Seepage in fractured rock masses is widely encountered in many important engineering fields such as hydropower, civil and transportation infrastructure, energy and mining, and underground disposal repositories. It represents one of the key factors constraining the construction and long-term operation of such projects. As engineering projects advance towards environments characterized by high water heads, great depths, and strong disturbances, conventional models based on linear flow laws have become inadequate for accurately describing seepage behaviors. Nonlinear seepage effects have become increasingly prominent, manifesting as inertial non-Darcian flow at high Reynolds numbers, multiphase nonlinearity in the presence of multiple fluids, coupled nonlinearities arising from interactions among seepage, stress, and chemical processes, as well as boundary- induced nonlinearities under complex boundary conditions. Although significant progress has been made in experimental observation, mechanistic modeling, and numerical methods related to nonlinear seepage, several challenges remain. These include difficulties in conducting in-situ experiments under high-stress and high- pressure conditions, the complexity of quantifying the effects of coupled processes, the empirical nature of model parameter identification, and poor convergence in numerical simulations. Focusing on these theoretical and applied challenges of nonlinear seepage in fractured rock masses, this paper systematically reviews and elaborates on key issues such as the underlying mechanisms, theoretical models, and parameter identification related to non-Darcian flow regimes, multiphase flow effects, coupled processes, and boundary nonlinearities. Furthermore, simulation methods and control techniques for nonlinear seepage in fractured rock masses are introduced. This paper highlights the vital role of nonlinear seepage theory in improving prediction accuracy, enhancing the reliability of safety evaluations, and supporting proactive engineering control. This is demonstrated through engineering applications, including seepage control and assessment in high-pressure water conveyance tunnels, modeling and evaluation of three-dimensional drainage systems in hydropower projects, and long-term performance evolution analysis of seepage control systems. Future research should aim to establish unified theoretical models and highly robust numerical methods, integrate nonlinear seepage analysis throughout the entire engineering design process, and develop intelligent seepage control systems that integrate monitoring, identification, and regulation. By deeply integrating multidisciplinary knowledge with artificial intelligence technologies, a transition from state assessment to proactive control can be achieved.

To investigate the mechanism of fissure expansion in brown coal under high-temperature steam conditions and its regulatory effect on permeability, this study utilizes brown coal from the Huolin River in Inner Mongolia as the research subject. Using a self-developed high-temperature, high-pressure steam convection heating experimental apparatus, the study simulates the in-situ gasification environment of brown coal. Employing a multi-scale, multi-parameter collaborative experimental approach, the research comprehensively utilizes micro-CT three-dimensional reconstruction, scanning electron microscopy (SEM) for microscopic morphology observation, uniaxial compression mechanical testing, and permeability experiments. Quantitative parameters such as fracture volume fraction, average length, and spatial connectivity are used to characterize fracture development, while the thermal deformation coefficient α is employed to characterize the phase transformation characteristics of thermal deformation in the coal body. A fracture propagation evaluation system based on multi-source data is established. The results indicate that: (1) High-temperature steam significantly transforms micro-fractures (100–500 μm) into medium-to-large fractures, with the average length increasing from 305.38 μm to 746.92 μm. (2) The surface of lignite evolves from dense to porous, exhibiting a stepwise fracture development pattern (“initiation-expansion-“Y” type network-overall failure”), accompanied by enhanced permeability. (3) The spatial distribution of fractures demonstrates a “central radiation-edge expansion” characteristic, with 400 ℃ identified as the critical temperature for full fracture network connectivity—porosity increases from 27.1% to 50.2%, and the fracture volume fraction reaches 18.75%. (4) At 400 ℃, thermal deformation undergoes a phase transition: the thermal deformation coefficient α shifts from －1.2% to 0.8%, resulting in the coal body transitioning from contraction to expansion, which elevates permeability by 1.1 times. This research provides theoretical guidance for optimizing seepage channels and process control in in-situ lignite gasification mining.

