Rock mass disasters are caused by instability driven by energy within the rock mass. The excavation and unloading disturbance can lead to fractures and instability in the rock mass structure, which is a major cause of dynamic disasters such as water inrush in stopes. To understand the influence of excavation unloading on rock mass structure fractures and to clarify the degradation law of surrounding rock and the mechanism of dynamic disasters like water inrush, this study focuses on the characteristics of rock damage and the evolution of energy under stress-seepage coupling factors. Using the Rock Top multi-field coupling tester, the study investigates the rock damage characteristics and energy evolution under three stress paths: conventional triaxial compression (group C), conventional unloading confining pressure with different initial damage degrees (group W), and cyclic loading and unloading confining pressure (group X) under the influence of stress-seepage coupling. Based on the evolution characteristics of rock elastic strain energy, the stress-strain curve of rock under conventional triaxial compression (group C) is divided into five stages, and the characteristics of U₁, U₃, U_e, U_d and permeability change in each stage are explained in detail (U_e is the elastic strain energy, U_d is the dissipated energy, U₁ is the strain energy of the rock transformed by the positive work done by the axial stress on the rock, and U₃ is the strain energy released by the negative work). During the conventional confining pressure unloading process, the evolution law of U₁ and U₃ is similar to that of group C rock, but the negative growth of U₃ is more significant. The rock input energy gradually shifts from U_e to U_d, and the initial damage degree has no significant influence on the law. During the confining pressure unloading process, the permeability shows a fluctuating upward trend, and the confining pressure is negatively correlated with the permeability. In the process of cyclic loading and unloading confining pressure, the energy evolution law is similar to that of group W rock, with energy accumulation differing only due to time effects. On the whole, regardless of the stress path, the pre-peak rock is dominated by U_e, representing energy storage, while post-peak rock is dominated by energy release and dissipation. Axial stress loading is the main influencing factor for rapid accumulation of U_e, while the change in confining pressure is not enough to cause a large change in U_e. Axial load is the primary factor influencing engineering disasters. Furthermore, there is a significant negative correlation between rock damage variable and confining pressure. The larger the confining pressure is, the smaller the U_e release ratio of rock is, and the smaller the rock damage is. Confining pressure restraint effectively enhances the energy storage capacity of rock and inhibits the dissipation and release of rock energy.

To achieve the scientifically designed gradation composition of a salt rock aggregate base in an inland dry salt lake, this study focused on the salt rock in Lop Nur as the research subject. The analysis examined the particle breakage evolution of a single particle group of salt rock aggregate under different particle sizes and brine contents. A gradation transition model for salt rock aggregate under complex gradation was constructed, and a gradation composition design method for salt rock aggregate base was proposed. The rationality of this design method was verified, and the engineering properties of the rock salt aggregate were compared under different gradations and water loss rates. The results demonstrated that all particle groups of the salt rock aggregate experienced breakage during compaction. The gradation of uniformly graded salt rock aggregate tended to stabilize with increasing compaction work. The presence of brine reduced the particle breakage rate of uniformly graded salt rock aggregate. The Weibull distribution effectively characterized the particle breakage distribution characteristics of the salt rock aggregate. The recommended gradation composition design method of salt rock aggregate base successfully deduced the gradation characteristics of salt rock aggregate base and realized the gradation correction considering the influence of brine. Salt crystallization of brine among salt rock particles was conducive to promoting the strength formation of salt rock aggregate base. The unconfined compressive strength of the salt rock aggregate with a water loss rate of 75% reached 4.1 MPa, indicating its suitability for road base engineering in dry salt lake areas.

Due to the complexity of the pore size distribution (PSD), the variation pattern of the pore structure for clay during the drying process is not clear, which leads to an inaccurate calculation of the soil-water characteristic curve (SWCC) based on the pore distribution model. To address this issue, a study was conducted to quantitatively analyze the PSD of remodeled clay with the single or double pore structure during the drying process based on the shrinkage test and mercury intrusion porosimetry test. The results revealed that there were translational and scaling transformations of the PSDs during the drying process. The t-distribution and double t-distribution functions were proposed to describe the PSDs of clay. The degrees of freedom, the peaks and the pore diameters corresponding to the PSD peaks were extracted as characteristic parameters to characterize the variation of PSDs. Good linear relationships between the characteristic parameters and the void ratio of remodeled clay were observed. Based on these findings, the relationship of water content-void ratio-pore size distribution was further established, and a framework for calculating the SWCC of remolded clay considering the variation of pore structure was proposed. Finally, the accuracy of the proposed calculation method was verified by comparing with the experimentally measured SWCC.

