aerobic ventilation phase, the modified secondary compression index varies from 0.01 to 0.78, showing an inverse relationship with water level height and a direct relationship with aerobic ventilation frequency. Additionally, the aerobic strain efficiency is proposed to characterize the strain characteristics of MSW under varying aerobic ventilation conditions. The aerobic strain efficiercy is directly proportional to aerobic ventilation frequency, while inversely proportional to water level height and anaerobic storage duration. A Logistic model is introduced to describe the variation pattern of organic matter mass in MSW, enabling the prediction of stabilization time for degradation. Finally, based on the strain-settlement model and the mass variation model, a predictive model for dry density of MSW is established.

To reveal the failure mechanism of intermittent jointed rock in deep-buried engineering, true triaxial compression tests of intermittent jointed sandstone with different joint occurrences (dip and strike) were carried out, and acoustic emission (AE) system was used to monitor the failure process of specimens in real-time. The influences of joint occurrence on sandstone failure form, strength, deformation characteristics, AE evolution characteristics, and characteristic stresses were systematically analyzed. The results show that under the condition of true triaxial stress, when the intermittent joint strike is parallel to σ₂, the specimens with joint dip angles of 0°, 30°, and 45° exhibit tensile-shear mixed failure, while the specimens with joint dip angles of 60° and 90° exhibit slipping-shear failure and conjugate shear failure, respectively. When the intermittent joint strike is parallel to σ₃, the failure mode of the samples with different joint angles is “internal shear and external spalling”, indicating that the joint strike has a greater influence on the failure mode of the specimens than the joint dip angles. The strength, crack initiation stress, damage stress, elastic modulus, and peak strain of specimens all decrease first and then increase with the increase of joint dip angle. The strength, initiation stress, damage stress, and peak strain of the specimens with joint strike parallel to σ₂ are lower than those with joint strike parallel to σ₃, and the influence of joint strike on the elastic modulus of specimens is minimal. In addition, the duration of the AE quiet period and the proportion of AE high-frequency signal during this period decrease first and then increase with the increase of joint dip angle. When the intermittent joint strike is parallel to σ₂, the cumulative number of AE hits during the failure process of the specimen decreases first, then increases, and then decreases with the increase of the joint dip angle. When the intermittent joint strike is parallel to σ₃, the cumulative number of AE hits during the failure process of the specimen increases first and then decreases with the increase of the joint dip angle. The research results provide a scientific basis for the failure mechanism analysis of intermittent jointed rock mass and the prevention of engineering geological disasters in deep-buried engineering.

To investigate the relationship between ultra-low friction rock burst and water content characteristics of coal body during mining, a mine in Shenyang was selected as the research object. The water content and water immersion height of coal block and were used to simulate the overall and layered water content characteristics of deep coal body, respectively. The ultra-low friction effect test on deep water-bearing coal block was carried out. The results show that: (1) When the vertical disturbance frequency is 2.0–3.5 Hz, there is a significant influence area for coal blocks with different water contents and immersion heights. Currently, the strength and resistance of ultra-low friction effect change significantly. (2) Compared to dry coal block, when the moisture content of the coal block is 11.7% (natural moisture content), 13.12%, 14.54%, 15.67% and 16.12% (saturated moisture content), the average increasing or decreasing amplitude of the ultra-low friction effect strength is 76.64%, 2.74%, 25.09%, 36.90% and −17.49%, and the average coal-rock interface friction is 5.04, 4.96, 4.74, 4.64 kN and 4.65 kN, respectively. (3) Compared to non-soaking condition, when the coal block is immersed in water at a height of 25, 50 mm and 75 mm, the average increasing or decreasing amplitude of the ultra-low friction effect strength is −16.28%, 19.83% and 100.98%, and the average coal-rock interface friction is 7.30, 6.73 kN and 7.16 kN, respectively. (4) The ultra-low friction effect strength is the highest when the moisture content is 11.7% and the immersion height is 75 mm. It is the weakest when the moisture content is 16.12% and the immersion height is 25 mm. In the actual working conditions, it is necessary to reasonably control the moisture content of coal body and the immersion height to prevent the occurrence of ultra-low friction type rock burst disasters.

