3D printing has emerged as a valuable tool for studying the mechanical behavior of rock replicas under various stress−strain states. This technique enables the creation of an unlimited number of replicas with predetermined properties and a homogeneous structure. Among various 3D printing methods, liquid crystal display (LCD)-based printing offers a cost-effective and high-quality approach for rapid prototyping of rock samples. This study investigates the feasibility of using 3D LCD printing to create rock analogs for geomechanical investigations. We evaluate the microstructure of LCD-printed samples and its influence on their elastic and mechanical properties. To assess these properties, we subjected cylindrical samples to elastic wave propagation and uniaxial compression tests. Our results demonstrate that LCD-printed samples exhibit high homogeneity of elastic properties. The velocities of elastic wave propagation across and along the layers are essentially identical, differing only by the error value. Moreover, Young’s moduli obtained under uniaxial loading are in good agreement with non-destructive test results, indicating a high degree of homogeneity in elastic properties up to 20 MPa. These findings suggest that 3D LCD-printed rock analogs are well-suited for investigating processes in rocks under purely elastic loading. Additionally, the technology’s versatility allows for the creation of rock replicas with various features, providing researchers with the ability to study the mechanical behavior of rocks with specific characteristics. We demonstrate the potential of 3D LCD-printed rock analogs through a case study investigating the impact of cyclic deformations on the conductivity of thin capillaries in a porous medium. Our results provide a strong foundation for utilizing 3D LCD printing to advance our understanding of geomechanical processes in rocks.

Using a self-developed cyclic loading system, the model tests were conducted to investigate the bearing performance of helical anchor piles under horizontal cyclic loading and the influencing factors of soil deformation. Combined with the particle image velocimetry (PIV) technology, the deformation field of the soil around the pile was analyzed, revealing the deformation mechanisms of the surrounding soil under different influencing factors. The results show that: (1) The amplitude and frequency of cyclic loading significantly influence the bearing behavior of helical anchor piles under cyclic loading. Compared to the original static loading scenario, the bearing performance of anchor piles in dense sand exhibits a decreasing trend when subjected to static loading after cyclic loading. (2) The hysteresis loop evolves from an open to a progressively closed shape, with a clear positive offset in the overall response. Under the same cyclic period, the hysteresis loop area increases with amplitude and decreases with frequency. (3) A predictive model for horizontal cyclic cumulative displacement of anchor piles was proposed based on the law of horizontal cumulative displacement, demonstrating satisfactory predictive performance. (4) The embedment ratio, relative density, amplitude, frequency and period of cyclic load have important effects on soil deformation around the pile. The passive displacement field in front of the pile is most sensitive to the loading amplitude, while sand displacement behind the pile is more sensitive to relative density. The shear field in sand is usually parallel and symmetrical with the axis of anchor pile, and the shear strength is positively correlated with the amplitude and frequency of cyclic load, and negatively correlated with the frequency of cyclic load.

Based on the slag extruded precast pile technology and active MgO-CO2 carbonation curing method, the feasibility of using MgO instead of cement as curing agent was studied. Effects of the pre-carbonation duration on the particle gradation, mass and moisture content, and the unconfined compressive strength of MgO-cured compacted soil were investigated by combining the X-ray diffraction (XRD), thermo-gravimetric analysis (TGA), mercury intrusion porosimetry (MIP), and scanning electron microscopy (SEM) tests. The products of carbonization process and microstructure evolution characteristics were analyzed, and the mechanism of the influence of pre-carbonation duration on the strength of MgO-cured compacted soil was revealed. In pre-carbonation duration of 1−5 h, the mass of compacted soil increases rapidly and then tends to slow down with the carbonization time, but the water content shows in the opposite trend. The coefficient of uniformity Cu and the compactability increase with the rising number of particles in size of 1−10 m. The unconfined compressive strength increases rapidly then slows down to be stabilized. During the carbonization process, the carbonization products generated by the carbonation process are wrapped around the soil particle surface to improve the hardness. Morever, the carbonization products fill the large to super larger pores (4−40 m) in soil during the compaction, and MgO continues to hydrate and carbonize during the maintenance stage to further fill soil pores, leading to improve the degree of densification. The three mechanisms described above act synergistically to enhance the macroscopic strength of the cured compacted soil. However, with longer pre-carbonation durations, the formation of a passivating layer inhibits further carbonation. In addition, the initial low water content limits MgO hydration, reducing carbonation during the carbonation stage. These factors lead to a transition from rapid to slower strength development in the cured compacted soil.

