Underground lined gas storage reservoirs for compressed air energy storage (CAES) are subjected to expanding internal pressure, which often results in cracking in the lining and yielding in the surrounding rock. However, research on the cracking and yielding characteristics of lined reservoirs remains relatively insufficient. Drawing upon the multi-layer thick-walled cylinder theory and considering the stratification and equivalence of steel lining, concrete, steel reinforcement, and surrounding rock, this study simplifies cracked concrete as an orthotropic layer and models the surrounding rock using the Mohr-Coulomb yield criterion and non-associated flow rule. Analytical solutions for stress and displacement during the stages of elastic deformation, brittle cracking, and plastic yielding are derived accordingly. Furthermore, by integrating the improved Dong Zheren crack calculation method, the numerical solution for the radial displacement of the lining’s outer wall is employed to replace the traditional shell approximation, facilitating the simultaneous prediction of the maximum crack width in the lining and the radius of the plastic zone in the surrounding rock. Additionally, this study analyzes the influence of factors such as storage reservoir radius, internal pressure, steel lining thickness, concrete strength grade, and thickness on the cracking behavior of the lining and the yielding characteristics of the surrounding rock. Finally, an in-depth discussion is conducted on the cracking behavior of the lining and the yielding characteristics of the surrounding rock. Results indicate that within the typical engineering parameter range defined in this study, the internal pressure of the storage reservoir, the quality grade of the surrounding rock, and the in-situ stress are the primary factors affecting the cracking width of the lining, while the in-situ stress is the main factor influencing the cracking and yielding ranges. The lining rapidly cracks and fails when internal pressure exceeds a certain threshold. The cracking and yielding ranges primarily occur between 0 and 10 meters and gradually increase with rising gas storage pressure. The findings provide theoretical support for analyzing the cracking and yielding characteristics of underground lined storage reservoir structures.

Based on the Hoek-Brown strength criterion, this study develops a semi analytical approach for calculating the stress and displacement of surrounding rock throughout the excavation and high-pressure operation stages of a compressed gas energy storage cavern, thereby elucidating the evolution patterns of the stress path and failure mode in the surrounding rock. The findings reveal that the geological parameters exert minimal influence on the distribution of radial stresses within the surrounding rock, and significantly affect the distribution of circumferential stresses. Poorer geological conditions lead to a larger circumferential stress and a wider plastic zone. For medium-soft rock formations (e.g. geological strength index GSI = 35), the Mohr-Coulomb strength criterion may overestimate the bearing capacity of surrounding rock during high-pressure air storage stage. Should the surrounding rock transition into a plastic state during cavern excavation, it will be subjected to both radial and circumferential compression under conditions of high internal gas pressure. As the internal gas pressure escalates, the stress state of the surrounding rock sequentially progresses through plastic unloading, plastic loading, and plastic expansion stages. Notably, the critical internal pressure threshold during the plastic expansion stage is roughly twice the initial in-situ stress. Once the internal gas pressure reaches this critical pressure, the radius of the plastic zone in the surrounding rock expands almost linearly with the internal pressure, resulting in a swift enlargement of the plastic zone and a nonlinear surge in the displacement of the surrounding rock. Consequently, under unfavorable geological conditions, it is inadvisable to indiscriminately elevate the maximum gas storage pressure within the cavern.

Compressed air energy storage (CAES) is a key technology for the consumption of renewable energy and peak shaving of power grid. Artificial cavern gas storage has promising application prospects because it is less constrained by site selection and offers better controllability of construction quality. However, the lining and surrounding rock are subjected to significant tensile stress during high-pressure operation. When the maximum tensile stress exceeds the material’s critical strength, tensile failure occurs. To address this issue, the reinforcement ratio of the lining must usually be increased, or the chamber size and storage pressure must be reduced. However, these measures increase construction costs and limit storage capacity. In this study, an optimized structure is proposed in which the lining is placed inside the sealing layer. From the inside outward, the structure consists of the lining, sealing layer, leveling layer, initial support, and surrounding rock. Numerical simulations and analyses are conducted based on a thermo-mechanical coupling model. The results show that the sealing layer temperature in the optimized structure is significantly lower than that in the traditional structure because of the protective effect of the lining. When using steel plate as the sealing material, the maximum temperature is reduced by 46.08%. In terms of stress, the entire lining structure is subjected to circumferential tension and radial compression. After structural optimization, the maximum tensile stresses in the sealing layer, concrete lining, and surrounding rock are reduced by 16.00%, 28.19%, and 24.73%, respectively. Furthermore, the load-sharing results show that more than 70% of the pressure is borne by the surrounding rock in both structures. In terms of deformation, the maximum displacement occurs at the top of the lining. The overall displacement variation of the optimized structure is relatively small. Further analysis examines the lining structure’s mechanical response under high, medium, and low in situ stress levels. Compared with the traditional structure, the optimized structure reduces the sealing layer’s maximum first principal stress by 40.26%, 32.01%, and 22.46% under high, medium, and low in situ stress levels, respectively. This reduction demonstrates the optimized structure’s effectiveness in mitigating circumferential tensile stress in the sealing layer. Surrounding rock grade and deformation modulus significantly influence the structure’s mechanical response. For gas storage sites, surrounding rock of Grade III or higher is selected. Moreover, the mechanical properties of four kinds of sealing layer materials are compared. The steel plate and fiber-reinforced plastic (FRP) are subjected to circumferential tension and radial compression, whereas flexible concrete and rubber are in compression. Steel plate is recommended for traditional structure, whereas flexible concrete is recommended as the sealing material for optimized structure, because it minimizes stress and deformation in the surrounding rock. In summary, for artificial cavern gas storage, the optimized structure proposed in this study is more conducive to structural stability than the traditional structure. The findings provide valuable guidance for the design of artificial cavern lining structures in compressed air energy storage applications.