Currently, deep shale has become the main position for shale gas exploration and development. As the main battlefield for shale gas development in China, the southeastern region of Chongqing is characterized by unique geological features such as high temperature, bedding development, and strike-slip stress, which limit the high-propagation of hydraulic fractures and severely hinder the stimulation and transformation of shale gas production. Based on this, a large-scale triaxial physical simulation fracturing test on real shale was conducted under the influence of temperature-structure-stress to systematically investigate the influence mechanisms of key parameters, such as temperature, viscosity of fracturing fluid, injection displacement, and in-situ stress difference on the fracturing modification effect. The modification effect of hydraulic fracturing in reservoirs was quantitatively evaluated using the fractal dimensionality calculation method. The results show that under the effect of three control mechanisms, the fracture network morphology after fracturing is characterized by flattening. The thermal shock activated laminae induces fracture steering, which significantly inhibits the expansion of fracture height. The increased stress difference, the use of high-viscosity fracturing fluids, and the construction of high fluid injection displacement can promote fracture expansion across layers. Although the high temperature environment weakens the rupture strength of the rock, it enhances the plasticity characteristics of the rock, resulting in higher extension pressure. The viscosity of the fracturing fluid has a nonlinear regulation on the extension pressure, and the medium viscosity balances the filtering loss effect and viscous resistance to optimize the extension pressure. The analysis of the overall transformation effect of the reservoir shows that high temperature and large-displacement pumping significantly enhance the fractal dimension of the fracture network. The temporary plugging fracturing technique is effective in promoting the volume transformation and improving the complexity of the fracture network. Thermal shock triggers weak tensile extension and generates a large number of microcracks in the bare eye section, and the use of temporary plugging fracturing process can reconstruct the fluid energy distribution and effectively communicate with the unutilized fracture system.

Mineral composition is one of the critical factors regulating the soil-water characteristic curve (SWCC) and micro-pore structure in red soil. The purpose of this study is to analyze the mechanism of mineral composition on the soil-water characteristics of red soil from the microstructural level. The response curve method was employed to systematically evaluate the effects of different mineral compositions on matrix suction, with three key ratios selected for investigation. Using the contact filter paper method, SWCCs were obtained for humidified soil samples with three distinct mineral proportions. Additionally, scanning electron microscopy and mercury intrusion porosimetry were utilized to reveal pore microstructure and distribution characteristics. The results indicate that the regression model constructed using Box-Behnken design demonstrates significant effects of kaolinite and illite on matric suction during variance fitting analysis, whereas montmorillonite exhibits no significant influence. The interaction between kaolinite and illite has a much greater impact on matric suction than the interaction between kaolinite and montmorillonite when a specific variable is fixed. Furthermore, the influence of mineral composition on the SWCC is minimal in the near-saturation and residual regions, where the curve remains relatively flat. In the transition region, the slope of the SWCC increases significantly for samples with high kaolinite content, while the slope is relatively small for samples rich in the other two mineral components. Regarding microstructure, samples with high kaolinite and illite content exhibit uneven sand particle boundaries, large flocculated structures with cross-distribution, and a rich macroporous structure. In contrast, the other two groups of samples display a relatively loose dispersed structure. Moreover, there is a strong correspondence between the dominant pore size range in the pore size distribution curve and the transition region of the SWCC, further validating the profound influence of mineral composition on the soil-water characteristics of red soil.

Mudstone is susceptible to disintegration and argillization when it encounters water. To reveal the evolution of deformation and damage characteristics of mudstone under water-rock interaction, this paper conducts dry-wet cycles experiments on mudstone specimens, collects speckle images of the whole process of experiments by binocular camera, and calculates the three-dimensional displacements and strains on the surface of specimens by using three-dimensional digital speckle correlation software MultiDIC. The results indicate that under dry and wet cycling conditions without externally applied anthropogenic forces, the uneven water absorption and water loss of the mudstone specimen leads to differential expansion and contraction deformation in the adjacent areas. The local tensile strain and shear strain increase significantly in the transition zone of expansion and contraction deformation, where the new crack occurs. The tensile deformation is perpendicular to the crack surface. The direction of shear displacement is along the potential crack surface but perpendicular to the direction of the specimen surface. The specimen shrinks in the center of the specimen when it loses water, while the surrounding area is still expanding due to water replenishment from the center of the specimen. The speed of water loss deformation slows down, but the duration of water loss is longer, and the total deformation is greater than that during the immersion period. As the number of dry-wet cycles increases, the growth rate of crack width and depth first increases, then decreases, and finally tends to be stable. The crack surface becomes a new free surface, with the redistribution of expansion and contraction zones.