Fault surface roughness, a critical parameter influencing fault slip behavior, significantly affects fault sliding characteristics through variations in its hierarchy. This study focuses on Jinping marble as the research subject and systematically conducts fault friction tests under the combined effects of varying normal stresses and fault plane roughness (ranging from micrometer to millimeter scale). The aim is to elucidate the influence mechanisms of the synergistic effects of roughness and normal stress on fault sliding behavior characteristics. The main findings are as follows: (1) Fault surfaces with low to moderate roughness are more susceptible to inducing periodic stick-slip oscillations, with the magnitude of shear stress drop positively correlated to normal stress. Low-roughness fault surfaces can counteract the shear strength enhancement caused by roughness variations, thereby dominating the shear strength weakening process. In contrast, high-roughness fault surfaces, due to the dynamic separation effect of asperities, are more likely to trigger single stress drop events. As normal stress increases, local asperities tend to undergo brittle failure, resulting in a sudden decrease in non-periodic stress. (2) The stick-slip behavior of Jinping marble faults can be categorized into four typical modes: regular stick-slip, sub-regular stick-slip, pseudo-chaotic stick-slip, and chaotic stick-slip. Notably, chaotic stick-slip and regular stick-slip exhibit significant differences in periodic characteristics and stress curve morphology. Chaotic stick-slip frequently occurs during the transition phase between stick-slip and stable sliding. (3) The geometric morphology of the fault surface profoundly influences both the mechanical response and the characteristics of the acoustic emission (AE) signals during sliding. The amplitude of local strain reduction diminishes from the shear loading end towards the opposite end. The failure mechanisms of asperities on the fault plane demonstrate hierarchical dependence: frictional wear dominates at low roughness, brittle fracture at high roughness, and a combination of both mechanisms at moderate roughness. Furthermore, the AE signal responses reveal the underlying energy release mechanisms during fault sliding. These research findings provide technical support for the safe development of deep-seated resources.

Under the combined influence of periodic water level fluctuations and the overlying rock mass, the hydro-fluctuation belt of reservoir bank slopes exhibits significant degradation in physical and mechanical properties, particularly in interbedded sandstone and mudstone formations. To investigate the shear mechanical characteristics of sandstone-mudstone interfaces, typical interfaces from the Three Gorges Reservoir area were examined through stress and dry-wet cycle coupling tests. The results indicate that this coupling effect leads to a nonlinear degradation trend in interfacial shear strength, cohesion, and internal friction angle, characterized by an initial rapid decline followed by a gradual reduction. The degradation intensifies with increasing overburden stress. A shear strength degradation model based on the Mohr-Coulomb criterion showed strong agreement with the experimental data. Microscopic analysis revealed a transition in the interface structure from dense to porous, with mudstone degradation playing a dominant role in the weakening of mechanical properties. These findings provide a theoretical basis for the degradation analysis and stability evaluation of clastic rock bank slopes in the Three Gorges Reservoir area.

High-strength mortar is widely employed in the reinforcement of fractured rock masses due to its exceptional strength, durability, and bonding performance. Under dynamic loading, the crack propagation behavior in high-strength mortar–rock composites is complex, with potential for cracks to extend along the interface or penetrate through it. While considerable research has focused on static interfacial fractures, the mechanisms driving penetration propagation under dynamic loading remain relatively underexplored. To address this gap, granite was chosen as the reinforcement target and combined with high-strength mortar to create side-cracked triangular plate (SMCT) specimens. Impact tests were conducted using a modified split Hopkinson pressure bar (SHPB) system. During the tests, an infrared velocimeter measured the impact velocity, while strain gauges and a super-dynamic strain gauge were utilized to collect waveform data. By integrating experimental and numerical methods alongside crack propagation gauges (CPGs), the effects of interface inclination, roughness, and mortar strength on crack propagation parameters, dynamic fracture toughness, and fracture energy were systematically investigated. A numerical model was developed using ABAQUS software, incorporating embedded zero-thickness two-dimensional four-node cohesive elements (COH2D4) to simulate random crack propagation. Crack propagation velocity and time were derived from experimental data, and the dynamic stress intensity factor and dynamic fracture toughness were calculated using a universal function. The results indicate that as the interface inclination increases from 90° to 106°, the average fracture toughness in the mortar and granite regions rises by 19% and 23%, respectively, while the average fracture energy increases by 38% and 56%, respectively. Moreover, when the compressive strength of the mortar increases from 80 MPa to 100 MPa, the average initiation toughness of the specimen improves by 32%. Roughness does not significantly affect penetration crack propagation velocity, dynamic fracture toughness, or fracture energy. Numerical simulations reveal that under impact loading, the tensile stress at the crack tip is significantly greater than the shear stress, which approaches zero, indicating that the SMCT specimens consistently exhibit mode I fracture characteristics.