The design of steel plate thickness holds substantial significance in the context of the sealing layer design for compressed air energy storage (CAES) artificial caverns. To ascertain the relationship between the steel plate thickness and factors such as the cavern diameter, surrounding rock modulus, and internal gas storage pressure, a numerical simulation method was used to analyze the stress characteristics of the steel plate under the influence of these aforementioned factors. Furthermore, a theoretical analysis method was adopted to examine the critical buckling thickness of the steel plate under external water pressure and the corrosion thickness of the steel plate under the operating environmental conditions of the CAES artificial caverns. Ultimately, considering the influencing factors such as stress deformation, buckling characteristics, and corrosion rate of the sealing steel plate, a method for determining the thickness of the sealing steel plate was proposed. The research results show that the fitted empirical formula, which establishes the relationship between gas storage pressure and steel plate thickness, exhibits minimal error when calculating critical pressure or critical thickness. Specifically, the error calculated by stress control is a mere 2.37%, while that calculated by strain control is only 2.35%. The critical thickness of steel plate without stiffening ring presents a nonlinear increasing trend as external pressure rises, whereas the critical thickness of steel plate with stiffening ring exhibits a linear increasing trend with the augmentation of external pressure. In the environment characterized by high temperature and high humidity, the surface of steel plate undergoes overall uneven corrosion, with severe localized corrosion. Consequently, the thickness of steel lining should be increased accordingly. Finally, the method proposed in this paper for determining the critical thickness of the steel lining demonstrates favorable applicability under the research conditions delineated herein, thereby offering valuable insights for the design of steel plate sealing strategies.

A series of undrained cyclic triaxial tests were conducted on calcareous sand from the South China Sea, Fujian silica sand, and Nanjing fine sand. The liquefaction flow characteristics and evolution mechanism of soil state of saturated sand under different influencing factors were studied based on the proposed tension and compression apparent viscosity η_ct  . The main conclusions are summarized as follows: (1) Considering that the hysteresis loop of shear stress-strain rate of saturated sand during cyclic loading is asymmetric during the extension and compression stages, a definition of η_ct / η_o that accounts for the disparity in fluidity during these two stages is proposed to assess the liquefaction flow characteristics of sand. (2) The relationship between normalized apparent viscosity ratio (η_ct / η_o , where η_o is the η_ct -value of the first cycle) and the excess pore ratio (r_u) is found to be independent of relative density (D_r), loading frequency (f), cyclic stress ratio (CSR) and consolidation confining pressure ( σ'_c). It is initially identified that the unique development mode between η_ct / η_o and double-amplitude shear strain (γ_DA) remains unaffected by variations in sand type, the initial soil state, and loading conditions. (3) Both flowability difference parameter λ and the tension and compression apparent viscosity gradient Δη_ct / η_ct  initially increase and subsequently decrease as r_u increases, and the r_u corresponding to the peak value of these two are essentially identical, and can be regarded as the initial liquefaction point of soil. A method is proposed for distinguishing the physical states of sandy soil during liquefaction into solid, solid-liquid, and fluid stages.

The utilization of excavated soil and fly ash to produce foamed lightweight soil (FLS-FE), and its application in subgrade filling in soft soil areas or the control of uneven settlement at the transition zones between strong and weak subgrades, are a green, environmentally friendly, and effective treatment solution. Guided by concept, a series of laboratory tests were conducted to investigate the variation patterns in fluidity, water absorption, and unconfined compressive strength of FLS-FE at different mixing ratios. Further wet-dry cycling and freeze-thaw cycling experiments were implemented to reveal the evolution patterns of FLS-FE under long-term service conditions. The test results indicate that the fluidity of FLS-FE is significantly influenced by the content of excavated soil and fly ash, while fly ash and hydrated lime can reduce its water absorption. The dry density correlates with compressive strength changes. As the excavated soil content increases, the compressive strength of FLS-FE decreases significantly. However, the incorporation of both fly ash and hydrated lime can effectively enhance its strength and toughness. In particular, adding 4% hydrated lime for alkali activation to stimulate the reactivity of the solid waste molecules can increase the compressive strength by 43.9%.In terms of durability, when incorporating excavated soil alone at ≤50% dosage, the strength loss after 20 cycles does not exceed 30%. At a 60% dosage, the strength loss of FLS-FE reaches 46% under wet-dry cycling and 40% under freeze-thaw cycling. However, The addition of fly ash can notably mitigate this strength degradation. After introducing hydrated lime to create an alkaline environment, the mass loss of FLS-FE remains below 13% after wet-dry cycles and below 12% after freeze-thaw cycles, with durability coefficients consistently exceeding 70%. Based on the experimental findings, it is recommended that the content of excavated soil in FLS-FE for subgrade filling should not exceed 50%; the overall solid waste utilization rate can reach 60% by incorporating fly ash, and adding 4% hydrated lime can maximize the performance enhancement of FLS-FE.

