The Large Deformation Engineering Analysis System (LDEAS) is a specialized finite element software designed for analyzing large deformation mechanics, supporting design, and evaluating stability in deep soft rock engineering. The first version of the software, LDEAS 1.0, was developed in 2007, and its main features include: (1) the capability to perform both polar and additive decomposition analyses for large deformations, as well as the ability to solve three types of nonlinear problems—geometric, physical, and contact nonlinearities; (2) the inclusion of rock mass, joint, and support structure elements, enabling calculations for initial in-situ stresses and dynamic simulations for construction and support; (3) the development of the computation program via the Finite Element Program Generator (FEPG) based on low-code programming technology. To address the limitations of the first version and enhance the software, development of the second version, LDEAS 2.0, commenced in 2020. The main improvements and upgrades encompass three key aspects: (1) the introduction of the NPR bolt/anchor element and an implicit damping iteration algorithm for the renewal of elastoplastic stresses, enriching the variety of support structure elements and improving convergence and iteration speed for elastoplastic calculations; (2) an upgrade of the source code for the finite element computing program from Fortran to C language, enhancing fluency, efficiency, and readability; (3) the development of a new integrated interactive user interface and the inclusion of parallel computing, significantly improving user experience and the efficiency of large-scale computations. Test examples and typical engineering cases have validated the correctness, reliability, and practicality of LDEAS 2.0. The upgrades and development of both versions of LDEAS facilitate comparative studies of two major finite deformation theories and investigations of the rock-bolt coupling effects of NPR bolts/cables, providing reliable software for research on deep rock mechanics issues in China, which holds significant theoretical and engineering application value.

Fluid flow and dissolution in fractured rock widely occur in natural and engineering settings, such as karst development, long-term seepage control of dam foundations, and efficient oil and gas production. As an intrinsic property of fractures, roughness plays a key role in dissolution dynamics, yet its influence mechanism remains insufficiently understood. In this study, a Darcy-scale flow-dissolution numerical model based on the depth-averaging method is developed, and a series of laboratory experiments on flow and dissolution in rough salt-rock fractures are conducted to validate the accuracy and reliability of the simulations. On this basis, the evolution of dissolution patterns, permeability, breakthrough time of dissolution channels, and optimal injection rate is systematically investigated under different fracture roughness and flow rates. The results show that, with increasing flow rate, the dissolution pattern evolves sequentially from compact dissolution to wormhole and then to uniform dissolution, and the corresponding relationships between permeability and fracture aperture exhibit sub-cubic, super-cubic, and cubic trends, respectively. At a given flow rate, increasing fracture roughness enhances local flow heterogeneity, leading to the coexistence of high-velocity channels and low-velocity stagnant zones, which promotes preferential growth of dissolution channels, accelerates wormhole formation and breakthrough, and thus shortens the channel breakthrough time. However, once roughness exceeds a certain threshold, pronounced flow bifurcation and dispersion occur near the wormhole tip, weakening the positive feedback between flow and dissolution and causing the breakthrough time to level off. Further analysis indicates that larger roughness requires higher injection rates to maintain the coupled positive feedback between flow and dissolution and to sustain a typical wormhole, implying that the optimal injection rate increases with roughness. This study elucidates how fracture roughness regulates flow heterogeneity and flow–dissolution feedback to govern channel formation, breakthrough, and optimal injection rate. The findings provide important guidance for predicting early-time leakage in dissolution-driven seepage evolution and for determining optimal injection rates in acidizing stimulation engineering.