Leakage from underground structures within water-rich sand layers readily triggers sand-water outburst disasters, with their destructive behavior closely linked to pore water pressure. Existing research predominantly focuses on single sand layers, leaving insufficient exploration of the entire outburst process and pore water pressure response patterns in composite sand layers. Drawing upon the context of metro construction accidents, this study designed ten sand-water outburst model tests. Employing a real-time pore water pressure monitoring system, it investigated the initiation, development, and stabilization processes of erosion within a “fine-grained upper layer, coarse-grained lower layer” composite sand formation, with particular emphasis on revealing the pore pressure response characteristics during outburst failure. Results indicate that following outburst initiation in composite sand formations, pore water pressure undergoes three distinct phases: a sudden drop, sustained low pressure, and subsequent recovery. The rate and magnitude of pore pressure decline correlate positively with the severity of failure. During cavity expansion, the rate of sand-water loss exceeds upstream water replenishment, inducing negative pressure within the cavity where local head differences exceed overall head differences. Significant permeating forces develop perpendicular to the cavity surface, triggering sand boiling phenomena that exacerbate permeation failure. Experiments reveal that within composite sand layers, the lower coarse sand and upper fine sand form a series structure. The coarse sand layer acts as a strong water supply conduit, concentrating permeation forces primarily on the upper fine sand. This results in longer duration, more severe extent, and broader scope of sand and water loss within composite layers compared to single-layer formations, presenting significantly higher failure risks. Enhanced identification and monitoring are recommended for engineering applications.

Acid fracturing technology is an important method for stimulating carbonate reservoirs and increasing production. Acid etching of fractures significantly enhances fracture conductivity between the wellbore and the reservoir. However, rough-walled fractures in carbonate reservoirs feature extremely complex geometries, resulting in the difficulty to accurately evaluate the dissolution pattern and the fracture conductivity in the process of acid stimulation. Existing studies have not fully considered the effect of fracture roughness on the evolution of dissolution morphology, as well as the effect of nonlinear flow behavior in acidized fractures on the fracture conductivity. Therefore, the effects of fracture roughness, acid injection rate, and acid concentration on the dissolution and conductivity properties of rough fractures are investigated. A dissolution transition model to quantify different dissolution patterns along a rough-walled fracture is established, the effect of dissolution patterns on the nonlinear flow coefficient of fractures was quantified, and a method to interpret the conductivity of the acidized fracture considering non-linear flow effects is further proposed. Three different dissolution patterns are determined by characterizing the acid dissolution morphology along fracture surfaces and the acid breakthrough time, namely, uniform dissolution pattern, channel dissolution pattern and surface dissolution pattern. A channel dissolution coefficient is then defined to capture different types of dissolution patterns. The degree dissolution is deepened as the channel dissolution coefficient increases, and the dissolution patterns change from uniform dissolution pattern to channel dissolution pattern, and then to surface dissolution pattern. When the acid concentration increases, the boundary channel dissolution coefficient that dominates the transformation of dissolution patterns increases accordingly. By comparing the nonlinear flow properties and conductivities of acidized fractures under different dissolution patterns, it is found that the channel dissolution pattern and the surface dissolution pattern feature relatively high conductivity. Considering the influence of factors such as the total acid injection amount and the reservoir stress environment, the channel dissolution pattern is preferred to achieve higher acidizing efficiency.

Grouting is a crucial technique for treating rock fractures in goafs, but it still faces challenges in predicting diffusion patterns and controlling the process; thus, optimization is needed to improve efficiency and effectiveness. As a case study, actual rock fractures in a grouting project for an underlying goaf in Jincheng City, Shanxi Province were used. A fracture model with controllable roughness was constructed, and transparent epoxy resin rough fractures were fabricated by 3D printing. And then, a self-developed visual experimental platform for rough fractures was established to analyze the diffusion characteristics, range, and grouting rate considering different grout concentrations, fracture roughness, grouting pressures and grouting rates, revealing the grouting diffusion mechanism with combination of grout concentration, fracture roughness, and grouting input conditions. And also, the phase interface theory was applied to characterize the diffusion pattern, and the fractal dimension was proposed to describe corresponding diffusion pattern under different conditions. The correlation between actual filling rate and filling capacity was explored, with “actual filling ratio” used as an index for grout filling capacity in rough fractures. These investigations show that grouting diffusion exhibits different patterns depending on grouting pressure, fracture roughness, and grout rheology, with grouting rate and grouting pressure as primary controlling factors and diffusion regulated by rheology and fracture morphology. Furthermore, faster grout diffusion leads to more irregular diffusion contours, which hinders complete filling of complex fracture networks, so the actual filling ratio can explain effective grouting in the fractures considering the combination of high-concentration grout and high grouting pressure. Additionally, a proposed numerical model for rock fracture grouting was established, verifying the reliability of the experimental results. The above achievements provide scientific supports for optimizing grout mixture design, grout hole spacing, and grouting pressure, solving corresponding parameter selection in traditional grouting methods for rock fractures grouting.