This study investigates the mechanical properties and microstructural evolution of peaty soils under freeze-thaw (F-T) cycles through unconsolidated undrained (UU) triaxial shear tests and scanning electron microscopy (SEM). The effects of F-T cycles (0−30), confining pressure (100−400 kPa) and fiber content (0%−12%) were systematically evaluated. Results indicate that the ultimate strength and shear strength decrease as the number of freeze-thaw cycles increases, with the most pronounced reduction occurring during the first 5 cycles. Beyond 15 cycles, the rate of decrease diminishes, and the curves tend to flatten. The fiber reinforcement significantly mitigates the strength degradation caused by freeze-thaw cycles. The most significant improvement is observed at a fiber content of 12%. The fibers act as bridging elements that improve soil particle connectivity, thereby strengthening cohesion and mitigating particle displacement and deformation during freeze-thaw processes. SEM analysis reveals that fiber-soil interaction mechanism undergoes a progressive transformation with increasing fiber content, evolving from localized fiber embedding to comprehensive network formation through fiber entanglement. This structural evolution establishes robust inter-aggregate connections that enhance the soil matrix integrity. Following 30 freeze-thaw cycles, no apparently penetrating fissure was formed although the freeze-thaw process damaged the connection between fibers and soil aggregates, demonstrating the effectiveness of fiber reinforcement in mitigating freeze-thaw damage. These findings provide critical insights into the microstructure-mechanical properties relationships of peaty soils, offering practical guidance for foundation treatment in seasonal frozen peat regions and controlling the engineering diseases problems.

Rock breaking by disc cutter is a fundamental mechanical behavior in tunnel boring machine (TBM) tunnelling. Scholars have conducted extensive studies on rock-breaking theories, but systematic comparisons between the theoretical tunnelling parameters and experimental results are rarely reported. This study presents theoretical and experimental studies on TBM disc cutter rock breaking. First, three types of theoretical models, i.e., compressive rock breaking, compressive-shear rock breaking, and compressive-tensile rock breaking, are reviewed, and the expressions for normal force and rolling force in seven classical calculation models (Evans, Roxborough, Wijk, SJTU, CSM, Sanio, and NEU models) are summarized. Leveraging a self-developed TBM tunneling comprehensive test platform, laboratory tunnelling tests were conducted on low-, medium-, and high-strength sandstones, with key parameters such as cutterhead thrust, torque, and displacement obtained. By comparing theoretical calculations with experimental results, it was found that the CSM model performed best in both thrust and torque calculations, with deviations controlled within 26%, making it the preferred model. The Evans and NEU models generally yielded lower values than experimental results and were suitable for preliminary estimations, making them the second-best recommended models. The Roxborough, Wijk, SJTU, and Sanio models exhibited deviations exceeding 100%, necessitating adjustments in accordance with specific engineering conditions, thereby rendering them as alternative models. This study reveals the influence of rock strength on model applicability, providing theoretical references for TBM tunnelling parameter prediction and rock-breaking mechanism research.

The integrated physicochemical approach, which combines flocculation, solidification, and vacuum preloading, presents an efficient strategy for the resource utilization of slurry-like mud. To address the limited understanding of the development of unconfined compressive strength (UCS) in treated slurry-like mud, this study systematically conducted unconfined compressive strength tests. The investigation primarily focused on examining the influence of curing age, preloading stress, equivalent initial water content, and binder dosage on the strength characteristics during the early to medium stages. The test results unveiled distinct relationships: UCS exhibits rapid growth during the initial curing stages, followed by a gradual deceleration in the growth rate. Elevated preloading stress induces a nearly linear increase in strength, whereas an increased binder dosage significantly enhances UCS. Conversely, a higher equivalent initial water content diminishes the strength. Based on a rigorous analysis and fitting of the experimental data, this research developed a novel hyperbolic strength development model. This model uniquely incorporates the effects of curing age, preloading stress, equivalent initial water content, and binder dosage as key governing parameters. The comprehensive model offers a valuable theoretical framework for predicting the strength behavior of modified fluid mud treated by this physicochemical composite method in practical engineering applications.

In practical engineering, the rock mass in the hydro-fluctuation zone of the bank slope is not only subjected to wet-dry cycles, but also influenced by overlying stress, especially clastic rocks represented by mudstone. To study the shear mechanical deterioration characteristics of mudstone in the hydro-fluctuation zone under the combined action of stress and dry-wet cycles, typical mudstone from the bank fluctuation zone of the Three Gorges Reservoir Area was selected as the focal point of this study, and water-rock interaction tests considering the combined action of overlying stress and dry-wet cycles were carried out. The findings revealed: (1) During the combined action of stress and dry-wet cycles, the overlying stress accelerated the deterioration of the shear mechanical properties of mudstone. The greater the overlying stress, the more obvious the decline of the shear stress-shear displacement curve and the steeper the decrease in its slope, and the lower the shear strength and residual strength. (2) The shear strength of mudstone demonstrated a degradation pattern characterized by an initial rapid decline, followed by a gradual slowdown, and ultimately stabilization. The degradation observed in the first five cycles accounted for over 70% of the total degradation, and within the same cycle period, higher overlying stress levels corresponded to greater degradation amplitudes. (3) The increase in overlying stress significantly deteriorated the mesoscopic structure of mudstone, promoting fracture expansion, increasing the contact area of water-rock interaction, and accelerating processes such as the dissolution of calcareous cement and the expansion and contraction of illite and montmorillonite, leading to increased porosity and loose structure of mudstone. The research outcomes offer valuable insights for assessing the stability of clastic rock bank slopes in the Three Gorges Reservoir area.