The waste soil generated during shield tunnel construction poses a challenge in terms of stacking, transportation, and treatment. One promising approach is the use of magnesium oxide (MgO) for the solidification treatment of waste soil, as it is abundant in raw materials, has low production energy consumption, and is eco-friendly. The limit moisture content w, unconfined compressive strength qu and modulus of elasticity E₅₀ of MgO solidified and carbonized mucky waste soil were studied by changing the MgO content am, curing age T, and carbonization time H. The solidification and carbonization mechanism of MgO-treated mucky waste soil was discussed in combination with the microstructure and the change rule of mineral composition. The results demonstrate that MgO solidification and carbonization have a significant reinforcing effect on the soil. The reinforcement effect initially increases and then stabilizes with increasing am and T, while it shows an initial increase followed by a decrease with H. Carbonization for 4 hours reduces the soil plasticity index (IP) by more than 57% under different am and T conditions, leading to a significant reduction in soil plasticity. The qu of solidified and carbonized soils reaches a peak value at H of 4 hours, with values up to 1.4 MPa, which is 220%–350% higher than the strength before carbonization. The effect of solidification and carbonization reaction on the increase in E₅₀ of the soil mass is greatly influenced by am. When am exceeds 9%, the E50 increase of the sample carbonized for 4 hours exceeds 500%. During the process of MgO solidification and carbonization, hydration products and carbonization products are continuously generated and developed. They form a network and flower-like microstructure, filling the pores between soil particles, enhancing cementation between soil particles, and densifying the soil structure. The research provides insights into the efficient and eco-friendly treatment and reuse of mucky waste soil produced by earth pressure shield in the Yangtze River Delta.

The particle breakage, deformation, and strength properties of calcareous sand are related to the drainage conditions during shearing. However, the effect of undrained shear processes on the particle breakage and mechanical properties of calcareous sand are rarely considered in the current studies. A series of consolidated drained and undrained triaxial shear tests is conducted on calcareous sand with various initial relative densities under different effective confining pressures to investigate the effects of drainage conditions on particle breakage and mechanical properties during shearing. The results show that the particle breakage rate in the drained shear test is higher than that in the undrained shear test under the same effective confining pressure. The stress–strain curves of calcareous sand exhibit the behavior of strain softening during both drained and undrained shear, and its dilatancy behavior is influenced by the initial relative density and the effective confining pressure. The critical state of calcareous sand is independent of its initial state but related to the drainage conditions during shearing. Both the critical stress ratio and the phase change stress ratio in the drained shear test are larger than those in the undrained shear test. The peak effective friction angle of calcareous sand decreases with the increase of initial relative density, effective confining pressure, and percentage of particle breakage while the critical effective friction angle is not affected by these three factors. Both of these effective friction angles are related to the drainage conditions during shearing. The peak effective friction angle and the critical effective friction angle in the drainage shear test are greater than those in the undrained shear test. The above results indicate that the particle breakage, deformation, and strength properties of calcareous sand are significantly correlated with the drainage conditions during shearing.