Structured clays exhibit engineering properties distinctly different from remoulded soils due to their unique cementation structure and spatial particle arrangement. By analysing the structural evolution characteristics of structured clay during isotropic compression, this study proposes a mathematical model for structural evolution based on yield stress. The model directly utilizes yield stress as a parameter characterizing initial structure, eliminating the need for additional initial structural parameters. Through analysis of compression curves, a relationship between structural evolution and yield stress was established, and a structural evolution mechanism influenced by both plastic volumetric strain and plastic deviatoric strain was introduced. Based on this foundation, the structural evolution model was incorporated into a unified hardening model framework, resulting in an elastoplastic constitutive model that comprehensively considers both initial state and structure. Beyond the parameters of the modified Cam-clay model, this structural model requires only 4 additional parameters, all obtainable through conventional physical and mechanical tests. The predictive capability of the model was verified by simulating compression and shearing processes of a hypothetical soil. Results demonstrate that the model accurately describes mechanical and deformation characteristics of compacted structured clay, including nonlinear volumetric compression, deviatoric stress peaks and strain softening during shearing, and structural evolution with plastic volumetric and deviatoric strains. The applicability and validity of the model were further verified through comparison with experimental data from various structured soils, including Jingyang loess, under different stress paths. The research findings provide a new theoretical perspective for understanding the mechanical behaviour of compacted structured soils, offering practical guidance for engineering applications in regions with structured clay deposits.

Seismic response testing of dry sand sites serves as an effective method for evaluating boundary effects of flexible laminated shear boxes. For this purpose, a centrifuge shaking table model test on a dry sand site was designed and conducted under 50g centrifugal acceleration. Representative near-fault pulse-like and non-pulse ground motions were used as input at the shaking table platform. Acceleration records from sensors installed at various depths within both the central zone and boundary regions of the site were comparatively analyzed to assess the shear box’s boundary effects. The model test results demonstrate that boundary effects diminish with increasing soil burial depth and greater distance from the box walls; furthermore, boundary effects are more pronounced under the pulse-like ground motion. When only ground-motion amplitude is considered, the free-field zone lies at least 3/20 L from the short-side wall and at least 1/5 W from the long-side wall (L = box length, W = box width). When ground-motion spectral characteristics and phase lag are also considered, the extent of the free-field zone requires further determination through experiments. The derived conclusions can provide critical reference for enhancing the accuracy of centrifuge shaking table model tests.

Triaxial impact compression tests of coal specimens were carried out by using the split Hopkinson pressure bar (SHPB) test system. Based on the mechanical test results, the dynamic constitutive relationship of coal specimens was studied. The results show that: (1) The dynamic compressive strength and dissipated energy of coal specimens are positively correlated with the change of confining pressure and impact velocity (strain rate), and negatively correlated with the change of axial pressure. The failure mode of coal specimens under three-dimensional load is shear failure, and the fragmentation of coal specimens varies with mechanical properties. (2) Based on the statistical damage theory, the damage is described by introducing the dynamic Mohr-Coulomb strength criterion to represent the stress change of the micro-unit inside the coal specimens during the test, and the dynamic damage constitutive relation of the coal specimens is established. A genetic algorithm is used to fit the test curves, yielding a high goodness of fit that reflects elastic, plastic flow, strain softening, strain rebound, and other mechanical properties of the coal specimens. The constitutive relation is suitable to describe the dynamic stress-strain relationship of coal specimens under three-dimensional load. (3) Under dynamic loading conditions, the average cohesion and internal friction angle of coal specimens increase by 140.2% and 28.0% respectively compared with those under static loading conditions. Weibull distribution parameters m and F0 strongly positively correlate with dynamic cohesion and dynamic internal friction angle, respectively. It shows that the brittle and hard rock mass has a high dynamic elastic modulus, and the higher the strength of the coal specimen, the greater the dynamic cohesion. (4) The applicability of statistical damage constitutive model and combined component constitutive model is compared and analyzed. In principle, although the constitutive model of combined component can also accurately reflect various mechanical properties of coal specimens during the loading process, the fitting parameters are too many and the model is quite complex. The statistical damage constitutive model has few fitting parameters and can reflect the complex dynamic mechanical properties of coal specimens under confining pressure.

Laboratory self-weight sedimentation tests were conducted on two types of dredged slurry with varying initial water contents and initial sand contents, using different-sized apparatuses to investigate particle sorting characteristics in dredged slurry containing coarse particles during self-weight sedimentation. The study examined the effects of initial particle distribution, initial sand content, and initial water content on the particle sorting threshold of dredged slurry during sedimentation, and identified the key controlling parameters for the particle sorting threshold. The distribution of coarse particles along the specimen height after the completion of self-weight sedimentation was analyzed, and a method for determining the coarse particle sorting interface height was proposed. By normalizing the coarse particle sorting interface height with the stabilized mud-water interface height, a unique linear relationship was established between the normalized coarse particle sorting interface height and the initial sand content, regardless of differences in initial particle distribution or water content. Furthermore, the distribution of fine particles in the sediment layer below the sorting interface was examined, and the key relevant influencing factors were discussed. These findings provide a theoretical basis for the design of dredged slurry storage ponds considering the particle sorting effect.