Quantifying rock strength with randomly distributed fractures is essential for preventing and controlling disasters in underground engineering. This study investigates the incorporation of polyvinyl alcohol (PVA) water-soluble materials in the preparation of rock specimens. The evolution of rock compressive strength in specimens featuring randomly distributed fractures prepared with PVA materials is analyzed, taking into account the influence of confining pressure. Ultimately, a strength model for fractured rock is established by accurately quantifying the damage effects of individual fractures and characterizing the statistical properties of distributed fractures, with its reliability subsequently verified. The results indicate that: (1) Rock specimens with randomly distributed fractures are prepared by mixing PVA water-soluble materials with cement mortar, pouring the mixture, and subjecting the cured specimens to a warm bath treatment. (2) Rock strength exhibits a positive linear relationship with confining pressure and a negative linear relationship with total fracture area. While maintaining a constant total fracture area, rock strength demonstrates a positive linear correlation with the number of fractures. (3) The theoretical strength model successfully reproduces the experimental strength, demonstrating that the established model effectively characterizes the evolution of rock strength under the combined effects of confining pressure and fracture distribution parameters. (4) The sensitivity of rock strength to confining pressure is negatively correlated with total fracture area, while its sensitivity to changes in total fracture area shows a positive correlation with confining pressure.

In studies of fluid flow through single-fractured rock media, the classical geometric percolation threshold loses its validity, and the threshold pressure gradient (TPG), as an empirical parameter describing the onset condition of actual flow, cannot directly provide a basis for the theoretical determination of the percolation threshold. This is because TPG relies on fluid mechanics mechanisms, whereas the percolation threshold is based on network topology statistics. Therefore, it is essential to define a “transport percolation threshold” that characterizes hydraulic critical behavior. Consequently, this study addresses the determination of the inflection point in Darcy-non-Darcy flow through rough fractures and investigates the transport percolation threshold in seepage flow, focusing on the discontinuous relationship between pressure gradient and flow velocity during transitions from low to high velocities. A comprehensive Bingham fluid seepage model, incorporating fractal dimensions of fracture tortuosity and aperture, is developed. By integrating unit percolation models with diffusion equations, a global percolation model is established, allowing for numerical solutions for full-field percolation in rough fractures. The results indicate that, compared to the assumptions of Darcy flow, the unit percolation model under the Forchheimer flow assumption—characterized by its unique inertial term—more accurately captures the influence of geometric percolation parameters (such as roughness angles and hydraulic aperture) on fluid flow paths during the percolation stage. During phase transitions in percolation, the outlet flow velocity conforms more closely to the nonlinear characteristics described by Forchheimer′s equation rather than Darcy′s linear assumption. This understanding offers a novel perspective for investigating the mechanisms of low-velocity non-Darcian flow.