To investigate the mechanical properties and failure characteristics of bedding coal under different stress paths, mechanical tests were conducted using the MTS816 rock mechanics testing system. Coal samples with bedding angles of 0°, 30°, 45°, 60°, and 90° were subjected to tests under three stress paths: conventional triaxial loading, increasing axial pressure unloading confining pressure, and constant axial pressure unloading confining pressure. The study analyzed the influence of stress paths and bedding angles on the strength, deformation, and failure characteristics of the coal samples. The results indicate the following: Under the path of conventional triaxial loading, the stress-strain curves of the coal samples show a nearly linear relationship before reaching the peak point, followed by a rapid drop in stress after reaching the peak. Under the path of increasing axial pressure unloading confining pressure, the axial strain increment ratio exhibits a linear increasing trend as the unloading ratio increases. The circumferential strain increment ratio and volumetric strain increment ratio display a three-stage change characteristic, involving low-speed growth, rapid growth, and stable growth. Under the path of constant axial pressure unloading confining pressure, the axial strain increment ratio, circumferential strain increment ratio, and volumetric strain increment ratio exhibit a two-stage change characteristic, involving low-speed growth and rapid growth. The peak strength and axial peak strain of the coal samples exhibit a V-shaped trend with increasing bedding angle under different stress paths. They initially decrease and then increase, reaching the maximum value at 0° and the minimum value at 60°. As the unloading ratio increases, the deformation modulus of the coal sample initially stabilizes and then rapidly deteriorates. The Poisson’s ratio first slowly increases and then exponentially increases. The critical unloading ratio initially increases and then decreases with increasing bedding angle. When the bedding angle is the same, the critical unloading ratio under the path of increasing axial pressure unloading confining pressure is lower than that under the path of constant axial pressure unloading confining pressure. Under the path of conventional triaxial loading, the coal sample undergoes brittle shear failure. However, under the paths of increasing axial pressure unloading confining pressure and constant axial pressure unloading confining pressure, the coal sample exhibits a mixed tensile-shear failure mode. When the bedding angle is 60°, the angle of the main shear fracture surface of the coal sample is almost consistent with the bedding angle.

To study the dynamic propagation characteristics of mode I crack in infilled jointed rock masses under impact load, dynamic impact compression tests were implemented by a split Hopkinson pressure bar (SHPB) system and a crack propagation measurement device. The single cleavage triangle (SCT) specimens with the joints filled by gypsum, cement, and marble glue were adopted. The dynamic propagation processes and impact failure modes of the crack were analyzed, and the evolution laws of stress intensity factor and energy release rate during the dynamic propagation of mode I crack were studied by the experimental-numerical method. The results show that there are three main failure modes of the infilled jointed rock masses: the prefabricated crack extends and penetrates the whole specimen, the infilled joint fails after the crack penetration, and the infilled joint fails first and then blocks the crack penetration. The failure of the filling body in the joint is related to the strength and cementation force of the filling body, as well as the strain rate of the dynamic load. The crack propagation speed has an oscillatory growth from the crack initiation point and reaches the maximum at a certain position before the crack penetrates the infilled joint, while the stress intensity factor and energy release rate reach the maximum near the joint. The stiffness degradation of the infilled joint inhibits the crack propagation and causes a sharp increase in the energy release rate. The difference in lithological combinations aggravates the material property mismatch of the rock mass specimens, resulting in different decreases of stress intensity factor and energy release rate as the crack passes through the joint.

In the process of unidirectional freezing, the generation and development of segregating ice is an important factor affecting the structural characteristics of frozen and thawed soil. Three unidirectional freezing boundary conditions were selected, i.e., cooling rate (from 0.5 ℃/s to 0.005 ℃/s), cold temperature (from –30 ℃ to –70 ℃), and water replenishment (no water replenishment, constant pressure water replenishment) to explore their influence on the development of segregating ice. To facilitate the measurement of segregating ice, an independent meso-measurement system has been developed using optical microscope digital photography. This system enables in-situ and non-contact measurement of segregating ice cracks. The experimental results demonstrate the following findings: (i) The distribution of segregating ice is not only influenced by temperature gradients and warm end replenishment conditions, but also by the cooling rate at the cold end of the unidirectional freezing process. (ii) The width of the segregating ice in the frozen area is more significantly affected by the movement rate of the frozen front than by the temperature gradient. (iii) During the freezing process, the width of the frozen ice exhibits an exponential relationship with the movement rate of the 0 ℃ line. Based on this characteristic, an empirical formula is proposed to predict the crack width of segregating ice in the frozen zone. This formula can be used as a reference for evaluating unilateral frost heave failure in practical engineering construction, particularly under conditions of varying cooling rates.

