In low-temperature environments, the physical and mechanical properties of rocks, as well as their engineering behavior, differ significantly from those at ambient temperature, primarily due to water-ice phase transitions. These differences become more pronounced as the temperature decreases. Considering industry-specific low-temperature classification standards and the environmental conditions of geotechnical engineering, a refined low-temperature zoning framework tailored to geomechanics is proposed, defining the threshold for “deep low temperatures” and further subdividing it into “extreme low temperatures” and “ultra-low temperatures.” Based on findings from laboratory experiments, theoretical analyses, and numerical simulations, this study provides a systematic review of the physical and mechanical properties of rocks under deep low-temperature, with a particular focus on the temperature-dependent evolution of key parameters such as porosity, elastic wave velocity, thermal conductivity, elastic modulus, and mechanical strength. Furthermore, by employing the thermo-hydro-mechanical (THM) coupling models, the mechanisms by which frost heave effects, thermal stress distribution, and water migration contribute to rock damage are analyzed. Numerical simulations reveal the coupled evolution characteristics of the temperature, stress, and seepage fields, as well as their underlying roles in the accumulation and progression of rock damage. Additionally, key scientific and technological challenges associated with deep low-temperature rock mechanics are examined in the context of engineering applications, such as underground energy storage, liquid nitrogen-based waterless fracturing, polar infrastructure, and deep-space resource extraction. Finally, based on current theoretical advancements, technological developments, and engineering demands, several future research directions in rock mechanics under deep low-temperature conditions are proposed. These include investigations into the micro-scale phase transition dynamics and multi-scale damage mechanisms of rocks in deep low temperatures, the development of non-equilibrium multi-field coupling theoretical frameworks, and the spatiotemporal prediction of long-term rock performance under deep low-temperature conditions.

Based on the characteristics of extensive areas and complex rock structures in open-pit mining, this study investigates the rock structure, disaster characteristics, and disaster prediction model of the slopes in the Fushun west open pit mine. Considering the relationship between the orientation of rock layers, the mining site, the distribution of structural planes, and the degree of rock weathering, the rock mass structure of the slopes was classified into four categories: anti-dip layered structure, bedding structure, fractured rock mass structure, and soil-like rock mass structure. A survey and statistical analysis of slope disasters that occurred in the Fushun west open pit mine over the past decades were conducted. Slope failures were categorized into three types: sliding, toppling, and collapse. Among these, sliding disasters accounted for 65.04% of the total surveyed incidents, toppling disasters accounted for 10.57%, and collapse disasters accounted for 24.39%. A general model for disaster prediction in mining areas was established based on an understanding of the rock mass structure and disaster characteristics of the slopes in the Fushun west open pit mine. The model utilized the Verhulst inverse function curve to characterize the displacement-time relationship of monitoring points, with model parameters iteratively solved using the gradient descent method. Displacement rates of 10 mm/h and 5 mm/h at monitoring points were established as criteria for the near-failure states of soft and hard rock slopes, respectively. The applicability and accuracy of the established prediction model were verified through typical disaster cases. Furthermore, it is emphasized that slope disaster prediction should adhere to function approximation methodologies, where the completeness of data directly correlates with the prediction accuracy of disaster occurrence timing. The research findings provide valuable reference and guidance for the identification, monitoring, early warning, and safety prevention of slope disasters in open-pit mines.