Enzyme-induced calcite precipitation (EICP) is an emerging technology used to enhance the mechanical properties of soils and control heavy metal contaminants. However, the differences in the permeability characteristics of graphite tailings with varying particle sizes result in significant variations in mineralization stability and remediation effectiveness. In this study, biopolymer-synergized EICP technology was used to solidify/stabilize graphite tailings. The application potential of chitosan (CTS) in bioremediation of tailings with different particle sizes was explored from both mechanical strength and environmental perspectives. Scanning electron microscopy, infrared spectroscopy, and X-ray diffraction were employed to reveal the underlying mechanisms of tailings solidification/stabilization. The results indicate that CTS-EICP treatment effectively overcomes the limitations of traditional EICP in tailings solidification/stabilization, where treatment effects significantly decrease with decreasing particle size. When the CTS content is 1.5%, the compressive strength and CaCO3 precipitation rate of tailings with particle sizes smaller than 75 μm increase by 210.29% and 150.1%, respectively. After treatment, the pH of the tailings leachate stabilizes at 7.81−8.36, and the reduction in heavy metal ion concentrations ranges from 89.59% to 100%. CTS promotes the formation of carbonate crystals through a urease-stabilized mechanism, with crystals embedding in the three-dimensional network crosslinked by CTS molecules, thereby constructing a composite barrier structure of “tailings-CTS-carbonate-CTS-tailings.” The findings of this study provide valuable insights for the application of EICP in the solidification/stabilization of graphite tailings with different particle sizes.

The compactness of waste residue soil significantly affects its mechanical properties, and it is particularly important to quantitatively analyze the influence of particle gradation on its dry density. The effect of particle size distribution on the dry density of waste slag soil was quantitatively studied by collecting waste slag soil formed by different slag forming methods and conducting particle size distribution and indoor relative density tests. The results show that slag material presents obvious fractal characteristics, with the main gradation curve types being concave and slow S-shaped. Based on the generalized Logistics function and the particle mass fractal model, a two-parameter particle size fractal grading equation is developed. This equation effectively describes the grading characteristics of the waste slag, with parameters a and b adjusting the slope and curvature of the curve. Using the particle size fractal grading equation, the area of the grading curve is integrated, and a prediction model for the extreme dry density of waste slag soil is established. The characteristics of the optimal gradation curve of the waste slag soil and the corresponding parameter range are determined. The research results offer a scientific basis for the stacking design, rolling construction and slope stability analysis of waste slag yards.

Deep-sea polymetallic nodules predominantly exist in semi-buried states within deep-sea sediments characterized by high moisture content and low shear strength. Adhesion characteristic between sediments and nodules is a critical factor affecting collection efficiency. Based on the similarity of physical-mechanical properties in seabed surface sediments, sediment samples were developed to simulate the sedimentary substrate environment for nodule collection experiments. Systematic investigation of adhesion mechanisms was conducted through nodule-simulated sediment pull-out experiments and Coandă-effect-based hydraulic collection experiments. The results indicate that the sediment-nodule contact area and sediment shear strength are the primary factors affecting the adhesion, whereas pull-out speed and jet flow velocity show negligible effects. Moreover, an increase in contact area and higher shear strength enhance the adhesive effect of sediments on the nodules. What’s more, under constant pull-out speed and contact area, the adhesion coefficient exhibits an approximately linear relationship with shear strength. By comparing the results of the pull-out experiment and hydraulic collection experiments, it is found that the adhesion coefficient trends are similar under identical conditions, with a difference of less than 10%, validating methodological correlation. These findings provide valuable insights for the design of hydraulic collection experiments and the optimization of jet parameters in deep-sea mining operations.