As a new type of cementitious material, polymers have been widely applied in water conservancy and geotechnical engineering due to its fast cementation speed, high strength, light weight and high flexibility. As a polymer-containing composite, the constitutive model for polymerized rockfill materials remains inadequately studied. To characterize the mechanical behavior of polymerized rockfill materials more comprehensively, we develop a plasticity constitutive model that accommodates non-associated plastic flow, based on fractional-order calculus. The model introduces a modified mean stress that accounts for the polymer gelation effect and unifies the critical-state parameters across different polymer contents. It adopts a two-parameter yield surface and embeds the state parameters, defined by the modified mean stress, into the stress-dilatancy relation and the plastic modulus. Consequently, a stress fractional order plasticity constitutive model for polymerized rockfill materials with state dependence is established. Comparison of model predictions with experimental results shows that the proposed stress-fractional-order plasticity constitutive model effectively captures the strain-hardening and shear-shrinkage behavior of polymerized rockfill materials under drained shear conditions.

The application of underwater vacuum preloading technology has long been limited by difficulties in stabilizing vacuum pressure in marine environments, which restricts its effectiveness in deep-water conditions. To address this bottleneck, this paper proposes a novel underwater vacuum preloading method, which utilizes a large-diameter sleeve anchored in marine clay as the waterless operation system of the vacuum pump, thereby overcoming vacuum-pump pressure loss in the marine environment. Four model experiments compare the consolidation performance of the new underwater vacuum preloading method at different overlying-water depths with a traditional vacuum preloading method that has no overlying water, using underwater soft clay as the test material. Results show that the new method achieves significant consolidation, and the reinforcement effect increases with greater overlying water depth. Compared to the control test T4 with an overlying water depth of 0 m, the reductions in average water content for tests T1, T2, and T3 with overlying water depths of 7.2 m, 4.6 m, and 1.4 m were 43.8%, 31.3%, and 12.5% greater, respectively. The average undrained shear strength of the soil of tests T1, T2, and T3 increased by 39.5%, 25.7%, and 8.7%, respectively, compared to test T4. According to the improved Asaoka’s method, the consolidation degrees of tests T1, T2, T3, and T4 after 40 days were 90.2%, 90.2%, 92.7%, and 95.3%, respectively. This study provides an effective approach for applying underwater vacuum preloading technology in deep-water regions, presenting significant prospects for engineering applications.

A repeated fracture grouting method is proposed to address the limited number and reinforcing effect of main fracture grouted veins in dense and weak strata. This approach enhances the effectiveness of fracture grouting technology by improving the distribution and reinforcement of grouted veins. The method enhances the reinforcement effect in dense weak strata by controlling the timing of multi-stage fracture grouting, increasing the number of main grouted veins within the reinforcement target area, and establishing a network of fracture grout veins. To investigate the impact of repeated fracturing grouting interval time on the diffusion characteristics of different fracturing sequences, physical experiments were conducted on repeated fracturing grouting in typical dense weak media, based on the Xianglushan Tunnel of the Central Yunnan Water Diversion Project. A diffusion mechanical model for the repeated fracturing slurry was established. This paper summarizes the diffusion patterns and morphological characteristics of fracturing slurry under varying fracturing sequences and interval times. Based on the theory of circular hole expansion, a diffusion mechanical model for repeated fracturing grouting is developed, accounting for the influence of intermediate principal stress, along with a corresponding formula for fracturing pressure. The mechanism underlying the directional changes in multi-stage fracture diffusion is clarified. The research reveals that in dense weak strata, an extrusion-diffusion “O-type” vein package initially forms. As the internal pressure of the slurry increases, an “I-type” fractured vein develops along the dominant rupture plane, oriented in the direction of the vertical minor principal stress. As the preceding slurry approaches initial setting, the solidified grouted veins at the fracture tip alter the local stress state, causing the subsequent fracturing channel to change direction non-homogeneously and form a “Y-type” fractured veins by exploiting a new weak plane. A dimensionless parameter, the “volume-pressure ratio”, is introduced based on the analysis of the ratio between grouted volume and fracturing pressure increase. The findings indicate that performing 2−3 repeated fracturing grouting with intervals of 50%−75% of the slurry’s initial setting time facilitates the formation of extensive branching grouted veins, significantly enhancing the grouting effect in dense weak strata.

In response to the limitations of the existing a unified state parameter model for clay and sand (CASM) in simulating the mechanical properties of overconsolidated soil, this paper introduces the theoretical framework of the subloading surface Cambridge (SSC) model and constructs an overconsolidated soil model (CASM-o) based on the SSC and CASM. This model not only retains the advantages of CASM in yield surface and plastic potential surface, but also combines the hardening rule of the SSC model for overconsolidated soil, which can better describe the mechanical behavior of overconsolidated soil. Based on the CASM-o, this paper systematically analyzes the overconsolidation characteristics of four typical clays under three stress paths: conventional triaxial drained, undrained, and constant average principal stress. The results indicate that the CASM-o can effectively capture the strain softening and volume expansion phenomena exhibited by overconsolidated soil in triaxial drainage tests, as well as the strain hardening and negative excess pore water pressure characteristics exhibited in undrained tests. This validates the effectiveness and reliability of the CASM-o in simulating the mechanical response of overconsolidated soil under different stress paths.