 During the dynamic failure of coal and rock, a significant number of fragments are ejected, and the ejection distance and kinetic energy of these fragments can more intuitively reflect the intensity of the specimen?s failure. This paper proposes a method for measuring the ejection kinetic energy of coal and rock fragments, with its feasibility verified through numerical simulation examples. Experimental research is conducted on the ejection characteristics of fragments from different types of rocks. Based on these findings, a classification method for burst liability is proposed, utilizing the burst kinetic energy index. Furthermore, the influence of loading stiffness on the ejection characteristics of fragments and the burst kinetic energy index of coal is analyzed. The results indicate that the ejection characteristics of coal and rock specimens vary significantly among different lithologies. The ejection mass proportion and distance of fragments from granite and basalt are notably greater than those from sandstone, marble, and coal, which exhibit lower strength. The stronger the burst liability of the specimen, the greater the ejection distance and kinetic energy of the fragments. The ejection kinetic energy of the fragments shows a positive power function relationship with uniaxial compressive strength, and a positive linear relationship with both the burst energy index and the residual elastic energy index. The recommended ranges for the burst kinetic energy index are as follows: for coal with no burst liability, less than 30 J/m3; for weak burst liability, 30 to 300 J/m3; and for strong burst liability, greater than 300 J/m3. As the stiffness ratio of the testing machine to the specimen decreases, the energy supplied by the testing machine to the coal specimen increases, resulting in an increase in both the ejection distance and kinetic energy of the fragments after failure. The burst kinetic energy index exhibits a positive power function relationship with the stiffness ratio. The proposed method for measuring the ejection kinetic energy of specimen fragments and the burst kinetic energy index can effectively evaluate the burst liability and damage intensity of coal specimens.

To address the challenges posed by complex regional stress and the maintenance of surrounding rock in soft rock roadways subjected to strong dynamic pressure crushing during excavation, this study focuses on the 1570 track stone gate of Daniuchang Coal Mine in Guizhou Province as the engineering context. A comprehensive research approach was employed, utilizing numerical simulations, theoretical analyses, and on-site industrial tests. Through on-site investigations and data monitoring, we analyzed the large deformation of the surrounding rock at Shimen on the 1570 track and the failure characteristics of the supporting components. The poor self-stability of the surrounding rock was investigated using water immersion tests (combined with XRD analysis) and loose ring tests. Numerical simulations were conducted to elucidate the stress distribution patterns during the excavation of the 1570 track stone gate, revealing its deformation and failure mechanisms. We specifically proposed a full-space collaborative support technology for the reconstructed multi-bearing structure. The ultimate bearing stress of the most critical section of the concrete steel arch frame was derived through theoretical analysis, confirming that the constrained steel pipe filling structure could effectively limit the significant structural movements induced by mining activities. The stress distribution and deformation control effects of the surrounding rock in the reconstructed multi-bearing structure were analyzed through numerical simulations, clarifying the control principles underlying the full-space cooperative support technology. By constructing a three-layer high-strength load-bearing structure, we integrated the shallow and deep surrounding rocks into a cohesive high-strength anchor solid load-bearing system. This approach harnesses the surrounding rock′s inherent load-bearing capacity and enhances the overall anti-deformation capability of the surrounding rock, thereby establishing a full-space three-dimensional support system that ensures roadway stability. Subsequent industrial tests conducted underground demonstrated that the full-space collaborative support technology for multi-bearing structures significantly mitigates deformation in roadways facing strong dynamic pressure crushing and soft surrounding rock. Compared to the original support system, the convergence of the top and bottom slabs of the roadway, as well as the two sides, was reduced by 91.67% and 88.33%, respectively. Additionally, this approach led to savings in roadway maintenance costs, providing an effective solution for managing surrounding rock in soft rock roadways subjected to strong dynamic pressure crushing.