Biopolymers exhibit extensive application potential in slope ecological protection. In this study, a series of laboratory experiments were conducted to examine the critical properties of xanthan gum (XG) improved sandy soil and its relevance to slope ecological protection. The protective efficacy was confirmed through an XG-plant scouring test. Additionally, microscopic experiments were employed to elucidate the underlying mechanism by which XG augments the ecological protection of slopes. The findings reveal that XG can significantly improve the structural stability of sandy soil, with its effectiveness being closely linked to dosage and curing duration. Under optimal conditions of 1% XG dosage and 28 days of curing, the compressive strength of sandy soil increases from 0 to 1 485.78 kPa, the disintegration rate declines from 100% to 50.99%, the permeability coefficient diminishes by four orders of magnitude, the erosion rate reduces to 1.06 g/min, and the surface hardness reaches 755.09 kPa. XG exerts no detrimental effects on plant growth and, to a certain extent, fosters it. The synergistic interplay between XG and plants enhances the erosion resistance of sandy soil. XG improves the structure of sandy soil via filling and bonding, film coating, and wrapping, forming a dense biological cementation layer on the slope surface. This not only ensures favorable macroscopic properties but also mitigates the impact of rainfall and runoff on the internal slope structure, thereby providing a stable soil-water environment conducive to plant growth and effectively achieving ecological slope protection.

Unsaturated soils exhibit significant time-dependent characteristics under long-term loading and environmental changes. Accurate prediction of their rate-dependent behavior and time effects is crucial for deformation control and long-term stability analysis of engineering structures. Based on the isotach approach for unsaturated soils, a coupled relationship among yield stress, matric suction, and viscoplastic strain rate is established for unsaturated time-dependent soils. To address the discontinuity of viscoplastic rate-dependent parameters during the transition between saturated and unsaturated states, an improved parameter evolution law is proposed. Using bounding surface plasticity theory as the framework and extending the non-stationary flow rule to unsaturated conditions, a constitutive model applicable to triaxial stress states is developed. In this model, the evolution of bounding surface size is governed by viscoplastic volumetric strain, matric suction, and viscoplastic volumetric strain rate. This model effectively captures the coupled effects of viscoplastic strain rate and matric suction on the time-dependent behavior of unsaturated soils. The rationality and effectiveness of the model are verified by comparisons with experimental data from isotropic compression tests, triaxial shear tests, and creep tests on various time-dependent soils under different matric suction levels and axial strain rates. Validation results demonstrate that the model accurately predicts the rate-dependent behavior and creep characteristics of unsaturated soils under specified suction levels.

To address the issues of accurate conversion of the T₂ spectra at different temperatures and the definition of water retention states in low-field nuclear magnetic resonance (L-NMR) unfrozen water tests, this study conducted freezing L-NMR tests on saturated and centrifuged samples. The evolution characteristics of unfrozen water under two conditions were studied, achieving an accurate conversion of T₂ spectra during the freezing process and a precise delineation of the water distribution states. Building upon these insights, the migration mechanisms of unfrozen water in both states were subsequently analyzed. The main conclusions are as follows: (1) A temperature correction method for the freezing T₂ spectra was developed. Using this method, the disparities in the soil freezing characteristic curves (SFCCs) between the two states were scrutinized. It was observed that the unfrozen water content in the saturated samples was consistently higher than that in the centrifuged samples. The variance in water occurrence was pinpointed as the primary contributor to this discrepancy, and the T₂ threshold ranges corresponding to different water retention states were established as follows: film water (0.038−0.396 ms), capillary water (0.396−2.319 ms), and free water (≥2.319 ms); (2) Leveraging the evolutionary traits of unfrozen water and the Gibbs-Thomson effect, the surface relaxation rate p₂ = 49.49 nm/ms was ascertained as suitable for this experimental context. This facilitated the transformation from T₂ distribution to pore size distribution, and r = 58.8 nm and r = 344.0 nm were identified as the boundary pore sizes delineating film water, capillary water, and free water, respectively.   (3) The experiments revealed a temperature threshold at which the migration of film water ceases in both saturated and centrifuged samples. Additionally, the temperature threshold for saturated samples was found to be higher than that for centrifuged samples. It was concluded that the migration cutoff temperature for film water is controlled by the pore water saturation in the capillaries, with samples having higher saturation showing a higher migration cutoff temperature for film water. Both saturated and centrifuged samples demonstrated temperature thresholds at which the migration of film water ceased, with the threshold for saturated samples being elevated compared to that of centrifuged samples. The cessation temperature for film water migration is governed by the pore water filling rate within the capillaries, with samples exhibiting higher filling rates displaying elevated cessation temperatures for film water migration.