The stress-pore-seepage coupling mechanism in sandstone aquifers affected by mining disturbances is crucial for safeguarding roof aquifers and predicting contaminant transport during coordinated coal and uranium mining operations. This study employs nano-CT scanning, nuclear magnetic resonance (NMR) data calibration, and three-dimensional model reconstruction to perform fluid-solid coupling numerical simulations at the microscale within sandstone. Based on pore size distribution, the NMR T2 spectrum can be broadly categorized into four segments: pores smaller than 1 nm, pores between 1 nm and 1 ?m, pores between 1 ?m and 6 ?m, and pores larger than 6 ?m. The NMR T2 spectrum exhibits two peaks at pore sizes of 1 nm–1 ?m and above 6 ?m. NMR results during seepage indicate that, under an external load of 2 MPa and an increase in water pressure from 0 MPa to 0.5 MPa, nanopore (1 nm to 1 ?m) porosity decreases from 5.06% to 4.65%, while micropore (＞1 ?m) porosity increases from 0.14% to 0.6%. As external stress continues to rise, both nanopore and micropore porosity decrease linearly: nanopores decline from 4.65% to 4.24% (a reduction of approximately 8.82%), and micropores decrease from 0.6% to 0.46% (a reduction of approximately 23.3%). The proportion of total porosity remains largely unchanged, with nanopores accounting for about 90% and micropores comprising approximately 10%. A sandstone pore reconstruction method was developed utilizing NMR and nano-CT data, with a minimum representative element size of 100 pixels. Microscopic simulations reveal that increasing external stress leads to complex stress concentration and attenuation near pores. During seepage, flow lines converge toward pore regions and preferentially traverse zones with lower effective stress. Furthermore, reverse flow and boundary layer effects occur internally during seepage, intensifying under increasing stress.

To address rib spalling and roof falls triggered by strong deep mining-induced disturbances, which limit the safe and efficient extraction of deep coal resources, we employed an in-house developed microcomputer-controlled electrohydraulic servo testing system for coal and rock, capable of combined static and dynamic loading with adaptive coupling. Three coupled loading paths were implemented: unloading of confining pressure (SX group), unloading under dynamic disturbance with a variable lower stress limit (BX group), and unloading under dynamic disturbance with a constant lower stress limit (HX group). We characterized the effects of low-frequency dynamic disturbance on the mechanical response and failure modes of coal during the unloading process. The results indicate that: (1) For SX group specimens, peak strain and peak stress positively correlate with confining pressure. After experiencing low-frequency dynamic disturbance, BX and HX group specimens exhibited reduced peak strain, with peak stress decreasing by 4.553% to 8.432% and 0.475% to 6.322%, respectively. Stress-volumetric-strain curves demonstrate dilatancy between 0 and 20 MPa, which initiates before the peak, followed by a compaction mechanism between 30 and 50 MPa. This transition is governed by confining pressure and remains independent of the stress path. (2) The deformation modulus experiences a three-stage evolution during unloading: a logarithmic decline, followed by linear attenuation, and finally an abrupt drop to failure. The instantaneous decay rate follows a U-shaped trajectory. When confining pressure is at or below 30 MPa, the rate of modulus degradation is highly sensitive to unloading. Under confining pressures of 40–50 MPa, low-frequency dynamic disturbances induce a sharp decline in modulus values into negative territory, followed by a rapid rebound. During unloading, the coal sample exhibits a damage mechanism characterized by transient strengthening and progressive deterioration. (3) Macroscopic failure modes are influenced by the level of confining pressure and the stress path. As confining pressure increases, SX group specimens transition from single shear to multiple shear failure, accompanied by a progressive reduction in surface tensile cracks. BX group specimens evolve from multiple shear failure to a combined multiple shear and transverse shear failure, characterized by lamellar scaly tensile and shear composite fragmentation. HX group specimens display multiple shear failure; however, at 30–50 MPa, they also exhibit significant tensile fragmentation and particle-scale pulverization. (4) Compared to SX group specimens, BX and HX group specimens show larger fluctuations in modulus values, with abrupt changes in modulus concentrated during disturbance stages I to II and III to IV, respectively. Based on analyses of acoustic emission RA and AF values, tensile cracking predominates in SX specimens. Along the BX group path, the fraction of tensile cracks increases progressively during confining pressure unloading and the early disturbance stage. Under HX group conditions，at stages III to IV, the proportions of tensile and shear cracks surge simultaneously.