Suffusion, a phenomenon involving the migration and loss of movable fine particles through pore channels in internally unstable sandy soil, is one of the primary triggers of seepage failure in poorly-graded geological bodies or geotechnical structures such as dams. However, existing models of suffusion rate often suffer from limitations such as strong empirical dependence, poor parameter measurability, and unclear physical significance. To address these issues, this study explains why the total amount of erodible fine particles in sandy soil remains finite, from the perspectives of suffusion meso-mechanisms and energy dissipation. Suffusion is defined as an energy dissipation process induced by the mechanical work performed by fine particles within the soil matrix. Subsequently, through analysis of the intrinsic mechanisms and energy conversion during suffusion, a suffusion rate model for sandy soil under constant hydraulic gradient is proposed. The model introduces the maximum cumulative loss ratio and the erosion coefficient as key parameters. These parameters are expressed as functions of critical factors such as experimental conditions and soil characteristics, which are determined and calibrated based on the energy dissipation principle and dimensional analysis, respectively. Finally, the model’s validity is verified using experimental datasets from published literature. The results demonstrate that the proposed suffusion rate model for sandy soil effectively captures both the finite total loss of fine particles and the decay characteristics of the suffusion rate. Utilizing a single set of parameters, the model successfully describes the fine particle loss process for the same soil type under different constant hydraulic gradients. The development of this model enhances the understanding of the intrinsic mechanisms governing suffusion in sandy soil and establishes a theoretical basis for the quantitative analysis of suffusion processes.

Loose deposits are extensively distributed in natural environments and are frequently destabilized by external disturbances such as rainfall, which can trigger debris flow disasters. During rainfall, fine particles in the loose deposits combines with rainwater, forming a mud that induces instability. In order to investigation the change of shear strength, large-scale shear tests of loose deposits saturated with different water contents of mud are conducted for the first time by a self-developed large-scale shear testing apparatus capable of conducting shear tests under saturated conditions. There are some findings. (1) Relative density range of loose deposits is 0.35–0.45. Below a relative density of 0.35, loose deposits tend to settle under gravity, leading to an increase in relative density. Conversely, above 0.45, the deposits no longer exhibit loose characteristics. (2) Mud properties correlate with water content. As mud water content increases, cementation weakens and lubrication strengthens. The minimum water content required to form mobile mud is 66.6%. Below this threshold, the mud loses its fluidity. At 90.9% water content, the mud’s fluidity approaches that of water. (3) Mud weakens the shear strength of loose deposits. As mud water content increases, the internal friction angle (φ) and cohesion (c) of loose deposits decrease. The looser the deposits, the greater the weakening effect of the mud, and the more prone they are to instability. The variation in shear strength of loose deposits saturated with different water contents of mud explains the mechanism of debris flow after short-term heavy rainfall.

The aging of EPDM sealing gasket for shield tunnel segment joints during operation will lead to stress relaxation and attenuation of waterproof performance. The current rubber aging model cannot evaluate the long-term stress relaxation of waterproof gasket under non-uniform compression. In this paper, a hyper-viscoelastic aging model of long-term stress relaxation of rubber at different temperatures and strain levels is established by theoretical method, and numerical implementation is carried out in the ABAQUS. The aging test and waterproof test of sealing gasket are further carried out, showing that the waterproof performance of the waterproof gasket aging for 3 days under the condition that joint opening 6 mm, no dislocation and 70 °C is about 27% of the unaged gasket.The results obtained from numerical simulations based on the aging model align well with the stress relaxation test results of sealing gaskets and the waterproof performance test results of aged sealing gaskets, verifying the applicability of the super-viscoelastic aging model in evaluating the long-term mechanical and waterproof performance of sealing gasket components in shield tunnel segment joints. The evaluation results of the aging model after numerical implementation indicate that the sealing gasket, after being aged for 3 days under the condition of 70℃ and a joint opening of 5 mm, corresponds to a service life of 91 years under the condition of 25℃ and a joint opening of 5 mm. Finally, the long-term waterproof performance of gasket in Nanhu Tunnel is analyzed, showing that the waterproof performance can reach 0.8 MPa after 100 years of service in 25 ℃ when joint opening is smaller than 7 mm, which meets design requirement.

For ultra-soft soils such as sludge, traditional single-method reinforcement often fails to achieve satisfactory stabilization. Assuming free strain and accounting for the smear effect, multi-stage loading, and time-dependent vacuum pressure, we derive an analytical solution for radial consolidation of soil under the combined effects of electro-osmosis, vacuum, and staged loading, using Bessel functions and the method of characteristic functions. The solution was verified by comparing the model degradation with existing solutions and laboratory test data. Subsequently, we examined the effects of multi-stage loading, the permeability coefficient, and vacuum pressure on soil consolidation. Results indicate that, compared with single-stage loading, multi-stage loading more effectively reduces excess pore water pressure during loading and prevents sharp increases in pore water pressure. Reductions in the electro-osmotic coefficient within the smear zone significantly delay pore pressure dissipation and slow soil consolidation. The hydraulic conductivity has little effect on pore pressure in the early consolidation stage but markedly affects the later stage; thus the smear effect under combined preloading cannot be ignored. The consolidation in undisturbed soil zones is more significantly influenced by electroosmosis, while consolidation in smear zones is more affected by vacuum pressure.