The fabric anisotropy of sand significantly affects its mechanical deformation behavior. To accurately characterize this feature, a constitutive model for sand that incorporates fabric anisotropy is proposed, based on the anisotropic critical state theory and the generalized potential theory. First, a variable referred to as virtual peak deviatoric stress is introduced into the hyperbolic model to simulate both the softening behavior of dense sand and the hardening behavior of loose sand. On this basis, the conventional state parameter is replaced with a dilatancy state parameter that captures the evolving characteristics of fabric anisotropy. A stress-strain relationship considering fabric anisotropy is then established in the principal stress space. Subsequently, using the generalized potential theory and the concept of quasi-elastic-plastic deformation, this relationship is extended to the general stress space, leading to the development of a constitutive model that incorporates fabric anisotropy is established. The proposed model is finally applied to simulate drained and undrained triaxial compression/extension tests, as well as hollow cylinder torsional shear tests on Toyoura sand. The simulations demonstrate close agreement with experimental results, confirming the model’s validity. With 13 material constants, the model effectively describes the mechanical behavior of sand across a wide range of stress levels and densities, and successfully captures the influence of fabric anisotropy on its mechanical response.

The excess pore water pressure in silty sand ground is difficult to dissipate and may easily lead to soil liquefaction under wave and seismic loadings. Microbially induced carbonate precipitation (MICP) is an emerging technique for anti-liquefaction soil reinforcement. In this study, a series of undrained hollow cylinder torsional shear tests was carried out. The development of dynamic pore water pressure in saturated MICP-treated silty sand under axial-torsional coupled cyclic shear loads was investigated, considering various influencing factors. Results indicate that the development patterns of dynamic pore water pressure in MICP-reinforced silty sand can be categorized into types A, B, and C. These patterns transition from type A to type C with increasing MICP reinforcement cycles, cyclic resistance stress ratio, and relative density. Based on the experimental test data, a modified model for predicting the dynamic pore water pressure in MICP-reinforced silty sand is proposed. This model is then verified using the test results from this study and also existing literatures. A good agreement between test data and predicted values is obtained, demonstrating the accuracy and applicability of the model. This study provides a reference for the dynamic stability analysis of MICP-reinforced soil and the formulation and optimization of anti-liquefaction soil reinforcement schemes.

To explore the relationship between the volume change characteristics of loess, pore pressure and liquefaction, Gulang Malan loess was selected as the research subject. Unsaturated consolidated undrained tests were conducted to study the shear volume characteristics of loess under different water contents and confining pressures. Saturated consolidated undrained tests were also conducted to examine the stress paths and pore pressure characteristics of loess. Based on these studies, the distribution pattern of the critical state lines under different water contents was analyzed. Critical state lines in saturated conditions were established and compared with those from saturated consolidated undrained tests for validation. This provided a basis for establishing a connection between the loess volume change and pore pressure, leading to the proposal of a liquefaction evaluation method based on unsaturated shear volume. The findings indicate that the stress-strain curves of unsaturated Malan loess generally exhibit strain hardening behavior, with shear deformation being contractive. Conversely, stress-strain curves of saturated Malan loess display strain softening behavior. The deviatoric stress initially increases to a peak value with increasing mean effective stress and then gradually decreases and stabilizes. Critical state lines under unsaturated conditions are approximately parallel. As water content increases, the distribution of the critical state lines shifts downward. Water content has a relatively minor effect on the slope of the critical state line but a significant impact on the intercept. The distance from the initial state of the soil to the saturated critical state line represents the change in pore pressure. The pore pressure calculated based on the saturated critical state line indicates that there is only a possibility of liquefaction in Gulang Malan loess. This research provides valuable exploration in the field of loess liquefaction evaluation.

The concrete lining of underground caverns used for compressed gas energy storage is prone to wide cracks under high internal pressure, which can exceed safety design values and affect the safety of the lining. To address this problem, it is usually necessary to reduce the cross-sectional size, increase the lining reinforcement ratio and reduce the gas storage pressure, which raises construction costs and limits storage capacity. This study adopts a preset crack lining structure that reduces tensile stress by releasing the circumferential displacement of the lining. This structure enhances the resistance of the surrounding rock to the lining, so that the surrounding rock can bear more loads and fully utilize its self-bearing capacity. Relying on actual projects, a two-dimensional numerical model was established with different preset crack depths, positions and numbers. The optimal design scheme for preset crack lining was proposed by analyzing lining damage factor and steel bar stress distribution. The results show that: to effectively release the lining stress, preset cracks must penetrate and sever steel bars. The preset crack lining structure significantly reduces the lining damage and steel bar stress, especially within the 15° range of the cracks. Symmetrical preset cracks prevent the overlap of influence ranges, which can increase far-end steel bar stress. Increasing the number of preset cracks can alleviate lining damage at the joint far ends. However, more preset cracks raise construction costs and complexity while reducing lining quality. Under design requirements, six through symmetrical preset cracks are optimal at a lateral pressure coefficient of 0.39, and four through symmetrical preset cracks are optimal at a lateral pressure coefficient of 1.5.