China’s diverse terrain and frequent extreme weather events have exacerbated rainfall-induced erosion on slopes. This study introduces an innovative approach by integrating vegetation with microbially induced calcium carbonate precipitation (MICP) technology to improve slope erosion resistance. Through pot experiments and large-scale slope model rainfall tests, complemented by scanning electron microscopy (SEM) and low-field nuclear magnetic resonance microscopic analyses, this study systematically examined the effects of MICP on runoff erosion in vegetation-protected slopes and investigated the erosion resistance mechanisms of MICP-vegetation cooperative protection systems. The results indicate that: (1) Compared with the untreated slope, MICP-vegetation synergistic protection slightly increased runoff but significantly reduced soil loss. The optimal erosion resistance was achieved with a cementation solution concentration of 0.15 mol/L, which reduced runoff and soil loss by 12.37% and 90.74%, respectively, and increased vegetation coverage by 2.13% compared with the bare slope. (2) Microscopic analysis revealed that MICP fills soil pores through calcium carbonate precipitation, with crystal density increasing proportionally to cementation solution concentration. This process enhances soil cohesion and shear strength, ultimately improving soil erosion resistance. (3) During the pre-seedling stage, slope protection primarily relies on MICP-induced chemical cementation, which quickly forms a calcium carbonate bonding layer on the soil surface to stabilize the slope. After vegetation matures, the combined protection mechanism of MICP and vegetation ensures slope stability and significantly mitigates soil and water loss. These findings advance the theoretical framework of MICP–vegetation synergistic slope protection technology and offer scientific guidance for soil and water conservation efforts.

Rainfall-induced hydraulic scouring induced by rainfall is a significant factor contributing to slope instability and failure. To elucidate the impact mechanisms of various geosynthetic reinforcement methods on the hydraulic stability of slopes, laboratory slope hydraulic scour model tests were conducted. Comparative studies were performed on four slope configurations: unreinforced (J1), geotextile reinforced (J2), geotextile and geogrid composite reinforced (J3), and geotextile and geocell composite reinforced (J4). The results indicate that reinforcement materials improve slope hydraulic response characteristics, reduce overall moisture content, and enhance slope stability and drainage performance. Geosynthetic reinforcement reduces both the rate of accumulation and the stabilized value of pore water pressure, significantly diminishing slope earth pressure, settlement, and soil loss. Among the variants, J4 demonstrated the most pronounced effect, followed by J3, while J2 showed relatively weaker performance. Composite reinforcement system enhances slope resistance to erosion, with J4 delivering optimal protective effect in hydraulic erosion tests. The findings offer a reference for selecting geosynthetic reinforcement methods and for studying the mechanisms of slope resistance to hydraulic erosion.

 During deep coal mining, interlayer rock strata subjected to high static stress and low-frequency dynamic load are prone to fracture and instability, often leading to dynamic disasters. To investigate the dynamic response of rock fracture, deformation, and mechanical behavior under low-frequency disturbances, uniaxial compression tests were conducted on perforated sandstone specimens at different loading rates. This study explores the crack evolution, fracture ejection patterns, and dynamic strain behavior of sandstone under disturbance. The results reveal the following key findings: (1) The mechanical properties of sandstone are significantly influenced by the loading rate, with peak strength increasing nonlinearly as the loading rate rises. When the loading rate increases fivefold, the average peak strengths of the single-hole, double-hole, and triple-hole specimens increase by 9.67%, 14.64%, and 9.44%, respectively. However, as the number of perforations increases, the overall load-bearing capacity of sandstone decreases, and the average peak strengths are reduced by 12.58%, 12.15%, and 13.23%, respectively. (2) The acoustic emission (AE) characteristics and stress-time evolution curves of sandstone exhibit distinct inflection points. AE activity is relatively weak during the crack initiation stage, but AE events increase sharply before failure, accompanied by an exponential rise in AE energy. This phenomenon can serve as an early warning indicator of dynamic failure in high-stress sandstone under low-frequency disturbances. (3) Based on the failure modes and the extent of surface spalling and block ejection, sandstone failure can be classified into three types. The mean σ_c/σ_z values for type I, II, and III specimens are 0.959, 0.765, and 0.687, respectively, indicating significant differences in mechanical properties among different failure modes. (4) The strain distribution in the rock specimens is closely related to the number of perforations. As the number of perforations increases, pronounced stress shielding zones and horizontal tensile strain zones develop between the holes during loading, providing the main pathways for crack propagation.

Aging deterioration of the soft interlayer of carbonaceous shale in acid-rich environment is a key factor inducing geotechnical engineering instability. To investigate the deterioration of shear behavior of the weak interlayer under acid corrosion and the underlying acid corrosion mechanism, the Permian weak interlayer from the Huangshan limestone mine in Sichuan province was selected as the study object. Direct shear tests on weak interlayer specimens were carried out after soaking in oxalic acid solution, along with pH monitoring, scanning electron microscopy, and wave velocity measurements. The results show that some mineral components in the weak interlayer react more readily with oxalic acid solution. The pH value of the immersion solution increases with time and eventually shows slightly alkaline. The H⁺ generated by oxalic acid dissociation significantly increases microscopic porosity by dissolving cemented minerals, leading to the deterioration of the longitudinal wave velocity of rock acoustic waves. This deterioration is specifically manifested as an increase in longitudinal wave velocity and a gradual decrease in the wave velocity change rate. Microscopic damage further propagates to the macroscale, specifically manifested as a significant evolution of the shear failure morphology with increasing acidity. Moreover, the stress drop phenomenon during shear failure stage of the weak interlayer after acid erosion is significantly weakened, and the plastic characteristics are notably enhanced. As immersion time increases and solution pH decreases, the cohesion and internal friction angle of the weak interlayer decrease, and the shear strength shows a tendency of gradual deterioration. The reduction in strength is concentrated in the early stage of immersion (0−7 d). Finally, a statistical damage model for rock under chemical-loading was established based on statistical damage theory. The model results were compared with indoor direct shear test results to verify the accuracy and validity of the model.