To investigate the mechanical behavior and failure characteristics of layered rock masses under complex three-dimensional stress states, true triaxial unloading tests were conducted on layered sandstone using a QKX-YB200 true triaxial testing apparatus, considering varying bedding angles ( ), lateral confinement, and unloading directions (unloading the intermediate principal stress ( ) and the minimum principal stress ( )). The results show that: (1) larger lateral confinement will increase the elastic modulus of layered sandstone under different unloading directions. The peak strength   is minimum at  = 60° and maximum at  = 40 MPa under unloading  .   increases monotonically with the increase of   under unloading  . The spatial relationship between lateral confinement and bedding plane will affect the peak strength of the specimen. In addition, the dependence of   on   decreases with the increase of  . (2) The failure modes of layered sandstone under true triaxial unloading can be divided into dominant failure along layer, dominant failure across layer longitudinally, dominant failure across layer transversely, dominant failure along layer - across layer longitudinally. The higher   is more likely to induce dominant failure along layer-across layer longitudinally under unloading   (except  = 0°). The failure mode is dominant failure across layer transversely under unloading  . (3) The proportion of tensile cracks decreases first and then increases with the increase of   under unloading  . Regardless of the unloading direction, the lateral confinement has an inhibitory effect on the development of shear cracks. The degree of fragmentation of the sample is positively correlated with   and lateral confinement when the lateral confinement surface is perpendicular to the bedding plane, while it is negatively correlated with the lateral confinement when the free surface is perpendicular to the bedding plane. (4) The relationship between the strength parameters of rock mass (cohesion and internal friction angle) and bedding angle   is established. A modified Mogi-Coulomb strength criterion considering   is proposed. It is shown that the criterion has great advantages in predicting the true triaxial unloading strength of layered sandstone by comparing with the experimental results. (5) Combined with the stress state of the bedding plane, the failure mode of the specimen and the fractal characteristics, the influence of the bedding angle, the lateral confinement and the unloading direction on the macroscopic crack propagation degree of the layered sandstone under the true triaxial unloading condition was discussed.

Intelligent blasting is a fundamental aspect of intelligent mine construction, where the compressive strength of the rock mass is a crucial parameter that characterizes the energy characteristics of blasting. To facilitate accurate and rapid predictions of rock mass compressive strength in blasting zones, an electromagnetic-mechanical response model was established, linking radar waves to rock mass compressive strength by integrating Maxwell?s equations with mechanical parameter equations. A novel neural network architecture was specifically designed to train and learn the parameters of this model. Utilizing ground-penetrating radar data and drilling-while-drilling data collected from open-pit mining areas, and incorporating rock mass density as input while constraining the drilling rate, the neural network was employed to predict regional rock mass compressive strength. Experimental results demonstrate a significant electromagnetic-mechanical response relationship between radar waves and rock mass compressive strength. The prediction accuracy of the proposed model exceeds 90%, confirming the feasibility of inverting rock mass compressive strength using radar wave data. In comparison to traditional backpropagation (BP) neural networks, the model developed in this study achieves higher prediction accuracy. Moreover, the three-dimensional compressive strength attribute model derived from the inversion clearly illustrates the spatial distribution patterns and variation trends of rock mass compressive strength. This methodology enables efficient, non-destructive inversion of rock mass compressive strength and offers substantial engineering value for guiding blast hole design, optimizing blasting parameters, and enhancing overall blasting efficiency.

A composite cemented backfill system incorporating magnesia, fly ash, and tailings was developed to address the challenge of low-cost utilization of solid-liquid waste generated from underground Sylvinite mining. An orthogonal experimental design with three factors at three levels was employed, focusing on binder content, the mass ratio of brine to tailings, and fly ash content. A series of tests were conducted on the cemented specimens, including uniaxial compression tests, acoustic emission monitoring (AE), scanning electron microscopy (SEM), and energy dispersive spectroscopy (EDS). The variations in compressive strength and elastic modulus of specimens at different factor levels were investigated. An optimal formulation of the composite cemented material was established. The energy dissipation characteristics during various loading stages were analyzed, and the micromorphology of hydration products within the specimens was examined to elucidate the composite cementation mechanism of the solid-liquid tailings. Additionally, the contribution weights of different factors to the damage variable were quantified, leading to the establishment of a damage constitutive model for the magnesia-fly ash-tailings composite under varying factors and levels. The results demonstrate that the optimal specimen, with a binder content ratio of 1:5, a brine-to-tailings ratio of 1:5, and a fly ash content of 25%, achieves a peak compressive strength of 4.51 MPa. The brine-to-tailings ratio was identified as the primary factor influencing mechanical properties. The failure mode was governed by the fly ash content, transitioning from tensile splitting to shear failure while exhibiting significant plastic residual deformation as the fly ash content increased. The AE activity exhibited three distinct stages: initial quietness, rapid growth, and post-peak quietness. Higher levels of binder and fly ash content, combined with a lower brine-to-tailings ratio, enhanced the energy release per AE event, as well as both the cumulative event count and the total cumulative AE energy. These changes significantly accelerated micro-crack development and improved the connectivity of macroscopic fractures. Based on cumulative AE energy and factor contribution weights, a segmented damage constitutive model for the composite backfill was developed. The theoretical calculations from this model closely matched the experimental data, effectively capturing the stress-strain relationships and damage evolution processes across specimens with different mix proportions. This study provides a foundation for the development of cemented backfill technology utilizing solid-liquid tailings from underground potash mines.