 To address the significant weakening of deep surrounding rock under coupled hydro-thermal-mechanical (HTM) conditions, conventional triaxial compression-permeability tests were conducted on sandstone specimens immersed in water at varying temperatures using a triaxial multi-field coupling apparatus. The main findings are as follows: (1) The HTM coupling effect markedly weakens the pre-peak load-bearing capacity of rock; elevated temperature intensifies the initial damage and the dissolution of internal cement, resulting in damage stress , peak strength and residual strength  decreasing significantly with increasing water temperature. (2) During the unstable crack-propagation stage, permeability (K) exhibits a quasi-exponential increase, with a faster growth rate at higher temperatures; post-peak, the dissipated energy Ud rises sharply and is expended on rock dilatancy and macroscopic cracking, driving K rapidly to its peak—an overall “∧” -shaped trend—where the strain corresponding to the intersection of elastic energy  and  can serve as a characteristic threshold for the surge of K to its maximum. (3) Approximately 55 ℃ is identified as a critical temperature threshold for the transformation of the mechanical response mechanism of sandstone; above this temperature, the mechanism shifts from water-rock physical softening to a composite damage mode dominated by mineral dissolution and thermally induced microcrack propagation, with the dilatancy angle? and K increasing significantly, and the peak permeability value of 85C–15 sample is about 1.54 times that of 25C–15 sample. (4) Dry and low-temperature water-soaked specimens are characterized by throughgoing, high-angle shear planes, exhibiting typical brittleness, while high-temperature water-soaked and high-initial-damage specimens display enhanced local plasticity and dilatancy, forming conical, non-throughgoing structures with earlier post-peak instability. These results reveal the weakening mechanism of sandstone under high-temperature water immersion and provide a foundation for evaluating the long-term stability of underground projects, such as deep, high-temperature mines and deeply buried, water-rich tunnels.

The magnitude of earth pressure is closely related to the deformation state of retaining walls. To describe the progressive shear failure characteristics of soil behind the wall under passive conditions, a novel analytical method for calculating passive earth pressure considering wall deformation is proposed. Based on Coulomb earth pressure theory and the hyperbolic mechanical model, the concepts of point deformation failure rate and area (length) deformation failure rate are introduced to quantify the stress states along the rupture surface. A static equilibrium model of a wedge body is established, and an analytical solution for passive earth pressure under non-limit conditions is derived. The results show that passive earth pressure increases nonlinearly with wall deformation, with the most significant pressure increments occurring in the upper one-third and middle regions of the wall height. An increase in the wall-soil friction angle δ leads to a decrease in the rupture angle and a more nonlinear distribution of earth pressure. The proposed method shows good agreement with Coulomb theory and experimental results, verifying its accuracy and engineering applicability. This method provides a new theoretical framework for evaluating passive earth pressure in deformable retaining structures.

The seismic dynamic response of subsea tunnels in complex hydrogeological environments is crucial for ensuring their safe operation. This study investigates the combined effects of soil-structure interaction (SSI), cover-to-diameter ratio (C/D), and hydrostatic-hydrodynamic pressures on tunnel lining responses, using the Shantou Bay Tunnel as a case study. The Davidenkov constitutive model is employed to characterize the nonlinear dynamic behavior of marine soils, while the coupled acoustic-structure method is integrated into the finite element model to capture the interaction between seawater, seabed, and structure. Results indicate that, under 0.2 g seismic excitation at a water depth of 50 m, the peak tunnel diameter deformation ratio with SSI is 23.74% greater than that without SSI. As the depth increases, the combined hydrostatic and hydrodynamic pressures amplify the deformation ratio by 6% to 42% compared to hydrostatic pressure alone, suggesting that neglecting hydrodynamic effects at significant depths would substantially underestimate structural deformation. Furthermore, when the tunnel C/D is 1.5, the additional impact of hydrodynamic pressure is only 9% to 14%, which is considerably lower than the 22% to 66% observed for a C/D of 0.9. Additionally, the hydrodynamic pressure on the seabed exhibits a non-uniform “double-peak and single-trough” distribution due to the presence of the tunnel.