Natural soil layers typically demonstrate nonlinear compression characteristics and often exist in varying consolidation states during their formation, with the consolidation laws of soil differing under these distinct states. This study takes into comprehensive account the variations in void ratio and permeability coefficient during the soil consolidation process, along with the influence of linear loading, to formulate a one-dimensional consolidation equation for overconsolidated cohesive soil that incorporates these variations. To validate the accuracy and applicability of the proposed theory, a series of joint tests of one-dimensional consolidation and infiltration during consolidation were carried out on the silty cohesive loess in Xi’an, Shaanxi Province, using a GDS advanced consolidator. Following this, the finite difference method was applied to derive the finite difference equation corresponding to the one-dimensional consolidation equation for overconsolidated soils. The consolidation equation was solved by using MATLAB programming, yielding finite difference solutions for pore water pressure, settlement, and the degree of consolidation during the one-dimensional consolidation process. A comparative analysis was conducted between the finite difference solutions, the results from the one-dimensional consolidation-permeability coupled tests, and the solutions derived from Terzaghi's consolidation theory. The findings reveal that the consolidation theory, which accounts for variations in void ratio and permeability coefficient during consolidation, yields results that closely align with measured values and are more congruent with practical engineering scenarios. Additionally, under varying preconsolidation stresses, the consolidation rate, when considering the nonlinear characteristics during soil consolidation, is slower compared to that predicted by Terzaghi’s theory; however, the ultimate soil settlement calculated by both approaches remains largely consistent.

Coral gravel soil (CGS) is a biogenic composite material composed of coral gravels (CG) and clay mineral matrix, commonly found in tropical coastal and reef island regions. This type of soil typically exhibits high porosity, irregular particle shapes, and a high breakage potential, making its engineering behavior significantly different from that of terrigenous coarse-grained soils. Traditional soil mechanics theories often fail to accurately describe the deformation and seepage behavior of CGS. To better understand its compression-induced deformation and permeability characteristics, one-dimensional constant rate of strain consolidation tests were conducted on CGS specimens with varying CG content. The compressibility, permeability, and consolidation characteristics were investigated. Parameters such as skeletal void ratio and particle breakage index were introduced to quantify particle breakage during compression and evaluate its effects on deformation and permeability. Microstructural changes before and after compression were observed using scanning electron microscopy, enabling the development of a micro-mechanistic model of CGS compression–permeability behavior. The results indicate that both CG content and effective stress jointly govern the compression–permeability response of CGS. Under high effective stress and high CG content (greater than 30% by volume), significant particle breakage occurs, leading to a notable increase in compressibility and a significant reduction in both permeability and the coefficient of consolidation. The compression behavior of CGS essentially represents a microstructural evolution from a “skeletal framework” to “densely packed” configuration. The skeletal void ratio e₂ effectively captures this transformation, with a critical value of e₂ = 5 proposed as a threshold to distinguish different microstructural characteristics and their impact on compression–permeability behavior. This study provides mechanical parameters and technical insights valuable for engineering applications on coral reef islands.

Under explosion loading, saturated calcareous sand foundations are susceptible to vibrational liquefaction, posing significant catastrophic risks to superstructures. To investigate this, dynamic model tests were conducted on calcareous sand foundations under explosive conditions, comparing the dynamic liquefaction behaviors of both saturated and electrolytically desaturated calcareous sand foundations. The study reveals that for saturated calcareous sand foundations, the blast-induced liquefaction pattern is intricately linked to explosion vibrations, scaled burial depth, and the evolution of pore water pressure within the soil. The dynamic response of the superstructure is pronounced, with acceleration responses peaking at the bottom and diminishing towards the top. The strain in the superstructure columns is greatest at their bases, and the maximum displacement of the superstructure occurs in the y-direction. Following 300 minutes of electrolytic desaturation treatment with a constant current of 1 A, the saturation level of the saturated coral sand foundation decreases from 100% to 89.5%. Under explosion vibrations, the desaturated coral sand foundation exhibits a roughly 10% reduction in maximum excess pore pressure and an approximately 25% decrease in structural displacement, while the acceleration response of the superstructure remains relatively consistent. These findings demonstrate that electrolytic desaturation measures effectively mitigate the vibration liquefaction of saturated calcareous sand, offering crucial insights for ensuring the safety and stability of geotechnical engineering projects on islands and reefs.

Ground collapse poses a significant threat to urban safety, highlighting the need for effective field monitoring and early detection technologies. In this study, a trapdoor test was conducted to simulate ground-collapse formation. Optical frequency domain reflectometry (OFDR) and particle image velocimetry (PIV) were employed to analyze the strain responses of sensing optical fiber cables at different embedment depths and to investigate factors governing deformation coupling at the cable-soil interface. The results indicate that as the trapdoor descends, the cable strain curves exhibit a bimodal pattern, and the peak locations closely correspond to the shear-band propagation boundaries identified by PIV. The formation of stable soil arches can effectively suppress the propagation of failure surfaces and reduce the peak tensile strains measured by the cables. Increasing confining pressure and installing anchor plates can significantly enhance deformation compatibility at the cable-soil interface. However, if the anchor plate spacing is too small, overlapping soil shear zones may weaken the reinforcing effect of the anchor plates on cable-soil coupling. During collapse process, the anchor plates are significantly influenced by soil shear bands. Once the sensing cable enters an inclined tension state, the torque effect of the anchor plates increases significantly, causing them to rotate under lateral soil compression. The rotation center then gradually shifts toward the geometric center of the plates. This study provides a scientific basis for optimizing ground collapse monitoring schemes and offers references for research on collapse mechanisms and prevention practices.