Aiming at the problem of one-dimensional transport of heavy metal contaminants (HMCs) in a triple-layer composite liner composed of geomembrane (GM), geosynthetic clay liner (GCL) and compacted clay liner (CCL) under the consideration of temperature change, the governing equations for thermal conduction and HMCs transport are developed based on the relevant assumptions, and a corresponding theoretical model is established. The theoretical model constructed in this study is solved numerically by the finite difference. Subsequently, a comparative analysis with the experimental measurements, the analytical solution calculations and other numerical solution calculations is performed to validly verify the reasonableness of this model. Finally, the effects of different factors on the transport laws are analyzed and discussed using Cd²⁺ as an example. The results show that an increase in the upper temperature increases the transport flux and bottom concentration of Cd²⁺ in the composite liner, but decreases its upper concentration. The thermal diffusion effect on the transport behaviors becomes significant with an increasing in Soret coefficient ST, and the defined breakthrough times tb are 37.9, 37.2, 36.4, 31.2 and 26.5 a for S_T of 0.001, 0.005, 0.01, 0.05 and 0.1 K^–1 in this order. The increase in the maximum adsorption capacities of GCL and CCL leads to the approximately linear growth in tb, and under a certain leachate head h_b, the tb almost increases linearly with the increase of GCL thickness and CCL thickness. Furthermore, as h_b increases from 0.5 m to 1.0 m, the t_b reduces by an average of 8.33 a. In engineering practice, the adsorption performance and thickness of both GCL and CCL can be combined to design a composite liner, where the influence of temperature variation on barrier effectiveness should be incorporated.

In order to predict the diffusion process of bentonite colloids in the fractures of surrounding rocks in the deep geological repository of high-level radioactive waste in Beishan, Gansu, a diffusion model that integrates the self-weight of bentonite colloid particles and hydration force is proposed. The effects of sodium ion concentration, hydration force, self-weight of colloid particles, and volume fraction of montmorillonite on the diffusion process and diffusion coefficient of bentonite colloids were investigated. The results show that both the diffusion rate and diffusion distance of bentonite colloids decrease with the increase of sodium ion concentration. The greater the self-weight of colloidal particles, the more significant their impact on diffusion. As the diffusion proceeds, the influence of hydration force on diffusion gradually decreases, while the influence of van der Waals force and diffusion double-layer force gradually increases, and in general, the diffusion coefficient of bentonite colloids decreases first and then increases. When the volume fraction of montmorillonite is small (φ <0.45), the diffusion coefficient generally increases with the increase of sodium ion concentration; when the volume fraction of montmorillonite is large (φ >0.45), the influence of sodium ion concentration on the diffusion coefficient is relatively small.

In dredging projects, the water content of dredged mud is typically very high. The conventional method of dewatering and curing into mud cake has relatively low treatment efficiency. To address this issue, a study was conducted on the integrated dewatering-curing process of Taihu dredged mud. Ordinary Portland cement and calcium sulfoaluminate cement were chosen as curing materials, along with flocculants and plate and frame press filter technology. The study analyzed the dewatering performance of the slurry, the pattern of curing effect changes, and the loss of curing materials through specific resistance tests and curing tests. The pathway of curing material loss and its impact on the dewatering performance of the mud were discussed based on the fundamental property changes observed during the integrated process experiments. The results demonstrated that the integrated dewatering-curing process can enhance the dewatering characteristics by improving the particle size and compressibility of the dredged mud. The loss of curing material during the process was found to be less than 9%. The dewatering mud cake exhibited improved properties, resulting in effective curing effects. In practical engineering applications, the use of the integrated dewatering-curing process can enhance the efficiency of mud treatment.

The soft interlayer, often considered the “weak link” of slopes, poses a significant threat to slope stability. This study focuses on the Permian carbonaceous shale soft interlayer commonly found in Southwest China. The creep characteristics of the soft interlayer were investigated, and a graded shear creep test was conducted in addition to conventional shear tests to analyze the shear deformation behavior of the soft interlayer comprehensively. The long-term strength of the soft interlayer was determined using the steady-state creep rate method. Building upon the Riemann-Liouville fractional order integral theory and statistical damage theory, an improved model based on the traditional Nishihara model was developed. The accuracy of the model was verified using the adaptive differential evolution algorithm in combination with the weak interlayer shear creep test curve, followed by a parameter sensitivity analysis. The results demonstrate that the improved model adequately describes the three stages of creep in the weak interlayer. The creep curve is influenced by the differential order γ , the shape parameter m, and the proportional parameter F₀. Parameter m reflects the brittle characteristics of the soft interlayer, while parameter F₀ characterizes its physical and mechanical strength. The research results can provide a theoretical basis for disaster prevention monitoring and stability analysis of slopes with weak interlayer.