Sediment-type salt cavern storage facilities are critical components of energy infrastructure that utilize the space within sediment voids to store gas. This is accomplished by injecting high-pressure natural gas or air into salt cavities, which displaces brine from the sediment voids. During the gas injection and brine displacement processes, the high-velocity flow of brine in low-level debrining wells carries sediment particles, leading to sand blockages that adversely affect brine expulsion efficiency. The forces acting on spherical particles during fall and horizontal movement were analyzed, resulting in the derivation of the terminal settling velocity formula for particles in free fall. Additionally, a terminal settling velocity formula that considers the morphologies of sediment particles and the sand concentration in brine was developed. Under identical conditions, brine with a higher sand concentration exhibits a greater capacity to carry sand. When the geometric mean diameter is constant, flatter-shaped particles are more readily transported by brine. Using a CFD-EDEM coupled simulation method, the distribution of the solid-liquid two-phase flow field in debrining wells was simulated over time, accounting for varying brine flow rates and sediment accumulation depths. When discharging brine at low flow rates, it is essential to promptly clear the debrining channel to prevent sediment accumulation at bends. The layering effect of brine flow rates results in particles in the lower section of the debrining channel accumulating more easily. At the same inlet flow rate, an increase in particle accumulation depth enhances the sand-carrying capacity of the brine. An analysis of the particle size distribution of returned sediment particles during the gas injection and brine displacement process in a specific salt cavern revealed a particle size range of 0.075 to 40 mm, which was consistent with the results obtained from simulation modeling. The primary sources of error and their corresponding solutions were also identified. The research findings provide valuable guidance for improving brine displacement efficiency and preventing sand entrainment and blockages in debrining wells associated with salt cavern void injection and brine displacement projects involving sediment-type salt caverns.

The parallel testing of the High Gravity Technology Shaker (Higee shaker) is a crucial method for evaluating the effectiveness of geotechnical seismic calculation and analysis techniques, as well as for advancing test technology. This study addresses the widespread controversy regarding the reliability of test technology due to the discrepancies observed in international parallel test results. It elaborates on the key technologies of the DCIEM-40 Higee shaker, including load control, model preparation, data measurement, and other testing procedures. By modifying two sets of parallel tests under a single variable, this research explores the consistency and comparability of results obtained under different conditions, thereby verifying the feasibility of conducting parallel tests and the reliability of the associated key technologies. The findings indicate that: (1) The constant-amplitude sine sweep motion exhibits continuous frequency and uniform amplitude characteristics compared to white noise waves, making it more effective for identifying the quality and self-oscillation cycles of the test model. The compression seismic waves generated with varying centrifugal accelerations and amplitudes yield nearly identical prototype waveforms, with an average peak deviation of at most 2.99% and a maximum error in the spectral area of 9.86%. (2) The values of the excess pore water pressure ratio at different horizontal positions at the same depth, as well as the excellence cycle of the site, are generally consistent with the theoretical values within the same model. The measured periods closely align with the theoretical values, and the dynamic responses of the excess pore water pressure ratio and acceleration at different depths exhibit strong correlation in both amplitude and phase, confirming the accuracy of model preparation and static dynamic measurements. (3) In parallel tests, the acceleration, excess pore water pressure ratio, displacement, and recordings at the same locations across different models show considerable agreement, further substantiating the stability and repeatability of the model preparation and experimental measurement techniques. Additionally, the multi-physical seismic responses of various soils and structures under the influence of a single variable demonstrate significant differences, thereby validating the comparability and feasibility of the parallel tests. The results of this research provide valuable insights for the operation of existing Higee shakers, the development of new equipment, and the standardization and normalization of test technology in China.