Existing backfill technologies prove insufficient to ensure coordinated water conservation and overburden control requirements for high-productivity longwall mining beneath aquifers in western Chinese coal fields, primarily attributed to compromised extraction efficiency and scarcity of conventional backfill materials. This necessitates innovative advances in backfill theory and technology to achieve non-interference between mining and backfilling, as well as secure mining operations under aquifers in one unified process. This research proposes a method of gangue grouting and interval backfilling in post-mining space. A gangue fluidised grouting diffusion simulation system is developed, and the diffusion characteristics and laws of gangue slurry in the mining space are tested. A numerical model of gangue grouting and interval backfilling in post-mining space is established, and the deformation and stress evolution laws of key aquiclude strata at different equivalent backfilling rates are studied, revealing the control mechanism of gangue grouting interval backfilling for rock layers under aquifers in mining space. The research results demonstrate that the method of gangue grouting and interval backfilling in post-mining space and its key parameters are proposed, with the equivalent backfilling rate defined to characterise the volume of grouted filling. The gangue slurry exhibits significant lateral and longitudinal extension during its spread in the mining space. The lateral spreading range of the slurry shows an approximately linear growth trend from top to bottom, with a final distribution shape resembling a circular table. As grouting pressure increases, both the lateral and longitudinal extension of the gangue slurry are gradually enhanced. The lateral diffusion diameter decreases with increasing slurry concentration. The subsidence reduction rate of key aquiclude strata increases exponentially as the equivalent backfilling rate rises. An equivalent backfilling ratio of at least 70% is required to achieve effective control of the watertight critical layer. The gangue slurry and broken rock body together form a load-bearing assembly with significantly enhanced mechanical properties. This load-bearing combination achieves control of the rock layer in the mining space under the aquifer by limiting the deformation of the waterproofing key layer, reducing stress concentration in the waterproofing key layer, and decreasing the continuity in the separation area. This investigation establishes theoretical foundations for both ecologically sustainable disposal of coal-based solids and reliable water-preserved mining in arid western regions.

Maintaining surrounding rock thermal insulation is crucial for preventing frost damage in cold-region tunnel engineering. Active thermal balance preservation in surrounding rock holds critical importance for frost damage prevention in cold-region tunnels. This study proposes the approach of frost damage prevention by phase change energy storage practively. The temperature control system for tunnel surrounding rocks was established using phase change materials (PCMs), developing phase-field model for cold-storage heat-retention PCMs and deriving mathematical equations for solid-liquid phase transition alongside an optimal phase change temperature calculation formula. Following the principles of maximum latent heat and prolonged phase change duration, PCM material suitable for cold-region tunnel engineering was developed. Experimental investigations were conducted to evaluate the thermal properties, durability, and temperature regulation performance of cold-storage heat-retention PCMs under freeze-thaw conditions. Tests revealed that: (1) The developed PCMs, composed of decanoic acid and decanol in a mass ratio of 55.39∶107.38 with latent heat of 231.17 J/g, exhibiting superior heat storage performance among low-temperature phase change materials. (2) DSC and temperature scanning tests on cold-storage heat-retention PCMs revealed single-peak exothermic/endothermic curves during freeze-thaw cycles, confirming stable eutectic formation and consistent thermal storage performance. The prolonged heat storage/release phases demonstrated significant peak-shaving and valley-filling effects, effectively mitigating frost heave and thawing-induced damage in cold region engineering. (3) After 300 phase-change cycles, the FTIR spectral profiles and DSC curves remained consistent. The developed PCMs demonstrate maximum phase transition temperature deviation of 0.08 ℃, latent heat variation ＜5%, and super-cooling degree ＜5 ℃, confirming excellent thermal cycling stability and durability. (4) The temperature control efficacy of PCMs is influenced by temperature gradient. Ensuring the full utilization of phase change materials is the key to maximizing its phase change potential in freeze-thaw environments. Therefore, appropriate PCMs thickness selection based on local climate conditions proves essential for temperature regulation. The relevant research results provide valuable theoretical insights and practical guidance for the development of frost damage prevention and thermal insulation technologies in cold region tunnel engineering.