Studying the uplift failure of overlying strata in lined hard-rock underground chambers in metal mines for compressed air energy storage (CAES) holds important theoretical and practical significance for promoting the large-scale and commercial application of CAES technology. The non-linear Hoek-Brown failure criterion was used to investigate the uplift failure mechanism of the strata overlying underground chambers in metal mines under the high internal pressure of CAES based on expressions of the established geological strength index (GSI) and disturbed factor D for characterizing the velocities of sound waves and seismic waves. Additionally, the influence patterns of relevant factors on the uplift failure and ultimate internal pressure of the chambers were explored. The results show that the proposed analysis method for uplift failure of CAES chambers based on the Hoek-Brown criterion of wave velocities in rocks considers key factors and therefore is more comprehensive and reasonable than conventional methods. These factors include the overburden strength, rock mass structure, excavation and blasting-induced disturbance, and lateral pressure coefficient. As the uniaxial compressive strength of rocks, the wave velocity in the undisturbed rock mass, and wave velocity in the disturbed rock mass increase, the uplift failure range of those strata overlying the chambers gradually increase and the required ultimate internal pressure increases accordingly. Meanwhile, the stability of CAES chambers is also enhanced. Due to excavation-induced unloading of ore bodies, the lateral pressure coefficient k of the surrounding rock changes, significantly affecting the uplift failure of those strata overlying the CAES chambers. As the lateral pressure coefficient k increases, the angle a  of fracture surfaces in overlying strata gradually decreases, and the rate of this decrease also exhibits a declining trend. The research provides a basis for the stability evaluation of rocks surrounding underground chambers in mines used for CAES and a design criterion to prevent uplift failure.

The geotechnical issues arising from the large-scale development of underground spaces, primarily driven by urban rail transit, are becoming increasingly prominent. One of the key issues is the anti-floating performance of subway station structures. Based on the subway station project, a monitoring plan has been developed. Water-level and meteorological monitoring points were established around the site. Pore-pressure sensors were installed at the base of the station to enable real-time monitoring for two years. Pore-pressure, on-site water level, and rainfall data have been collected for the entire period from construction to operation. Moreover, the variations in pore pressure and their influencing factors were analyzed. The test and analysis results indicate that the pore pressure at each point of the base dynamically changes and responds promptly to dewatering and rainfall. Dewatering can effectively reduce the pore pressure of the foundation. The pore pressure will increase after stopping dewatering in local area, with a maximum growth value of 76.8 kPa and a maximum growth rate of 213%. The growth value and growth rate of pore pressure are closely related to the depth, distance to the monitoring area, and amount of water in the area where dewatering is stopped, and the distance has the greatest impact, followed by the amount of water to be stopped. Rainfall will increase the pore pressure, and the increase in pore pressure caused by moderate to heavy rainfall is greater than 0.04 kPa/mm. Moreover, the increase in water level and pore pressure after rainfall will lag behind by 4 to 5 hours. The average pore pressure ratio during subway operation varies between 0.84 and 0.96, with higher values during the wet season. The pore pressure test values are basically equal to the static water pressure values. It is necessary to set a safety factor of 1.05 in anti-floating design. The research results can provide reference for subway station construction and anti-floating design.

To investigate the impact of distributed post-grouting technology on pile foundation-bearing capacity, the grout diffusion mechanism and soil reinforcement effects of this technology were intuitively analyzed through model pile excavation tests. Furthermore, based on the self-balancing load test results of three large-diameter bored piles from the Yuanyang to Zhengzhou section of the Anyang to Luoshan Expressway project, the differences in bearing behavior of large-diameter post-grouted piles before and after distributed grouting were analyzed. The influences of the length-to-diameter ratio and the holding layer on pile foundation bearing capacity and grouting effectiveness were thoroughly explored. The results of the study show that: The distributed post-grouting process can realize small spacing, high density and multi-section grouting, which is more capable of improving the pile-side mud skin and soil disturbance problems of the bored pile construction compared with the combined post-grouting, and there is a significant difference in the mechanism of grout diffusion and reinforcement effect in different soil layers. Both distributed post-grouting and combined post-grouting can significantly improve the bearing performance of pile foundation, and the ultimate bearing capacity is increased by 116%−121% and 118%, respectively, while distributed post-grouting shows better improvement in the late loading stage, and at the same time, the length-to-diameter ratio as well as the holding layer both have significant influence on the bearing capacity of the test piles before and after grouting, as well as the effect of grouting. Compared with the combined post-grouted piles, the distributed post-grouted piles are more efficient in grout utilization and their axial force is slightly larger; while in the distributed post-grouted piles, the grouting effect of the test piles in the fine sand holding layer is better than that of the test piles in the pulverized clay holding layer. Distributed and combined post-grouting have significant reinforcement effects on the soil at the pile side, but the small spacing and high density of the distributed post-grouting process results in a more centralized distribution of friction enhancement coefficients at the pile side. The pile tip resistance of test piles with different holding layers is significantly increased after grouting, and the distributed post-grouted piles with fine sand holding layer have greater pile tip resistance enhancement coefficient due to grout infiltration and cementation.