By conducting undrained cyclic triaxial tests on fibre-reinforced very loose and loose saturated sand, we investigated the build-up of excess pore pressure and the flow liquefaction responses. The test results show that unreinforced very loose and loose saturated sand has a high potential for liquefaction, with flow liquefaction occurring in all unreinforced samples under undrained cyclic loading. The presence of fibre reinforcement has a positive impact on the resistance to flow liquefaction of sand. Fibres provide both a densifying effect and a confining effect to the sand skeleton. However, the confining effect of fibres depends on the loading path imposed on the samples and the deformation mode of the samples. The presence of fibres alters the evolution law of the residual excess pore pressure in saturated sand. When fibres impose a strong confining effect on the sand skeleton, the evolution of residual excess pore pressure along with the normalized loading cycles follows a curve with an ‘inverted L’ shape, being significantly different from an ‘S’ shape curve which is followed by the unreinforced sand. Under the two-way symmetrical and one-way cyclic loading, the significant fibre stress contribution is mobilized, leading to the effective stress of the sand skeleton being much greater than 0 after the 100% build-up of excess pore pressure. As a result, the strength loss of the reinforced sample remains below 11% and thus the fibres prevent liquefaction from developing.

This study aims to investigate the quantitative relationship between resistivity and the physical and mechanical properties of soil in different types of herbaceous slopes in the alpine arid and semi-arid loess area. The research is conducted in the self-built test area of Changlinggou Basin in Xining Basin. Five types of slopes, including Elymus nutans Griseb., Elymus sibiricus Linn., Agropyron trachycaulum Linn. Gaertn., Festuca arundinacea Schreb., and bare slopes are selected as the research objects. These slopes have been planted for 3 years. The study compares the effects of different herbaceous roots on the physical and mechanical properties of the soil by conducting tests of soil density and water content, and direct shear test on the soils with and without root systems. Based on these tests, a quantitative relationship between the physical and mechanical properties of different slope soils and resistivity data is established using 2D electrical resistivity tomography. The results show that: (1) Compared with the bare slope without planting, the maximum increase of soil moisture content in the upper layer (0–10 cm) of the Elymus sibiricus Linn. slope is 26.53%. The average soil density of the upper layer (0–10 cm) of the Festuca arundinacea Schreb. slope was 18.30% lower than that of the bare slope. The maximum added value of soil cohesion in the upper layer (0–10 cm) of the Elymus nutans Griseb. slope is 2.75 times that of the bare slope. (2) The resistivity characteristics of five types of slopes are affected by root distribution and slope position factors, and the resistivity value decreases with the increase of depth. The soil resistivity value of the four herbaceous slopes is larger than that of the bare slope at 0–20 cm, which is the approximately range of root distribution. (3) There are fitting equations between the physical and mechanical properties and resistivity data of five kinds of slope soils (with correlation coefficients R² ranging from 0.48 to 0.77), and the Pearson correlation analysis shows that the cohesion c value of the slope soil has the highest correlation with resistivity, with an R² value of 0.765. The results of this study demonstrate that 2D resistivity tomography technology can reflect the physical and mechanical properties of slope soil, as well as the distribution characteristics of plant roots. This provides a theoretical basis and practical guidance for effectively preventing and controlling soil erosion, shallow landslides, and other disasters in the study area and its surrounding areas.