Large deformation of soft rock tunnels is an engineering and technical challenge that must be addressed to realize the ambition of becoming a leading nation in tunnel construction. However, the intricate relationship between rock deformation constraint/release, rock pressure and lining bearing capacity remains ambiguous, posing theoretical obstacles in selecting appropriate support types and determination of design parameters. To tackle this challenge, this study adopts theoretical analysis method to model and analyze the mechanism of large deformation of soft rock tunnels, attempting to establish a theoretical relationship among these factors. Firstly, theoretical formulations are presented to elucidate the relationship between rock pressure/lining bearing capacity and lining thickness, revealing the theoretical reason why, when the lining thickness is less than a certain critical value, increasing its thickness induces a greater rate of increase in surrounding rock pressure than in the bearing capacity of the lining. Secondly, the generalized Kelvin model is employed to characterize the time-dependent deformation of surrounding rock, and the deformation process of yielding lining is simplified into the deformation release stage and deformation control stage. A tunnel mechanical model describing the interaction between surrounding rock and yielding lining is established, and analytical solutions for tunnel/lining displacement and lining pressure at different deformation stages are provided. The above analytical solutions for yielding lining supported tunnels can further be degenerated to those under the strong support action. Moreover, the reliability and feasibility of the theoretical model established in this study are well verified by comparing with results in previous reference and by applying it in a practical project. Finally, based on the proposed analytical solutions, a comprehensive parametric investigation is conducted, including the deformation capacity of surrounding rock, thickness of strong support, tunnel yielding displacement, and yielding resistance. The results indicate that under some large deformation conditions, if strong support is used, the required lining thickness is excessively large, necessitating the adoption of yielding lining. There exist reasonable ranges for both the yielding displacement and yielding resistance of yielding lining, which should be determined considering the mechanical properties of surrounding rock and lining. The concise tunnel theoretical model provided in this study can play an important theoretical support for the rapid design in the preliminary stage of related projects.

On March 28th, 2025, a catastrophic earthquake measuring Ms 7.9 struck central Myanmar, resulting in extensive damage to buildings, significant casualties and tremendous economic loss. During a two-week on-site investigation, widespread liquefaction phenomena and the consequent damage to structures and infrastructures were investigated across 16 villages (or districts) within the earthquake affected regions. This examination encompassed hundreds of residential houses, two major bridges, several roads, and underground storage tanks, among others. Reports also detailed the consequences of liquefaction-induced lateral spreading, which led to the demolition of houses and casualties. The field survey of liquefaction revealed that the liquefaction phenomena and the associated damage were extensively distributed along the surface rupture, accompanied by substantial sand ejection and severe impacts on structures. Ground fissures resulting from liquefaction constituted a major cause of structural destruction in buildings. The loss of ground bearing capacity remained another impact of liquefaction on structural damage, resulting in subsidence and tilting of buildings. The cases of liquefaction in the Myanmar earthquake reported herein provided experience and lessons for anti-seismic design aimed at mitigating soil liquefaction risks in the Southeast Asia. Through the analysis of the phenomenon and characteristics of soil liquefaction, the methods and techniques for liquefaction hazard mitigation in China can be further refined and improved.

Continuous degradation of the shear properties of joint rock masses caused by aqueous solution erosion is a critical factor affecting slope stability. Therefore, we proposed a dynamic dissolution testing method based on gas-liquid circulation under gas-liquid-solid three-phase coupling conditions. Dynamic dissolution tests and direct shear tests were conducted on joint samples in CO₂ solution environment. The deterioration law of the shear mechanical parameters of the joint samples was characterized. Meanwhile, by combining three-dimensional morphology and microstructure scanning technology, the deterioration mechanism of the joint samples under the dynamic dissolution effect of CO₂ solution was revealed. Results show that the shear-displacement curves of the joint samples can be divided into three stages: initial locking, intermediate failure, and late-stage shear-friction-resistance sliding. As the number of dissolution cycles increased, the shear hardening characteristics and stress levels of the samples decreased. After 30 dynamic dissolution cycles, the internal friction angle and cohesion decreased by 37.78% and 29.73%, respectively. Concurrently, progressive microstructural damage and pore development reduced the joint surface roughness and the compressive strength of joint rock masses, weakened frictional interlocking between joint surfaces, and thereby degraded shear mechanical performance. Finally, a numerical stability model incorporating dissolution-induced degradation of shear parameters was established. Analyses indicate that the decline in the safety factor of jointed slopes is primarily governed by the deterioration of joint shear parameters. Owing to spatial variations in stress states, the potential slip path dynamically migrates from shallow to deeper joints. The methods and findings provide a theoretical basis for long-term stability assessment of joint slopes.