In view of the problems of broken roof in the end area and severe dynamic manifestation of surrounding rock caused by simultaneous mining of two working faces, this study examines the fracture structure characteristics of thick and hard roof in different layers. It establishes a fracture mechanics model for thick and hard roof, reveals the mechanism of rock burst induced by thick and hard roof breaking in the simultaneous mining working face, and analyzes the evolution characteristics of static and dynamic load stresses in the overlying strata. A collaborative fracturing technique for thick and hard roof working faces and a layered support system with anchor injection reinforcement, known as the “unloading-solidification” collaborative anti impact control technology, are proposed. Research has shown that thick and hard roofs tend to form a seismic source layer for mine impacts, and their fracture energy release has near-far field effects and regional disaster characteristics, leading to different impact dynamics in mines. The energy released by the fracture of thick and hard roof is related to factors including strength, thickness, occurrence layer, overlying rock load, and critical span of the goaf. As the critical span of the goaf increases, the energy released by the fracture of thick and hard roof also increases. The fracture line of the high-level thick and hard roof located on the side near the goaf is a key shock source point for mine induced rockburst. The middle and low thick and hard cantilever beam structure on the goaf side causes the end of the working face to strike 30–40 m and incline 70–80 m, forming a high static load triangular stress concentration area. The superimposed high-level thick and hard roof breaks and is significantly affected by dynamic loads, resulting in crack development on the immediate roof and sub-critical layer 1 roof within 40 m of the end of the working face, increasing the risk of roof collapse accidents. By adopting the collaborative fracturing and anti-impact control technology for upper and lower wells, the high-level shock source layer can be destroyed, the underground middle and low thick and hard cantilever beam can be severed, and the static and dynamic stress response of surrounding rock in the end area can be reduced. Deep and shallow hole grouting solidification and three-stage collaborative anchoring support can form a layered prestressed support shell, improving the strength and integrity of the fractured roof in the end area and enhancing the anti-impact performance of surrounding rock. On-site implementation of the “unloading-solidification” collaborative anti-impact measures results in a 19.2%–20.4% reduction in surrounding rock stress, a 74.0%–77.2% reduction in deformation, a 24.2% reduction in support pressure, decreases dynamic load disturbance on the roof, reduces plastic zone of the surrounding rock, and significantly improves the stability of the surrounding rock in the mining area.

Accurate assessment of the development of soil resistance acting on the pipe during large displacement lateral movement is an important prerequisite for the design of deep-water pipelines. Those pipe-soil interaction problems for light pipes, scraping across the seabed at very shallow depth, have been extensively studied. However, for heavy pipes characterised by diving downwards and getting buried by seabed soil, relevant studies are rather scarce, either in physical or numerical modelling. This scarcity is due to potential instability from extremely sufficient deformation such as soil collapse, as well as high computational cost. This work presents the first systematic numerical analysis of the lateral pipe-soil interaction for heavy pipes in undrained clay using sequential limit analysis (SLA). The evolution of pipe invert trajectory and pipe-soil lateral resistance during lateral movement are examined, and the V-H (pipe weight-lateral soil resistance) yield envelopes at different locations are derived as well, in order to explore the feature of lateral behavior of heavy pipes. It is found that the displacement required by heavy pipes to reach a residual state, characterised by nearly constant lateral soil resistance, is several times greater than that for light pipes. Even after reaching this state, three types of soil failure mechanisms still exist, and the influence of key parameters is analyzed. Finally, a residual resistance assessment model for heavy pipes is proposed, along with a discussion of its applicability.