The stress corrosion failure of rock bolts is one of the key factors inducing the instability of coal and rock in coal mine roadways. To reveal its failure mechanism and improve the durability and reliability of rock bolt support, this study combines laboratory experiments, numerical simulations, and field tests to investigate the stress corrosion failure mechanism and control methods for rock bolts. The results show that the fracture cracks of the failed rock bolts underground exhibit a branched pattern, with oxides and Cl elements accumulating in the cracks. Additionally, the bolt body exhibits transgranular fracture characteristics, consistent with the typical stress corrosion failure mode. Laboratory stress corrosion tests further indicate that the stress level is a critical factor promoting the decay of the load-bearing performance of rock bolts in highly corrosive environments. The tests also found that the thread chamfer at the bottom of the bolt is prone to stress concentration due to external loads, with the degree of concentration being influenced by thread parameters. This reveals a fracture failure mechanism caused by the interaction between stress concentration and stress corrosion cracking (SCC) resulting from the bolt shape. Based on this mechanism, a new type of rock bolt was developed to effectively alleviate surface stress concentration. Under compound loading, the plastic zone range of the new bolt was reduced by 23.35%, significantly reducing the risk of stress corrosion failure. Hydrogen content analysis and the examination of typical hydrogen embrittlement features, such as white spots, revealed that the hydrogen content in galvanized rock bolts increased by 304.48% after underground service, indicating that galvanization significantly increases the risk of hydrogen embrittlement failure. To address the limitations of galvanized rock bolts in deep, highly corrosive environments, a surface anti-corrosion and full anchorage protection method was selected, utilizing flexible alloy coatings, single-component cement-based grouts, and thixotropic anchoring agents. A corrosion prevention and grading design method for rock bolts in coal mine roadways was established, and engineering application verification was successfully conducted, achieving safe and efficient control in deep, highly corrosive roadways.

As metallic and non-metallic mines increasingly adopt cemented filling methods, the quality of in-situ cemented backfill becomes crucial for safe mining operations. Based on the layered structural characteristics of in-situ cemented backfill, a quantitative index of continuity (BID) was proposed using the core sample block division standard. In conjunction with the apparent characteristics of the in-situ backfill core samples, a grading system for core integrity was established. The reliability of the structural stability of the in-situ cemented backfill was assessed through a coupling analysis of the exposed characteristics of the backfill and the strength data from core samples. Building upon this foundation, a quality grading standard for in-situ cemented backfill was proposed for the first time, incorporating qualitative classification and quantitative assignment of four indicators: BID, apparent characteristics, structural reliability, and average strength. Additionally, the target strength and adjustment coefficient of the backfill under current quality control measures were determined. This grading standard addresses the existing gap in quality evaluation for in-situ cemented backfill both domestically and internationally, offering evaluation indicators that are straightforward, rapid, and highly applicable in engineering contexts.

Nano-scale coal-rock CT imaging offers the advantages of high resolution and three-dimensional structural reconstruction; however, its acquisition is expensive and its axial resolution is limited, which compromises digital core modeling and seepage simulation. To enhance axial resolution while preserving the true topological structure, this study proposes a generative adversarial network-based super-resolution reconstruction method, termed SRGAN-CT. The proposed method integrates residual blocks and a perceptual loss, and develops a specialized discriminator to strengthen the discrimination of structural details. In addition, a transverse-slice mapping strategy is adopted to construct the training dataset, and orthogonal experiments are conducted to evaluate the robustness and generalization performance of the model. The results show that SRGAN-CT effectively preserves both fine details and topological structures of nano-CT images under multiple upsampling factors and random perturbations, outperforming conventional super-resolution methods in terms of structural-metric deviations and topological errors. Overall, this study verifies the high-fidelity reconstruction capability of SRGAN-CT for 3D topological and geometric information, providing a new technical pathway for efficiently obtaining high-resolution digital cores.