Open-ended precast hybrid reinforced concrete (PRC) piles exhibit distinct vertical bearing behavior compared to closed-ended counterparts, primarily due to soil plug formation during installation. To quantitatively assess this difference, fiber bragg grating sensors were embedded during pile fabrication, and vertical static load tests (SLTs) were conducted on piles P1–P6 with two end configurations and pile lengths. Experimental results for piles P1–P3 were validated through numerical simulations, and length optimization was performed. A parametric study was conducted to evaluate the effects of key geometric parameters on vertical bearing capacity. Results showed that, under identical pile length and stratigraphic conditions, open-ended piles exhibited lower ultimate bearing capacity (UBC), top settlement, and rebound rate than closed-ended piles. However, longer open-ended piles demonstrated significantly greater settlement and rebound than shorter counterparts. Optimization analysis indicated that the closed-ended pile could be reduced from 40 m to 35 m. With constant concrete volume, the D800t130 pile type yielded optimal performance, achieving the highest compressive coefficient (0.42) and material utilization rate (783.1 kN/m³). Both UBC and end resistance ratio increased with pile diameter. For closed-ended piles, diameter significantly influenced axial force distribution and side resistance, while wall thickness had minimal effect on end resistance but reduced side resistance. In contrast, open-ended piles exhibited greater sensitivity to both diameter and wall thickness in terms of axial force and lateral resistance. Inner wall friction was concentrated within twice pile diameters above the soil plug base, although its magnitude remained low. The height-to-diameter ratio (h/D) of the soil plug critically affected vertical bearing behavior. Compared to closed-ended piles, open-ended piles showed reduced lateral friction, with reduction coefficients ranging from 0.78 to 0.92. Notably, when diameter increased from 600 mm to 800 mm, open-ended piles outperformed as closed-ended piles in stiff plastic silty clay.

Ground motions at liquefied sites exhibit distinct characteristics. Clarifying their impact on the damage to superstructures is fundamental for rational seismic fortification in engineering. Using actual seismic-damage data, this study reveals how ground motions at liquefied sites influence structural damage via fragility analysis of typical building types. Against the backdrop of the 2011 M6.3 earthquake in New Zealand, we have compiled actual seismic records from both liquefiable and non-liquefiable sites, and constructed fragility analysis models for two archetypal buildings: a single-story residence and a six-story structure. Using the widely used OpenSees software, we compute the seismic fragility of structures under records from liquefied and non-liquefied sites, respectively. The difference between the results is defined as the fragility increment due to liquefaction and is compared with observed seismic damage. The influence mechanism and degree of seismic ground motion in liquefiable sites on the vibration response of two typical buildings are proposed. The findings enhance the understanding of the influence of liquefied sites on engineering structural damage and can provide guidance for advancing the theoretical development of seismic design for structures on liquefiable sites.

Accurate description of rainfall infiltration is essential for understanding the slope instability mechanism and for preventing and controlling rainfall-induced landslides. Currently, numerical solutions of the Richards equation and the Green-Ampt model are widely used to analyze rainfall infiltration in slopes. Although the Richards equation yields high accuracy, it can suffer from low computational efficiency and convergence issues. Moreover, the classic Green-Ampt model neglects soil stratification and unsaturated-transition layers, and thus cannot accurately represent rainfall infiltration in heterogeneous, multi-layered slopes. To address these limitations, we introduce the concepts of equivalent hydraulic conductivity and elliptical transition layer theory and dynamically simulate rainfall infiltration in heterogeneous, multi-layered slopes. Based on this framework, an improved Green-Ampt model is proposed. The model addresses two key challenges: (1) modifying the calculation formula for the equivalent hydraulic conductivity to describe water migration as the wetting front crosses interfaces between soil layers; (2) deriving a parametric analytical equation for the elliptical transition layer to efficiently compute the spatial distribution of slope volumetric water content for different rainfall durations. Results show that the proposed model yields seepage, stability, and reliability analyses that are highly consistent with Richards equation solutions under both homogeneous and heterogeneous conditions, particularly in the early rainfall stage. Moreover, the model offers high computational efficiency and does not suffer from convergence issues, thereby providing strong theoretical support for reliability analysis of complex slopes and for the prevention and control of rainfall-induced landslides.