The spatial variability of gravelly soil landslides arises from the combination of units with varying grain size compositions, degrees of difference, unit sizes, and arrangements. These combinations form fundamental structures, referred to as the basic structures of spatial variability, characterized by distinct strength levels, differences, unit sizes, and arrangements. Understanding the mechanical behavior of these basic structures is essential for assessing landslide stability through displacement characteristics. To address this, the study utilizes field investigations and empirical insights, combined with the discrete element simulation software PFC, to develop numerical models of strip blocks with varying basic structures of spatial variability. The mechanical behavior of these structures is analyzed under the application of a thrust force. The results indicate that the characteristics of the basic structures of spatial variability significantly affect the mechanical behavior of gravelly soil landslides. Interactions among units within these structures result in changes to stress distribution, deformation behavior, and stress-strain relationships, highlighting structural effects such as force transmission and anti-sliding resistance. As a result, displacement characteristics differ across various positions of the landslide. Local yielding and cracking develop from weak units to strong units within the structure, progressing from localized to overall failure. During small deformations, strong units primarily bear the load. In contrast, during large deformations, the load redistributes and concentrates on weak units. The deformation direction of the structure is oriented toward its weak units, which determines the magnitude and direction of the force distributed to the sliding zone. The displacement curve clusters on the landslide surface are shaped by the combined effects of the landslide structure, its mechanical behavior, and external forces. Accordingly, this study proposes a method for identifying landslide structural features based on displacement curve clusters, enabling the assessment of structural characteristics—or even specific structures—using these curves. This approach optimizes the layout of monitoring points, thereby improving the accuracy and reliability of landslide monitoring.

During the construction of long-distance large-section water conveyance tunnels across watersheds, small-diameter drilling and blasting pilot tunnels or tunnel boring machine (TBM) pilot tunnels are often used for pilot excavation to explore unknown geological conditions and manage risks associated with the surrounding rock. However, due to the constraints of the construction period and conditions, these pilot tunnels will exist for a relatively long period of time. Therefore, it is necessary to clarify the adjustment and failure laws of strain energy in the surrounding rock of the tunnel under the conditions of pilot tunnels, providing technical support for the excavation of pilot tunnels and subsequent secondary expansion excavation. Initially, this study utilizes numerical simulation to elucidate the adjustment mechanisms of strain energy triggered by pilot tunnel excavation, subsequently corroborating these findings through laboratory and field experiments. The results indicate that during the excavation of the pilot tunnel, the strain energy near the secondary expansion excavation face is initially released, then re-accumulated deep within surrounding rock. The peak value of the re-accumulated strain energy significantly decreases, and the distance between the peak value of the strain energy and the tunnel surface gradually increases and remain stable. Therefore, when the pilot tunnel exists, the degree of rock failure and the amplitude of acoustic emission decrease during the continuous loading experiments of the surrounding rock, and the location of rock failure is far away from the expansion excavation face. Based on the field acoustic monitoring test results, it can be concluded that the stress release depth of the stable section of the pilot tunnel excavation is relatively shallow. As the distance to the tunnel face decreases, the stress-release depth of the surrounding rock increases and may extend beyond the contour line of the secondary enlargement excavation, thereby reducing the disturbance caused by blasting and TBM excavation.

In the southeastern coastal regions of China, granite residual soil (GRS) is widely used as subgrade fill, and its dynamic characteristics merit thorough investigation. Vehicle loads and seismic actions are inherently multidirectional, and the dynamic behavior of soils under such multidirectional cyclic loading differs significantly from that under unidirectional cyclic loading. To explore these effects, a series of horizontal cyclic direct shear tests under normal cyclic loading was conducted on GRS using a large-scale bidirectional cyclic direct shear apparatus. The tests were performed under different normal stress frequencies (0.02, 0.05, 0.1, 0.15, 0.2 Hz), and discrete element method (DEM) simulations were carried out to reproduce and further interpret the bidirectional cyclic behavior of GRS. The results indicate that as the frequency of cyclic normal stress increases from 0.02 Hz to 0.2 Hz, the dynamic shear strength of GRS decreases by 15.29%, the vertical displacement increases by 21.00%, and the energy dissipation capacity improves by 25.71%. An increase in normal stress frequency results in a 6.14% reduction in the maximum number of strong force chains within the particle assembly. Meanwhile, the total and fine contact mechanical coordination numbers increase by 0.64% and 0.81%, respectively. The normal stress frequency primarily influences the contact behavior of fine particles, thereby altering the overall contact characteristics of the soil. Additionally, sliding dissipation, rolling-sliding dissipation, and dashpot dissipation increase by 69.35%, 50.52%, and 92.79%, respectively, with increasing normal stress frequency.

This study focuses on permafrost degradation on the Qinghai-Xizang Plateau under warming and humidification. Using numerical simulations combined with geological surveys and environmental monitoring data from the G0615 Dema Expressway (Xiangride to Huashixia section), the research analyzes how water infiltration accelerates ground ice melting in silty clay layers and the evolution of hydrothermal states. The results indicate that underground ice melting occurs in four distinct stages: rapid temperature rise due to heat absorption by ice, stable temperature rise during the ice-water transition, rapid temperature rise of ice meltwater, and stable temperature rise of ice meltwater. Water infiltration significantly improves heat transfer efficiency at the ice-soil interface, leading to an initial increase followed by a decrease in the cooling range of surrounding soil. Additionally, higher infiltration rates cause the cooling range peak to occur earlier. Underground ice redirects water infiltration, but its melting gradually reduces the obstruction to seepage. For a constant cross-sectional area of ground ice, the time for complete melting decreases as it transitions from a vertical to a horizontal state. Horizontal ground ice melting exerts a greater influence on the temperature and seepage fields of surrounding soil, driven by factors such as hydration heat, ice-water transition, and dynamic infiltration path adjustments. This research offers a theoretical foundation for understanding the catastrophic melting of permafrost on the plateau under warming and humidification, supporting the development of more precise underground ice melting prediction models.