To investigate high-resolution detection methods for meter- to sub-meter-scale hazard sources in underground engineering, this study conducts high-frequency acoustic physical modeling experiments. First, a physical model incorporating multiple types and combinations of karst bodies is constructed based on the typical distribution characteristics of hazard sources. Subsequently, multi-line array acoustic data are acquired using the established experimental system. Finally, the recorded data are processed and interpreted through velocity analysis and migration imaging. The experimental results demonstrate that the proposed method effectively images the spatial locations and sizes of karst bodies. Furthermore, the imaging performance is influenced by target size, burial depth, and filling medium: larger targets and shallower burial depths yield improved detectability, while variations in filling media are reflected in changes in reflection strength and imaging features. Overall, this study establishes a high-frequency acoustic physical modeling testing method, providing practical support for the optimization and validation of high-resolution detection approaches for small-scale hazard sources under complex conditions.

To evaluate the stability and long-term structural safety of hard rock roadways, this study analyzes the long-term deformation characteristics of surrounding rock induced by TBM excavation and performs high-precision trend predictions. However, traditional prediction methods are often impeded by idealized assumptions and the limitations inherent in single-model frameworks, thereby failing to achieve the high-precision predictions required for surrounding rock deformation under hard rock field conditions. Using the TBM excavation project at the －280 m experimental level of the Beishan underground research laboratory in China as a case study, this research employed real-time in-situ deformation data captured by an embedded multipoint displacement meter system to construct a hybrid prediction model, termed CPO-CLA. This model integrates the crested porcupine optimizer (CPO), convolutional neural network (CNN), long short-term memory (LSTM), and Attention mechanism, utilizing the monitoring data to conduct precise predictions of the long-term deformation of tunnel surrounding rock. The results indicate that during TBM excavation, the internal displacement of the surrounding rock undergoes two distinct phases: an excavation phase and a stable convergence phase, with the maximum cumulative displacement reaching 0.359 8 mm. The CPO-CLA model exhibited superior predictive performance in TBM hard rock tunnel engineering, achieving a mean coefficient of determination R2 of 0.953 on the test set, thereby validating its effectiveness. Comparative analysis against various mainstream meta-heuristic algorithms reveals that the CPO algorithm significantly outperforms them in terms of convergence speed, computational efficiency, and optimization accuracy.

Jiuzhaigou is located in the central segment of China′s North-South Seismic Belt, an area characterized by dense faults and intense tectonic activity, making it a typical high-risk mountainous region susceptible to strong earthquakes. Conducting high-precision back-analysis of historical earthquake-induced landslide (EQIL) hazards and predicting potential EQILs in this region can provide a scientific basis for pre-earthquake risk prevention and post-earthquake emergency response. Using the 2017 Ms 7.0 Jiuzhaigou earthquake as a case study, the spatial patterns of EQILs through detailed field investigations and interpretation of multi-source remote sensing images were analyzed systematically. To address the limitations of the traditional Newmark model in characterizing key parameters, we integrated the spatial heterogeneity of geotechnical strength due to fault perturbations and the topographic amplification effects of ground motion parameters to develop a dual-factor optimized Newmark displacement model. Validation results using actual landslide data from the Jiuzhaigou Ms 7.0 earthquake demonstrated that the accuracy (AUC = 0.827) and spatial rationality of the optimized model significantly surpass those of the traditional method (AUC = 0.738). Moreover, by incorporating ground motion parameters from seven historical earthquakes since the 20th century and the peak ground acceleration data corresponding to a 10% exceedance probability over 50 years, as specified in the fifth-generation ground motion zonation map of China, the back-analysis and prediction of landslide susceptibility under multiple seismic scenarios were conducted. This revealed that the spatial distribution of EQILs is jointly influenced by ground motion, topography, and geology. The comprehensive evaluation method for seismic landslide hazards proposed in this study is designed for the complex environment of mountainous areas prone to strong earthquakes and can provide scientific and technological support for geological disaster risk management and the safety of major engineering projects in Jiuzhaigou and similar regions along the eastern margin of the Qinghai-Tibet Plateau.