Extraction-induced mechanical weakening of methane hydrate-bearing sediments can potentially trigger submarine landslides, but a comprehensive understanding of the underlying progressive failure mechanisms remains lacking. This study used the discrete element method (DEM) to simulate direct shear tests on methane hydrate-bearing sand (MHBS) and systematically investigated how peak strength, structural yield strength, and residual strength varied with vertical stress and saturation. We examined shear-band evolution in MHBS across different hydrate saturations and established links between macro-mechanical responses and microstructure parameters during progressive shear failure. The numerical results revealed that: (1) The numerical simulation results effectively captured the macro-mechanical response characteristics of MHBS. Peak strength, residual strength, and structural yield strengths, all showed consistent positive correlations with hydrate saturation. Additionally, hydrate cementation led to significant nonlinearity in the peak strength envelope of MHBS. (2) The mechanical properties of MHBS intrinsically depended on hydrate cementation. Under a vertical stress ( ) of 1 MPa, the hydrate cementation acted as the primary mechanism resisting external stresses. Upon reaching peak stress, the number of hydrate cementation failures increased sharply, leading to a progressive transition in which interparticle frictional contacts became the dominant stress-resistance mechanism. At = 10 MPa, the load-bearing role shifted predominantly to the sandy soil particles, with a corresponding reduction in the influence of hydrate cementation, consequently leading to enhanced overall compaction. (3) Macro- and microstructural parameters exhibited significant correlation with the initiation and evolution of shear band. Under lower confining pressures, the higher the hydrate saturation, the more concentrated the cementation failure within the shear zone. Additionally, the formation of the shear zone was accompanied by substantial cementation failure. The particle rotation rate and void ratio within the band were significantly higher than those outside, whereas the mechanical coordination number and residual cementation rate were lower. Under high confining pressures, hydrate cementation experienced severe damage, while the specimen exhibited pronounced volume reduction characteristics.

To explore rock strength characteristics and fracture mechanisms under different cooling methods, limestone subjected to high temperature was naturally cooled or water-cooled. Brazilian splitting tests and acoustic emission measurements were performed on the limestone samples after high-temperature treatment, tensile strength under different cooling methods was measured, and the tensile and shear crack evolution during failure was analyzed using a K-Means algorithm. A numerical model of limestone was constructed by using PFC, and the influence of temperature and cooling mode on the tensile strength, crack evolution, displacement field and force chain of limestone was analyzed. The results show that: (1) The tensile strength of limestone decreases with the increase of temperature, and the strength of limestone cooled by water is lower than that under natural cooling conditions. Compared with the limestone without high temperature treatment, the tensile strength of naturally cooled limestone at 200−600°C decreases by 21.8%, 62.8% and 77.3%, and the tensile strength of limestone cooled by water decreases by 54.5%, 65.3% and 79.2%. (2) As temperature increases, pre-peak acoustic emission events increase and internal damage accumulates; tensile cracks are observed throughout loading, while shear cracks occur mainly near the peak and post-peak stages. (3) With increasing temperature, crack complexity increases; under water cooling, the main crack arises from numerous cracks, event magnitudes become more frequent, the displacement field becomes more irregular, and the stability of force-chain networks decreases.

Current numerical simulation studies on water intrusion failure characteristics of mudstone usually update the whole model mesoscale mechanical parameter as the calibration method, which cannot accurately reflect the differences in mechanical responses of specimens under different conditions. To improve accuracy, the simulation method should be updated to reflect the actual failure behavior of mudstone. Relative moisture content (RMC) is introduced to characterize the direct effect of mudstone under different humidification/heating conditions. The general model and the variant stratification (VS) model were constructed, and the mesoscale mechanical parameters were calibrated using the relationship between macroscopic uniaxial compressive strength and surface micromechanical strength to analyze the cementation failure characteristics of each specimen. The results showed that the macroscopic and microscopic strength of the specimens under different humidification/heating conditions varied significantly, and the uniaxial compressive strength weakened with the increase of RMC. The strength of the specimens showed an obvious linear correlation with the thickness of the VS model anisotropy. Compared with the general model, the number and percentage of tension damage cracks and shear damage cracks of the VS model were different, while the damage patterns under different water intrusion conditions were more consistent with the actual test results. Under different conditions, the general model changed significantly for the peak strain energy and cementation energy, while the VS model showed a gentle transition. By analyzing strength variation, damage patterns, and energy release in the simulated specimens, we revealed the mudstone cementation failure characteristics and validated the results for the VS-model specimens.

The micro-electro-mechanical system (MEMS) acceleration sensor has the advantages of small size, light weight, high measurement accuracy, and real-time monitoring, allowing it to achieve accurate angle measurement in centrifuge model tests. This paper introduces a centrifuge angle measurement system based on multi-axis MEMS sensors, including sensor measurement principle, system structure, and sensor characteristics. The typical spectrum of the basket was obtained by centrifuge vibration monitoring, and the feasibility of the system applied to centrifuge angle measurement was verified by a set of centrifuge static angle stability tests and dynamic accuracy tests. The results showed that the measurement error of the sensor was always less than 1% in the static test above 10g, and the measurement error was less than 0.5% when the centrifugal acceleration was stable at 40g; the centrifugal acceleration remained stable at 50g during the dynamic test, the sensor was highly consistent with the on-board angle encoder output, and the average error was 1.13%. The test results demonstrated that the angle-measuring system exhibits good response accuracy and stable performance, providing a novel method for angle monitoring in centrifuge tests. This system has a wide application prospect and significant value.