Characterizing the spatial variability of soil parameters with depth using stationary random fields is challenging, and three-dimensional (3D) slope reliability analysis is often time-consuming. Therefore, the stepwise Karhunen-Loève series decomposition method is employed to generate the stationary random field and the nonstationary random field considering the depth effect (the mean depth of undrained shear strength S_u is different when the random field is realized). A surrogate model based on sliced inverse regression (SIR) and extreme gradient boosting (XGBoost) is proposed, combined with Monte Carlo simulation (MCS) for 3D slope reliability analysis. Take a typical 3D slope, the effectiveness of the proposed method is verified. The calculation results based on stationary and nonstationary random fields are compared, and the influence of the burial depth parameter zb and the trend component b on the 3D slope reliability analysis results is discussed. The results indicate that the surrogate model proposed in this study can accurately and efficiently calculate the 3D slope failure probability. The burial depth parameter zb and trend component b significantly influence the slope reliability analysis results, and these parameter values should be selected reasonably according to the in-situ data. When the slope reliability is analyzed using nonstationary random field theory considering the depth effect, the failure probability increases as the trend component b increases. Conversely, without considering the depth effect, the nonstationary random field yields opposite results. The research results can provide an effective approach for the efficient reliability analysis of actual 3D slope.

To accurately impose inhomogeneous elastic waves in homogeneous media, the domain reduction method (DRM) based on the time-domain perfectly matched layer (PML) was investigated. An improved form of the coordinate stretching function was proposed, along with a method for determining its parameters. The improved perfectly matched layers and the domain reduction method were implemented programmatically based on ABAQUS/Explicit. The time-domain expressions of the free-field displacement for two typical inhomogeneous elastic waves (SV wave incident at supercritical angle and Rayleigh wave) in an elastic half-space were derived. Numerical experiments were conducted to verify the effectiveness of the improved stretching function, the absorption performance of various artificial boundaries for outgoing waves, and the input accuracy of the domain reduction method for SV waves incident at supercritical angles and Rayleigh waves. The results indicate that the improved stretching function has a clear physical meaning and effectively enhances the convenience of parameter selection. Compared to traditional viscoelastic and infinite element boundaries, the perfectly matched layer exhibits higher absorption efficiency for outgoing waves. The domain reduction method program is capable of accurately imposing those two representative inhomogeneous elastic waves, achieving a normalized root-mean-square deviation of less than 1% between the numerical and analytical displacement solutions. The research findings offer valuable insights for studies on seismic resistance and mitigation in underground and geotechnical engineering.

The application of shaped charge blasting in smooth blasting during chamber excavation is investigated. Based on the principle of shaped charge jets, an arc-shaped charge structure is proposed. Numerical modeling of arc-shaped charge blasting (ASCB) is established and compared with cone-shaped charge blasting (CSCB). The findings indicate that ASCB consumes 43.4% less explosive than CSCB, and the efficiency of ASCB in the charge direction surpasses that of CSCB by 25.97%. Upon reaching the blast-hole wall, the shock wave of ASCB is more concentrated than that of CSCB, facilitating the formation of initial cracks in the energy-gathering direction. The pressure exerted by ASCB on the energy-gathering side of the blast-hole wall is 6.26% higher than that of CSCB, whereas the pressure on the non-energy-gathering side is 37.34% lower. The crack length generated by ASCB in the energy-accumulation direction is approximately twice that of CSCB. Consequently, it is concluded that the shaped charge blasting effect of ASCB is superior to that of CSCB. These research outcomes offer a novel approach for directional presplitting blasting.

This study proposes a method to simulate spatially correlated multi-point ground motions, incorporating local site effects using a frequency-dependent equivalent linearization model. The finite element-boundary element coupling method is employed to calculate the nonlinear seismic wave scattering effects in complex sites. Additionally, the amplification effects of ground motions in mountain-valley coupled sites are simulated and analyzed. The results are compared with those obtained from the traditional equivalent linearization method. The frequency-dependent equivalent shear modulus and damping ratio are determined from a standard strain spectrum. The results indicate that the frequency-dependent equivalent linearization method and the conventional equivalent linearization method exhibit similar overall trends. Both reflect significant spatial variations in ground motion within the mountain valley site. Furthermore, compared to linear conditions, both methods show a reduction in the peak ground acceleration and an extension of the predominant period of the response spectrum. However, the frequency-dependent method accounts for the frequency dependence of equivalent shear modulus and damping ratio, effectively improving the high-frequency response estimation that conventional methods often underestimate. Results show that the ground motion accelerations and response spectrum peaks derived from the frequency-dependent approach are markedly higher compared to those from the conventional method, by more than 23%. Additionally, the response spectrum peak shifts toward shorter periods, which better reflects the high-frequency behavior of seismic waves in soil layers. This method can reasonably optimize the high-frequency segment of site response, thereby enhancing the safety of engineering structures.