To investigate the failure mechanisms of lunar soil slopes under lunar surface conditions and to promote the adaptation of terrestrial shallow mining technologies to the lunar environment, this study systematically analyzes the effects of gravity and Van der Waals forces on slope failure mechanisms through a combination of discrete element numerical simulations and physical bottom friction tests. Based on the two-dimensional particle flow code (PFC2D), a rolling resistance mechanism and van der Waals forces are incorporated into the contact model of lunar soil particles. By assigning differentiated rolling resistance coefficients to particles of different sizes and considering adhesive effects, the particle shape effects and inter-molecular forces are reasonably characterized. A dynamic static combined calibration mechanism ensures the accuracy of the model, enabling numerical simulations of rapid slope excavation processes under different gravity conditions. On this basis, physical validation is conducted using a self-developed experimental platform for mining slope stability under low-gravity lunar surface conditions and Lunar Regolith Simulant. The mutually validated results of numerical simulations and bottom friction tests indicate that without considering factors such as the high vacuum and extreme temperature differences on the lunar surface, the slope exhibits significant subsidence with the failure mode primarily characterized by progressive shallow particle flow under low-gravity lunar surface conditions. In contrast, under terrestrial gravity conditions, the failure is mainly manifested as “tensile-shear” failure. The influence of van der Waals forces on particle motion is gravity-dependent, becoming more pronounced under low-gravity conditions, where it promotes particle motion in the form of “quasi-clusters” and reduces the dispersion effect during motion. The findings of this study can provide a reference for slope stability analysis and disaster prevention in lunar resource extraction.

Landslides are widely observed on various solid celestial bodies in the solar system, the characteristics of which vary markedly under different gravity and geological environments across these bodies. However, a comprehensive review addressing the classification, distribution, triggering mechanisms, and mobility of extraterrestrial landslides remains lacking. This study systematically examines the classification, spatial distribution, triggering factors, and mobility of landslides on various solid celestial bodies. The results indicate that extraterrestrial landslides are diverse, and can be primarily classified as collapse, sliding, flow, spread, creep, and compound types. The distribution of landslides varies significantly among different bodies, primarily influenced by topography, geological processes, and gravity. The main triggering factors for extraterrestrial landslides include gravity, seismic activity, impact events, fluid-solid interactions, thermal stress weathering, and gas sublimation. The study further reveals that changes in gravitational acceleration significantly affect landslide mobility and volume; lower gravitational acceleration increases mobility and volume of landslides. Additionally, landslides on different bodies exhibit a pronounced volume effect that increased landslide volume corresponds to enhanced mobility. The greater the gravity, the stronger the volume effect. The findings of this study provide fundamental insights into the characteristics of extraterrestrial landslides and offer valuable reference for future spacecraft landings and long-term base site selection on extraterrestrial bodies.

The macroscale mechanical properties and seismic wave velocity responses of Martian rocks are fundamental to the design of surface engineering operations and in-situ exploration missions on Mars. However, the small size and irregular morphology of Martian meteorite samples make it difficult to directly obtain their macroscale mechanical properties through traditional laboratory tests. To address this issue, the Martian meteorite NWA 13190 is taken as the research object and a cross-scale prediction approach that integrates microscale mechanical experiments with an accurate grain-based model (AGBM) to determine its macroscale elastic modulus and P-wave velocity is proposed. First, a TESCAN integrated mineral analyzer (TIMA) is employed to characterize the mineral composition, microstructure, and spatial distribution of minerals. Subsequently, nanoindentation and atomic force microscopy (AFM) are used to measure the micromechanical properties of the main rock-forming minerals and interphases. Based on these data, an AGBM incorporating the mineral distribution is constructed, and numerical simulations of uniaxial compression and elastic wave propagation are performed. The results indicate that NWA 13190 is mainly composed of clinopyroxene and maskelynite, with a macroscopic elastic modulus of 29.48 GPa and a P-wave velocity of 2.41 km/s. Compared with traditional macroscale experiments, the proposed approach does not require standard-sized specimens and enables rapid prediction of macroscale mechanical properties and wave velocity under sample-limited conditions. The results provide key mechanical parameters for rover mobility, drilling optimization, and seismic velocity inversion, and support rapid parameter evaluation in early Mars exploration stages.