To investigate the influence of the number of fractures on the strength of rock before and after grouting, as well as the patterns of crack propagation, an experimental study was conducted on the mechanical properties of sandstone containing varying numbers of fractures under both ungrouted and grouted conditions. The study employed XTDIC (digital image correlation) and acoustic emission systems to analyze crack propagation patterns from both macroscopic and microscopic perspectives. The experimental results revealed the following: (1) As the number of fractures increased, the duration of the compaction stage in the stress-strain curve decreased, leading to an earlier onset of crack development and propagation. The strength weakening coefficient exhibited a power function growth trend in relation to the number of fractures, resulting in an average compressive strength reduction of 15.82% to 53.32%. Under a 1:1 water-cement ratio slurry, the strength recovery coefficient demonstrated an exponential decrease as the number of fractures increased, improving by 6.76% to 29.27% compared to the ungrouted state, achieving 60.34% to 89.88% of the original rock strength. (2) The number of fractures had a significant impact on crack initiation stress, which increased after grouting. The ratio of crack initiation stress to peak stress before and after grouting decreased with an increasing number of fractures, exhibiting a downward-opening quadratic function relationship. (3) Crack propagation patterns under different fracture numbers showed certain similarities before and after grouting. Cracks predominantly originated from the tips of fractures and interconnected pre-existing fissures, leading to rock bridge penetration and primarily resulting in tensile failure. (4) The acoustic emission ringing count and cumulative ringing count significantly increased with the number of fractures. Grouting could only partially enhance the overall integrity of the rock and alleviate stress concentration at the tips, but it failed to effectively suppress crack propagation and interaction. (5) Theoretical analysis indicated that the stress intensity factor after grouting was lower than that before grouting, suggesting a reduction in stress at the tips of the fractures post-grouting, thereby enhancing the rock′s strength. This finding was corroborated through numerical simulations.

Grouting as a main technical means for stability control of fractured surrounding rock, its reinforcement effect is controlled by many factors. To investigate the effect of inclination angle and rock matrix on grouting reinforcement, this paper carried out uniaxial compression tests of grouted coal, mudstone and sandstone specimens with different crack inclination angles (? = 0°, 15°, 30°, 45°, 60°). Combined with the digital image correlation (DIC) and acoustic emission (AE) technology, the evolution characteristics of their mechanical properties were investigated. Test results showed that: (1) the peak strength showed a tendency of decreasing and then increasing with the increase of inclination angle for different rock specimen; the damage mode of the grouted fractured coal and mudstone specimens shifts from split tensile to shear failure along the fracture, whereas the sandstone specimens were dominated by interfacial shear damage. (2) The DIC results showed that the maximum principal strains of different specimens first increase and then decrease as fracture inclination angle increases, which the mudstone specimens had the smallest value, and the coal specimens had the smallest changes in the strain field. (3) The acoustic emission characteristics showed that the percentage of tensile microcracks decreased with the increase of inclination angle. Combined with the analysis of acoustic emission b-value, the mudstone and sandstone specimens had the smallest and highest degree of failure, respectively. Finally, the slurry-rock interface correlation coefficient k was proposed to analyze the mechanical property evolution mechanism of the grouted fractured rock mass. Results indicated the inclination angle and rock matrix jointly controlled the mechanical behavior of the grouted fractured rock mass through the rock strength and slurry-rock interface characteristics. The above study provides theoretical and experimental basis for the design of grouting reinforcement and stability analysis of surrounding rock in deep tunnel.

Based on uniaxial compression experiments of red sandstone and employing the digital speckle correlation method, this study investigates the variation trends of strain increment under uniaxial loading conditions through physical instability characterization of rock material failure, establishing a short-term imminent prediction method for red sandstone failure under uniaxial loading based on strain increment. The main conclusions are as follows：(1) Through physical instability analysis of rock material failure, a stress-strain increment expression for the complete rock loading failure process was established, categorizing the strain increment during rock loading failure into three distinct stages. (2) The threshold value for angular variation between deformation increment d? and stress increment d? was determined based on Poisson?s ratio parameter, with three statistical indicators of quantity, maximum value, and average value of measurement points exceeding the threshold all exhibiting fluctuating variation patterns, indicating the cyclic adjustment state of rock specimens during loading. (3) A temporal correlation between critical change node time and total failure time was established, achieving multi-stage prediction of rock loading failure time. (4) Delineated action boundary lines drawn based on the position, magnitude, and direction of threshold-exceeding measurement points at different times consistently appeared in proximity to rock failure cracks, demonstrating partial reflection of the development state of rock fracture propagation. (5) An energy prediction formula with adjustment coefficient K was developed, where K values range from 1.5 to 2.5.