To accurately predict the collapse step distance of mudstone interlayers during cavern leaching and ensure the stability of salt cavern gas storage facilities, this study conducts an in-depth analysis of the structural characteristics and mechanical properties of mudstone interlayers, establishing a predictive model for interlayer fracture. Macroscopic analysis and point load tests on mudstone interlayer samples from Submember 3b of Member 3 of the Buxin Formation in the Sanshui District salt mine revealed the following: (1) the structural characteristics of the mudstone interlayer vary significantly from top to bottom, with the lower section developing multi-angle fractures (partially filled with salt rock), while the upper part remains dense; (2) consequently, the interlayer is categorized into an upper high-strength mudstone and a lower low-strength mudstone, with point load tests confirming that the uniaxial compressive strength of the high-strength mudstone is approximately 5.5 times that of the low-strength mudstone; (3) under brine soaking, the high-strength mudstone exhibits significant softening effects within the initial 14 days, after which its strength tends to stabilize; the long-term strength is primarily influenced by intrinsic interlayer characteristics, such as the proportion of high-strength mudstone and interlayer thickness. Based on these properties, the progressive fracture mechanism of the mudstone interlayer is revealed, which can be divided into three stages: low-strength mudstone fracture, high-strength mudstone fracture, and operational-stage fracture. Ultimately, a fracture distance prediction formula is established that comprehensively considers soaking time and interlayer characteristics (high-strength mudstone proportion and thickness). The study clarifies that: (1) buckling failure occurs in the interlayer when the high-strength mudstone proportion exceeds a critical value (approximately 0.2); (2) when the high-strength mudstone proportion is relatively low, non-buckling failure is more likely to occur. These research findings provide a theoretical basis for predicting and controlling interlayer collapse during the leaching of salt cavern gas storage facilities.

To investigate the differences in spatially axisymmetric earth pressure of a foundation pit within unsaturated soils under various transient suction conditions, two representative transient suction methods were selected for comparative analysis. These methods were evaluated for their similarities, differences, and variations in suction behavior. The differential slip line equation and a transient iterative solution for the earth pressure surrounding a spatially axisymmetric circular foundation pit in unsaturated soils were formulated. The validity of the proposed solution was confirmed by comparing it with existing earth pressure solutions reported in the literature. Subsequently, parametric studies were conducted to examine the effects of these two transient suction methods on earth pressure in different soil types—sands, silts, and clays. The results indicate that the proposed transient iterative solution for spatially axisymmetric earth pressure is not limited to any specific transient suction method and can accommodate variations in rainfall intensity, duration, and soil unit weight, thereby offering better alignment with real-world engineering scenarios. During rainfall, both transient suction methods exhibit consistent performance regarding the magnitude and profile of matric suction as well as the earth pressure of foundation pits. As initial rainfall intensity increases, matric suction decreases while earth pressure increases. However, each method has its own scope of application; misapplication of a transient suction method may lead to an overestimation of earth pressure. For sands, the earth pressure of foundation pits is only slightly affected by rainfall intensity or duration. In contrast, for silts and clays, earth pressure significantly increases during rainfall with the rise in both rainfall intensity and duration. After rainfall ceases, earth pressure initially rises and then declines over time, which can be attributed to the gradual increase in matric suction caused by evaporation, exhibiting a certain time delay.

Soil erosion is a global environmental issue that can trigger disasters. This study evaluated the effectiveness of alkali-activated binder (AAB) treatment on the performance of natural geotextiles (coir mats and straw mats) in controlling slope erosion through field-based artificial rainfall experiments. The results demonstrated that AAB treatment significantly improved the microstructure and mechanical properties of the geotextiles. The tensile strength of AAB-treated coir mats increased by 20%, with an elongation at break of 54.6%. Under a rainfall intensity of 120 mm/h and a slope gradient of 1:1, AAB-treated coir mats reduced the peak runoff rate by 70% and the peak erosion rate by 8.8% compared to bare slopes. High-intensity rainfall drives rapid yet spatially heterogeneous water movement. While the 1:1.75 gradient enhances infiltration depth and soil moisture uniformity, the 1:1 slope induces surface runoff, resulting in maximum water accumulation at the slope base. Alkali-activation reactions in AAB-functionalized geosynthetics produce cementitious phases that refine pore networks, increasing the stabilized water content of slope soils by 10% to 15%. These microstructural modifications concurrently enhance moisture retention capacity and erosion resistance in vegetated slope systems.