Supporting the design and performance prediction of lunar surface sampling systems, this study systematically investigates the axial resistance characteristics of coring tubes under direct and rotational penetration modes. Based on the bearing capacity theory of hollow pipe piles, a semi-empirical model for direct penetration is developed that accounts for the influence of wall thickness in small-diameter coring tubes. An experimental platform is established to measure the axial resistance force and sampling performance of coring tubes with varying geometric dimensions during penetration to a depth of 80?mm. Experimental results validate the model and reveal that annular resistance constitutes the dominant component. For rotational penetration, the dependence of the macroscopic friction coefficient on shear rate in the particle-metal interface is introduced. Theoretical and experimental evidence confirms that rotation significantly reduces axial resistance and improves both sampling success rate and sample length. Discrete element simulations using PFC elucidate the microscopic evolution of lunar soil particle flow and soil plug formation during rotational penetration, revealing the key factors governing sampling success. This study provides a theoretical basis and experimental support for structural design, actuator selection, and drilling parameter optimization in lunar surface sampling systems.

The efficient acquisition of lunar samples is the foundation for promoting lunar scientific research and resource utilization, and coring drilling is the core technology to realize deep-depth lunar sampling. Investigating the drilling load characteristics of simulated lunar rock under extreme lunar environment serves as the basis for achieving efficient deep coring. Using simulated lunar rock as the research object, suitable drill bit configurations were optimized. Systematic drilling experiments were conducted under vacuum conditions across a controlled range of environmental temperatures, with a focus on analyzing the evolution characteristics of drilling loads and quantitatively evaluating the sampling rate and the thermal behavior of the drill bit. The results indicate that: (1) cemented carbide octagonal prism drill bits are well suited for coring simulated lunar rock under lunar extreme environment. (2) Lunar environmental temperature significantly affects coring efficiency, with coring rates generally decreasing as temperature increases, and low temperatures being more favorable for obtaining intact cores. (3) Drill temperature rises gradually with sampling time, and higher environmental temperatures accelerate the rate of temperature increase. (4) Under lunar extreme environment, reducing environmental temperature and employing a combined rotation-impact drilling mode are effective strategies for acquiring intact cores and preserving stratigraphic information. The research findings can provide scientific basis and technical support for the optimization of lunar-based drilling and mining equipment and deep drilling and core sampling.

Anisotropy is a fundamental characteristic of the small-strain behavior of unsaturated clay minerals, with its microscopic mechanisms governed by the coupled effects of interparticle hydration and stress levels. To elucidate the multiscale mechanisms through which confining pressure and suction influence the small-strain stiffness of clay minerals, this study employs a mesoscale coarse-grained molecular dynamics (CGMD) approach, calibrated against full-atomistic potential of mean force (PMF) calculations. An interparticle potential function that explicitly accounts for macroscopic relative humidity (RH) is introduced by incorporating an exponentially decaying oscillatory term, enabling the quantitative characterization of the periodic oscillatory decay of interparticle forces arising from the ordering of water molecules. Montmorillonite platelets are idealized as oblate ellipsoidal particles, and the evolution of small-strain elastic anisotropy is systematically investigated under various RH and confining pressure conditions. Mesoscale simulations are performed using the LAMMPS platform to capture the small-strain elastic response of clay minerals, and the simulation results exhibit a consistent trend with experimental data at both macro- and microscopic scales. The evolution of stiffness anisotropy is further analyzed in relation to fabric evolution, elucidating the microscopic mechanisms underlying the effects of pressure and RH. The results indicate that under constant RH, increasing confining pressure enhances small-strain stiffness and anisotropy, with the fabric progressively evolving toward an ordered, transversely isotropic structure characterized by face-to-face particle stacking. Under low confining pressures, an increase in RH leads to a reduction in stiffness, a slight decrease in anisotropy, and a tendency toward fabric loosening, accompanied by reduced stacking density and order. Furthermore, a well-defined linear correlation is observed between the macroscopic anisotropy parameter and the mesoscopic order parameter.