Under the influence of natural geological forces, concealed karst fissures are primarily subjected to compressive-shear stress states. To establish an effective tensile-shear fracturing criterion, this study first identifies the critical conditions for the fracture of water-pressurized concealed karst fissures using the maximum tangential stress (MTS) criterion. Subsequently, a shear fracture criterion is formulated based on the Mohr-Coulomb strength theory. By referencing the dimensional form of the improved maximum energy release rate criterion and integrating the aforementioned tensile-shear fracture criteria, a composite fracture criterion (M criterion) is developed based on KIC and KIIC for I–II type fracturing. This criterion refines the MTS criterion when the II-type component predominates, addressing the limitation of the MTS criterion that considers only the tangential stress ?θ and uses KIC as the crack initiation threshold. It incorporates the shear stress component ?rθ and KIIC as well. Comparative analyses of M-criteria with different power exponents were conducted using the displacement discontinuity boundary element method, based on geological stress, rock parameters from Liangwangshan Tunnel tests, and field investigation results of karst fissures. Results validate that the proposed composite fracture criterion outperforms the MTS criterion in predicting critical conditions for fracture propagation, making it more applicable to water inrush problems involving karst fissure propagation under natural hydraulic pressure where compressive-shear stress is dominant.

The statistical damage constitutive model of rocks and the evaluation methods for brittleness are prominent research topics in the field of rock mechanics. This paper analyzes the nonlinear deformation characteristics during the initial compaction stage of rocks, identifying the full crack compaction point as the critical juncture. First, a constitutive model for the compaction stage is developed based on the changes in tangent modulus and logistic distribution characteristics. Subsequently, drawing on the principles of continuous damage mechanics and statistical damage, we assume that the strength of microelements adheres to the logistic distribution and the Mohr-Coulomb criterion, thereby establishing a damage constitutive model that captures the deformation characteristics post-compaction. Furthermore, a novel brittleness evaluation index is proposed, reflecting the entire damage evolution characteristics. Finally, the proposed constitutive model and brittleness index are validated using uniaxial and conventional triaxial compression test data from glutenite, granodiorite, red sandstone, quartzite, marble, and Maharashtra sandstone. The findings indicate that: (1) The segmented constitutive model based on logistic distribution accurately simulates the complete stress-strain process of various rock types under uniaxial and conventional triaxial compression, effectively describing both peak strength and peak strain of the samples. (2) The speed of damage evolution is inversely proportional to confining pressures; thus, increasing confining pressure can suppress damage development, enhance ductility, and reduce brittleness. (3) The parameters m and f0 influence the degree and length of concavity on the compaction stage curve, while parameters M and F0 affect the degree of brittle failure and peak strength. Collectively, these four model parameters govern the deformation characteristics, strength properties, and brittleness of the rock, ultimately shaping the theoretical constitutive relation curve. (4) The brittleness evaluation index, which comprehensively considers the pre-peak damage degree, peak strain, and post-peak damage evolution speed of rocks, demonstrates rationality, and the feasibility of this new index is corroborated through experimental results across six rock types under varying confining pressures. This research offers valuable insights for constructing brittleness indexes grounded in the rock damage constitutive model, thereby enhancing the analysis and evaluation of rock brittleness.