In the challenging and perilous mountainous regions of Southwest China, there are numerous layered and fractured rock slopes with varying inclinations. These slopes are prone to disasters such as collapses and landslides during earthquakes, posing a serious threat to the ongoing construction of the Sichuan-Xizang Railway. To address this issue, large-scale shaking table model tests were conducted to study the dynamic response, failure modes of instability, and energy transfer characteristics of dip and anti-dip layered slopes under strong earthquake conditions. The test results reveal that the anti-seismic performance of anti-dip slopes is significantly better than that of dip slopes. The failure mode of dip slopes primarily involves tensile cracking, shearing, uplift, and slip failure. On the other hand, the failure mode of anti-dip slopes mainly consists of tensile, bending, tilting, and collapsing failure. The natural vibration frequency of anti-dip slopes is higher compared to dip slopes. As the earthquake magnitude increases, the natural frequency of dip slopes gradually decreases. However, the natural frequency of anti-dip slopes exhibits repeated oscillations within the range of seismic amplitudes of from 0.4g to 0.7g. Dip slopes exhibit clear “elevation amplification effect” and “tend-surface effect,” while anti-dip slopes demonstrate the “elevation amplification effect.” Furthermore, the internal acceleration response is greater than that of the slope surface. Marginal spectrum identification indicates that the most significant change in peak of marginal spectrum amplitude (PMSA) for dip slopes occurs at the upper part of the slope waist. This suggests that the energy loss of seismic waves near this position is the largest, indicating the formation of a sliding failure surface near the upper part of the slope waist. For anti-dip slopes, the PMSA decreases most significantly at the slope shoulder, indicating severe damage and a propensity for local collapse in this area. The analysis results are in good agreement with the experimental observations, providing further insights into the dynamic response and instability failure modes of different structural types of layered slopes under strong earthquakes. These findings serve as a basis for ensuring the safe construction of the Sichuan-Xizang Railway.

The dynamic constitutive models based on viscous, elastic, and plastic elements often suffer from poor prediction performance and fail to fully capture the viscous, elastic, and plastic characteristics of cohesive soil. To address these limitations, a viscoelastic-plastic constitutive model for cohesive soil is proposed in this study by introducing a triggered viscoplastic element (symbolized as Ψ) and considering residual deformation as a starting point. The model takes into account the phenomena of vibration stability and vibration decay and is validated through dynamic triaxial shear tests. This dynamic constitutive model not only describes the development pattern of residual strain in cohesive soil under dynamic loads but also provides reasonable predictions for dynamic strain development. The results indicate that the viscosity coefficient of the Ψ element decays as the vibration period increases, and this attenuation is closely related to the moisture content under dynamic loading conditions. The optimal moisture content serves as an important parameter that influences both vibration stability and vibration decay. When the moisture content is less than the optimal moisture content, the deformation of the sample exhibits vibration stability, and the change of the viscosity coefficient can be ignored. When the moisture content is greater than the optimal moisture content, the deformation of the sample exhibits vibration decay, and the change of the viscosity coefficient cannot be neglected.

Stiffened deep cement mixing (SDCM) pile are gaining popularity in civil and architectural engineering due to their combination of core pile advantages, such as high axial load transfer ability, and deep mixing column advantages, such as high side friction. SDCM piles offer high construction efficiency, high bearing capacity, and lower costs. However, the existing calculation methods for determining their bearing capacity often differ significantly from actual test results due to a lack of unified understanding regarding their load transfer mechanism. To address this, full-scale field tests of SDCM piles embedded in silt were conducted to study the compressive bearing characteristics and load transfer mechanism. Ordinary cement and gypsum-slag soil hardening agent were both used as the binder materials in SDCM pile. The pile load-displacement curves were measured, and the ultimate bearing capacity of a single SDCM pile under compression was analyzed. The influence of binder materials was also checked. Coring tests were conducted to obtain its unconfined compressive strength (UCS). The discreteness of UCS between the field mixing cemented soil and the laboratory test were also analyzed. A three-dimensional elastoplastic finite element numerical model considering the interfaces of core pile-cemented soil and cemented soil-in-situ soils was established. The distribution of axial force along pile shaft and the shear stress between contact surfaces under different loads applied to the pile head were explored. The load transfer mechanism was analyzed and the higher bearing capacity compared with bored piles were discussed. The results show that the ultimate compressive bearing capacity of the SDCM pile in silt is larger than 1.5 times the sum of the compressive bearing capacity of the pure deep mixing pile and the single core pile. As the end resistance takes effect and increases, the shear deformation between the core pile and the cemented soil at the pile tip will increase rapidly due to the axial compression of the cemented soil. Thus, this position is prone to shear failure. Compared with traditional bored piles, the improvement of the bearing capacity the SDCM pile is mainly due to the interface improvement caused by solidification.