The mechanical behavior of the granite residual soil-concrete interface is critical to the overall stability and safety of geotechnical structures. To investigate the effects of shear amplitude and shear frequency on the cyclic shear characteristics of granite residual soil-concrete interfaces, a series of large-scale horizontal cyclic direct shear tests were conducted, varying shear amplitudes (1, 3, 6 and 9 mm) and shear frequencies (0.1, 0.5, 1 and 2 Hz). Key parameters, including shear stress-displacement response, maximum shear stress, and vertical displacement, were analyzed. The results indicate that maximum shear stress increases with shear amplitude, although the growth rate gradually decreases. Significant changes in vertical displacement primarily occur within the first 20 cycles, after which it stabilizes, reflecting the particle rearrangement effects during the initial cycles. Shear stiffness decreases at higher shear amplitudes, while the damping ratio exhibits a fluctuating trend, suggesting that the energy dissipation mechanism of the soil is influenced by shear amplitude. Numerical simulations further reveal that, as the number of cycles increases, the number of force chains within the soil also rises, with most force chains consisting of three particles. The principal directions of normal and tangential contact forces are closely related to the shear direction, with the principal direction deflecting approximately 35° in response to changes in shear direction.

To investigate the characteristics and mechanisms of gas migration and to predict the effective gas permeability in saturated bentonite within deep geological repositories, water saturation, gas injection, and mercury intrusion porosimetry (MIP) tests were conducted on GMZ bentonite specimens under a confining pressure of 8 MPa, taking temperature effects into account. The results indicate that the intrinsic permeability measured with water increases as temperature rises. During the gas injection test, the gas pressure recorded downstream exhibits a three-stage evolution process. Gas displaces pore water and induces pore shrinkage in the specimen, with the shrinkage ratio varying with temperature. As the gas injection pressure increases, mechanical gas breakthrough may ultimately be triggered by pore expansion. At the same injection pressure, effective gas permeability increases with rising temperature. A prediction model for effective gas permeability was developed based on the water-measured intrinsic permeability and the Hagen-Poiseuille model, validated by considering the influences of temperature, the Klinkenberg effect, and gas injection pressure.

 Clogging phenomena have been observed during the consolidation of dredged slurry treated with prefabricated horizontal drains (PHDs) in conjunction with vacuum preloading (VP). Previous studies indicate that the clogged zone exhibits an elliptical shape, with its extent gradually expanding over time. This study proposes a nonlinear consolidation model for PHDs-VP-treated dredged slurry, incorporating the development of the elliptical clogged zone surrounding the PHDs. The governing equations are established, and numerical solutions are derived using the finite element method. The accuracy and applicability of the model are validated through degradation analysis and comparisons with experimental results. Subsequently, a parametric analysis is conducted to assess the influence of key factors on consolidation, including the clogging effect, PHD layout ratio, slurry layer thickness, and soil nonlinear characteristics. The results demonstrate that the clogging effect significantly slows the consolidation rate, with the impact becoming more pronounced as the severity of clogging increases and the clogged zone develops more rapidly. Increasing the PHD layout ratio or reducing the slurry layer thickness effectively accelerates consolidation. However, once the layout ratio surpasses a critical threshold, further increases yield only marginal effects. Additionally, the optimal layout ratio decreases with increasing slurry layer thickness, and relevant engineering recommendations are provided. Furthermore, the consolidation rate decreases with a higher compression index but increases with a higher permeability index.