The soil-rock mixture is a composite material consisting of fine-grained soil, rock blocks, pores, and voids. Its macroscopic mechanical properties are closely linked to its internal mesoscale components. This paper focuses on the macroscopic elastic properties of soil-rock mixtures and proposes a stepwise equivalent homogenization prediction method by integrating micro-porosity theory, interface phase theory, and Eshelby′s inclusion theory. The validity of this method is confirmed through numerical tests and laboratory experiments. Furthermore, the paper investigates how the macroscopic elastic modulus of soil-rock mixtures varies with changes in internal mesostructure. The results indicate that the proposed theoretical method effectively predicts the macroscopic elastic modulus and Poisson′s ratio of soil-rock mixtures. When the rock content is below 60%, the difference between the predicted elastic modulus and experimental results is minimal. Under the same rock content, the macroscopic elastic modulus decreases with increasing void content and rises with the inclination angle of the long axis. When the long-axis inclination angle is between 0° and 50°, the macroscopic elastic modulus is positively correlated with the aspect ratio; however, it exhibits a negative correlation at inclination angles ranging from 50° to 90°.

To investigate the heave deformation law of group pile foundations under deep excavation conditions, this study is conducted based on the background of an actual high-speed railway bridge project. A full-scale field model test of group pile foundations with dimensions completely consistent with the engineering prototype is carried out. Through precise monitoring and systematic analysis, the deformation characteristics, force transmission laws, and key influencing factors of group pile foundations under deep excavation conditions are thoroughly revealed. The test results show that soil unloading rebound is the core inducement of heave deformation of pile foundations under deep excavation. When the excavation depth of the soil around the pile foundations reaches 9.5 m, the maximum heave deformation at the pile top is only about 1mm, and the overall deformation amplitude is at a relatively small level. Under symmetric excavation conditions, the horizontal displacement of the pile top shows no significant change, and the stress state remains stable. However, when the asymmetric excavation thickness is 3.5m, the horizontal displacement of the pile top slightly shifts towards the soil-unloading side, with the displacement amplitude ranging between 0.2–0.3 mm and the deformation influence range being limited. The study confirms that the main reason for the small heave deformation of group pile foundations is the limited amplitude of soil unloading rebound deformation. This research achievement can provide important references for the deformation prediction and design optimization of pile foundations in major projects such as high-speed railway bridges under deep excavation conditions. It is clarified that in relevant deformation calculations or numerical simulations, it is crucial to reasonably select the rebound modulus parameter based on the current stress level and unloading state of the unloaded soil, which is the key to ensuring the accuracy of calculation results.

Addressing the subgrade featuring a high-saturation upper layer and a low-saturation lower layer induced by the pot cover effect, this paper simplifies the covering layer as an impervious boundary and the unsaturated subgrade into a pot cover layer and a non-pot cover layer, thereby establishing a one-dimensional transient response analysis model for a double-layer unsaturated soil column. First, the displacement field is decomposed into its static and dynamic components, and the boundary conditions are rendered homogeneous. The characteristic equation is then solved to obtain the system?s eigenvalues and eigenfunctions. Finally, the method of undetermined coefficients and precise time integration method are used to directly provide a semi-analytical solution to the problem in the time domain, which can effectively avoid the numerical instability issues associated with the Laplace method. The correctness of the model and solution in this paper is verified through degeneration. The results of the example calculations show that the pot cover effect markedly alters the pore water pressure response under dynamic loading. As the water content of the pot cover layer increases, both the excess pore water pressure and the solid displacement increase. When the water content is nearly saturated, the peak values of pore pressure can reach 14.5 times the initial water content, respectively. Therefore, in engineering practice, it is necessary to pay attention to the dynamic disasters caused by the pot cover effect.