The stress intensity factors (SIFs) are critical parameters for evaluating crack propagation behaviour and rock mass stability. In order to improve the accuracy of SIFs determination based on Williams series and digital image correlation (DIC), this study proposes a regional search method combining displacement residuals and the Williams series term -1 to locate crack tip. Numerical simulations were conducted to systematically analyze the influence of calculation region parameters and the number of expansion terms. The variation of SIFs in mode I fractures were calculated and analyzed for polymethyl methacrylate (PMMA) and granite specimens with prefabricated cracks under three-point bending. The results indicate: (1) This method remedies the deficiency of the -1 term in the Williams series, which is only applicable to straight crack propagation, and resolves the issue of local optimal solutions encountered when using displacement residuals alone. (2) For SIF calculations, the recommended angular range for the sector region is 120°–170°. The inner radius should be 0.2 times the prefabricated crack length. The outer radius should be 1 to 2 times the prefabricated crack length, and the maximum expansion order should increase with expansion of the calculation regions. (3) In mode I rock fracture, tortuous crack propagation can be simplified to as straight crack propagation for analysis without significantly affecting SIF results.

The development of deep coal resources is of great strategic significance to ensure national energy security. However, the coal-rock dynamic disaster caused by intense engineering disturbance in deep environment has become a key bottleneck restricting the safe mining of coal resources. Accurate prediction and assessment of coal impact failure intensity becomes crucial for secure resource extraction. Therefore, in this paper, the dynamic impact test of coal was carried out by using the split Hopkinson pressure bar (SHPB) test system, and the damage-energy co-evolution characteristics were obtained. The generalized energy storage performance index k1 and the generalized energy dissipation performance index k2 were defined, and the response mechanism of strain rate to energy storage and dissipation performance of coal was revealed. Combined with the macro and micro failure characteristics, the coal impact failure intensity was discussed, and the dynamic failure intensity evaluation standard was established. The results show that the damage-energy co-evolution law of coal presents a significant strain rate effect. At the same time, the increase of strain rate enhances the energy storage performance and dissipation performance of coal. The coal impact failure intensity can be comprehensively characterized by the fragmentation and ejection degree of coal. Based on the variation of k1 value, the ejection degree of coal fragments can be scientifically divided into four grades: no ejection phenomenon, slight ejection, medium ejection and severe ejection. The degree of coal crushing can be scientifically divided into three grades: slight crushing, medium crushing and severe crushing according to the variation law of k2 value. These findings provide theoretical support and reference for the prediction and prevention of coal-rock dynamic disasters in the process of deep coal mining disturbance.

Numerous indoor tests and engineering applications have confirmed the superiority of prefabricated horizontal drains (PHDs) combined with vacuum preloading in the treatment of dredged sludge yards. However, existing consolidation theories for PHDs-treated dredged slurry currently do not account for the effects of well resistance. This study, based on Gibson′s large strain consolidation theory, incorporates the well resistance effect of PHDs and introduces the nonlinear compressibility and permeability of dredged sludge to establish a consolidation model for treating dredged sludge yards using PHDs in conjunction with vacuum preloading. Solutions for the proposed consolidation model are derived and validated through comparative analysis with existing self-weight consolidation models for ideal PHD configurations and laboratory test results. Furthermore, the influence of well resistance effects on consolidation behavior is systematically investigated. The results indicate that well resistance effects slow down the dissipation rate of excess pore water pressure, consolidation rate, and settlement deformation; however, this retardation progressively diminishes with decreasing well resistance. The magnitude of well resistance is influenced by the installation length of PHDs, the permeability coefficient, the laying ratio of PHDs, and the height of the sludge. Optimizing the layout of PHDs enhances the consolidation efficiency of dredged sludge. Prioritizing the alignment of PHDs along shorter repository dimensions effectively mitigates the impacts of well resistance on consolidation processes. When the laying ratio (?) remains below 40%, increasing ? improves consolidation rates through enhanced drainage capacity. Beyond this threshold, however, the implementation of multi-layer PHDs becomes essential to achieve further efficiency gains.