The internal pore structure and mineral composition of rocks are crucial factors contributing to the instability and failure of rock masses. To investigate the influence of pore structure and mineral composition on crack propagation, a grain based model (GBM) of rock with varying pore structures and mineral compositions was established using the particle flow code (PFC). This study examines the effect of pore size on crack evolution and the propagation behavior of cracks within different minerals. The results indicate that as the short-long axis ratio of pores increases, both the uniaxial compressive strength and elastic modulus of the rock first decrease and then increase, while the degree of rock damage initially increases and subsequently decreases. The most severe failure occurs at the short-long axis ratio of 0.8. With the increase of the short-long axis ratio of pores, the number of internal cracks first decreases, then increases, and finally decreases again. The number of tensile cracks follows a similar trend, whereas the number of shear cracks remains largely unchanged. During the failure process of the rock, intragranular tensile failure is dominant, followed by intergranular tensile failure, while shear failure is relatively rare in both intragranular failure and intergranular failure. Crack propagation behavior in sandstone matrix, clay, and mica is most significantly influenced at the short-long axis ratio of 0.6, whereas the effect on quartz and feldspar is most pronounced at the short-long axis ratio of 0.2. The research results can provide reference and research basis for solving the instability failure problem of rock mass with porosity structures.

Accurate and rapid acquisition of rock strength parameters is essential for ensuring safety in rock engineering. Conventional methods, including cutting and coring, end face polishing, and compression crushing, are time-consuming. This study introduces a continuous rock core scratching technique as a fast and convenient alternative, causing only minor surface scratch. This method allows for the rapid determination of uniaxial compressive strength, internal friction angle and cohesion. To address the limitations of traditional fixed-depth scratching methods that ignore rock core surface roughness, this study introduces a real-time adaptive adjustment technology. This innovation precisely senses surface characteristics and adjusts scratching depth dynamically. Corresponding adaptive continuous scratching equipment has been developed. A series of continuous scratching experiments was conducted on tight sandstone using three modes: fixed depth, adaptive equal division, and adaptive point selection. Results indicate that, compared to standard compression tests, the maximum error in rock strength parameters from the adaptive scratching test was 10.57%. Furthermore, compared to fixed-depth scratching, the accuracy of uniaxial compressive strength testing using adaptive equal division and adaptive point selection scratching improved by 44.44% and 53.09%, respectively. The study also discusses the sources of strength testing errors caused by different scratching modes and clarifies the applicable scenarios for sharp and blunt cutting heads. Core adaptive continuous scratching test technology provides a simple and efficient new method for rapid testing of rock mechanics parameters, optimizing load measurement errors resulting from traditional methods’ inability to ensure constant actual scratching depth.

The study applies the least squares technique in conjunction with a series of spatiotemporally varying pore water pressure measurements to identify the geotechnical parameters of consolidation models. Firstly, a least squares function for pore water pressure, incorporating both temporal and spatial coordinates, is developed. Subsequently, a new Jacobian matrix is constructed to accommodate any number of temporal and spatial measurements. Using Taylor series expansion, the iterative equations for the Gauss-Newton, Levenberg, Marquardt, and Nielsen methods are derived. The proposed methods are validated using two numerical examples. In Case 1, the consolidation coefficient of Terzaghi’s model is identified. Comparative analysis reveals that all four methods converge to the correct solution, although the Marquardt method converges more slowly. In Case 2, the coordinates of a point source in a two-dimensional fluid-saturated medium are identified using a poroelastic consolidation model. The Gauss-Newton method fails to accurately locate the point source, whereas the Nielsen method accelerates convergence but introduces multiple damping coefficient intervals and convergence values. The Marquardt method is more effective for point source identification. Additionally, the study highlights the importance of sensor placement and initial iteration coordinates for accurate point source identification. Both cases show that the proposed methods possess some noise resistance.