 To investigate the effects of variable amplitude impact loading on straight-wall-top-arch double tunnels, a large-scale model of high-strength concrete tunnels was constructed. A self-developed pendulum impact system, capable of applying biaxial stresses, was utilized to conduct the impact tests. A super-dynamic data acquisition system was employed to record the impact waves and three-dimensional strains, while digital image correlation (DIC) was used to analyze the surface strains and displacement fields. This approach allowed for a comprehensive examination of the mutation characteristics of double tunnels subjected to pendulum impacts. The experimental results yielded several key findings: (1) The frequency of the shock wave generated by the pendulum ranged from 100 to 200 Hz, exhibiting a wave curve characterized by a peak incremental stage, an oscillatory decay stage, and a stable stage, indicating a variable amplitude shock wave with amplitude attenuation. The frequency decay amplitude increased from 9.30% to 43.88% under multiple impacts. (2) Five symmetrical cracks were observed in the spandrel and foot of the double tunnels, with a wide and deep crack at the inter-cavern arch foot manifesting as an upward concavity. The damage pattern was primarily influenced by the first wave peak of the impact force, leading to an increase in the width of the crack at the inter-cavern arch foot by nearly six times under multiple impacts. (3) The predominant strain type was tensile strain, with a peak axial strain of approximately 10 400×10－6 observed at the inner arch foot, a peak radial strain of about 10 600×10－6 at the inter-cavern arch foot, and a peak circumferential strain of roughly 24 800×10－6 at the outer arch spandrel. Under multiple impacts, the strain increased by approximately 25 times in the axial direction and five times in the radial direction. (4) Vertical strain concentration zones first appeared in the inter-cavern arch foot within 350×10－6. Cracks in the inter-cavern arch foot developed from the two inner arch feet, with strain values stabilizing in the range of 0.002 to 0.005. Shear strain concentration zones were identified in the outer spandrel and inter-cavern arch foot, exhibiting opposite strain behaviors on the left and right sides. The vertical strain peak at the inter-cavern arch foot increased by 42.98%. Considering the crack width and three-dimensional strain data, it was concluded that the inter-cavern arch foot represents the weakest point of the double tunnels under variable amplitude impacts, necessitating enhanced monitoring and support in this area.

 Coarse-grained soils are susceptible to particle breakage under high stress, which leads to changes in soil gradation and affects their stiffness and deformation characteristics. This study investigates the impact of particle breakage on the stiffness and deformation of coarse-grained soils by analyzing their stress-strain behavior across different gradations. Based on the particle breakage law identified through experiments, we propose evolution equations for the isotropic compression line and the critical state line. The breakage ratio within the yield function is treated as a constitutive variable, integrated with the consistency condition, to account for the additional volumetric strain resulting from particle breakage. Utilizing non-orthogonal plasticity theory, we establish the relationship between the particle breakage ratio and the dilatancy parameter through a state variable, which determines the direction of plastic flow under particle breakage conditions. Finally, we develop a non-orthogonal elastoplastic constitutive model for coarse-grained soils to characterize the effects of particle breakage. The validity of this model is assessed using conventional triaxial drainage test data from Changhe rockfill and Cambria sand. The results indicate that the proposed model accurately reflects the transformation of volumetric strain in coarse-grained soils from dilatancy to contractancy as confining pressure increases from low to high, demonstrating enhanced predictive capability under high-stress conditions.

Soil typically exhibits a layered distribution due to long-term sedimentation and geological tectonic activities. The seismic response characteristics of pipe piles embedded in such stratified soil are highly complex, particularly regarding the vertical seismic response of friction-type hollow pipe piles, which warrants further investigation. This paper presents a semi-analytical solution for the dynamic responses of a floating tubular pile in layered soil subjected to time-harmonic seismic P-waves. The solution accounts for the dynamic interactions among the soil surrounding the pile, the pipe pile itself, and the soil beneath the pile, as well as the effects of soil stratification properties. The pile is modeled as an elastic hollow pipe structure, with the soil within its vertical projection area treated as a soil column, while the surrounding soil and the soil column are modeled as a multilayered continuum. Utilizing Hamilton?s variational principle, the equations of motion for the pile and the soil column, along with the pile-soil continuity conditions, are derived. The separation of variables technique and an iterative method are employed to solve these equations of motion for the pile-soil system, incorporating the pile-soil boundary and continuity conditions. This results in a frequency-domain semi-analytical solution for the kinematic responses of the pile-soil system to seismic P-waves. The proposed solution is validated through comparison with existing solutions. Additionally, numerical analyses are conducted to investigate the seismic pile-soil interaction effects across various material and geometric parameters. The results indicate that the layered nature of the soil surrounding the pile and the supporting conditions at the pile base significantly influence the seismic response of the pile to P-waves. Notably, the seismic response of friction-type piles in layered soils under P-waves differs substantially from that of end-bearing piles in homogeneous soils. Furthermore, existing solutions for homogeneous soil or end-bearing piles can be derived through parameter degradation of the developed solution. Additionally, when the inner diameter of the pipe pile exceeds 0.2 m, variations in its size significantly impact the seismic response of the pile-soil system under P-waves; conversely, when the inner diameter is 0.2 m or less, tubular piles exhibit seismic response characteristics comparable to those of solid piles with the same outer radius.

ey soils are widely distributed in thermal-related geotechnical engineering projects, and their consolidation behavior under non-isothermal conditions significantly influences the long-term stability of engineering structures. Additionally, clays commonly contain bound water, which occupies a portion of the pore space and is incapable of free seepage. In this context, the effective void ratio is introduced to characterize the pore characteristics of saturated clay, and a one-dimensional model of nonlinear thermal consolidation under thermal-mechanical loading is developed. This model first accounts for the impact of temperature variation on the compressibility and permeability of saturated clay. To address the pore water migration caused by the temperature gradient, the thermal-osmosis effect is considered to more accurately reflect the seepage properties. Furthermore, the mechanisms of conduction, convection, and thermo-mechanical dispersion are integrated to investigate the heat transfer process. By employing semi-permeable and semi-adiabatic boundary conditions that closely resemble engineering realities, the coupled control equations and numerical solutions for the current model are derived, and their accuracy is verified through degradation analysis and case studies. Subsequently, a parameter sensitivity analysis is conducted to explore the influence of critical parameters on consolidation performance, revealing the coupling mechanisms between nonlinear consolidation and heat transfer. The results indicate that the presence of semi-adiabatic boundaries significantly alters the temperature distribution within the clay layer, which in turn affects permeability at different depths. Moreover, an increase in the effective void ratio can facilitate the heat transfer process, leading to higher final excess pore water pressure and increased final settlement. The inclusion of thermal-osmosis slows down pore water dissipation and exacerbates soil swelling phenomena. Factors such as improved drainage boundaries, shorter heating durations, fewer loading frequencies, or greater temperature gradients contribute to faster consolidation.

To investigate the coupling mechanisms of fracture strength, size effect, and strain rate effect in rockfill particles under seismic loading, single-particle strength crushing tests were conducted on Dalian limestone using a self-developed TPWS–800 medium-strain-rate loading apparatus. The particle sizes ranged from 60 to 300 mm, with displacement loading rates of 0.01, 0.1, 1 and 10 mm/s. The experimental results revealed that the characteristic strength of larger particles increased more significantly than that of smaller particles, indicating enhanced strength rate effects in larger particles. Conversely, higher strain rates resulted in a weakening of the size effect. Based on the generalized weakest-link Weibull model, a power function was employed to characterize the sparsity of spatial microcrack distributions within the particles. The fitting of particle strengths under different loading rates demonstrated significantly better performance compared to models assuming uniform crack distributions. Furthermore, the crack distribution exponent decreased with increasing loading rates, indicating that higher loading rates caused “effective cracks” to become progressively sparser. This phenomenon corresponds to the strain rate dependence of particle strength.