Due to historical variations in stress and sedimentation, geotechnical materials exhibit strong spatial variability. This means that the distribution and properties of geotechnical types vary across different sites and even within different locations of the same site. Existing random field models struggle to accurately capture this complex spatial variability and often lack verification with in-situ test data. To address these limitations, this paper focuses on studying the spatial variabilities of marine clay parameters in the three Nordic countries using the open database 304dB developed by the Engineering Practice of Risk Assessment and Management TC-304 in the International Society of Soil Mechanics and Geotechnical Engineering (ISSMGE). The paper analyzes and compares the differences and similarities in statistical characteristic parameters of marine clay along depth variations in the three Nordic countries. It also investigates the physical mechanisms of mutual influence between various parameters and clarifies the spatial variability laws of each parameter. Through trend analysis, fluctuation analysis, and correlation analysis, the study reveals that the mean value, standard deviation, and fluctuation scale of marine clay parameters in the three Nordic countries are non-constant along the depth. The mean value increases linearly with depth, while the standard deviation shows an approximate quadratic function variation trend along the depth. The correlation function is dependent on distance and location, but does not converge uniformly with increasing distance. Based on stratification correlation analysis of comprehensive samples, a stratification non-homogeneous random field model of marine clay parameters is established. In this model, the mean value of the random field follows a linear function along the depth, while the standard deviation is a spatially varying random field with a quadratic function trend. Parameters exhibit different mean values, initial standard deviation values, and fluctuation scales at different stratification locations. Each layer displays distinct characteristics of discontinuous variation. Compared to homogeneous random field models and non-homogeneous field models that only consider linear increases in mean value along the depth, the stratification non-homogeneous random field model comprehensively describes the complex spatial variability of mean value, standard deviation, and correlation of marine clay parameters along the depth. It also effectively captures the stratification characteristics of discontinuous variation.

Accurate prediction of tunneling-induced ground surface settlement is crucial for ensuring safe construction and decision-making in tunneling projects. In this study, a physics-informed neural network (PINN) model is established for predicting shield tunneling-induced stratum deformation. This model is constructed by incorporating the relationship between tunnel convergence deformation and tunneling position into a deep neural network (DNN) framework. Considering the geological characteristics of multiple strata, a multi-physics-informed neural network (MPINN) model is proposed to represent the physical information of different strata in a unified framework. The results show that the MPINN model can highly reproduce the results by the finite difference method, and can accurately predict the tunneling-induced ground surface settlements considering the complex geological information of the composite strata. Due to the integrated physical mechanism, the MPINN model is applicable to the problem of tunnel-induced ground surface settlement, and it can be employed to predict the tunneling-induced ground surface settlement under different geological and geometric conditions. Based on the measured data, the proposed MPINN model accurately predicts the ground surface settlement curve of the monitored cross-section, thus it can provide a reference for the prediction and early warning of ground surface settlement during tunneling process.

In the field of overhanging rock prevention and control, the stability calculations have traditionally used simplified two-dimensional profiles as the calculation model. However, the irregular shape of overhanging rocks in nature cannot be accurately represented by this simplified model, leading to limitations in stress analysis. To address this, a three-dimensional calculation method for overhanging rock stability was developed based on limit equilibrium theory and previous research. The proposed method focuses on the stability against overturning of overhanging rocks controlled by the tensile strength of the trailing edge crack. A three-dimensional calculation formula was derived, taking into account the tension resistance, water pressure, and moment of the trailing edge rock. The formula was implemented using numerical integration and spatial geometry methods, providing a comprehensive approach to analyzing the stability of overhanging rock. To validate the proposed method, an application was conducted using the Diaozui overhanging rock in the Qutangxia area of the Three Gorges Reservoir. Numerical analysis was performed to verify the results. By analyzing the stability of different forms of overhanging rock in three dimensions, the relationship between the three-dimensional stability calculation results and the traditional two-dimensional stability analysis was explored. The findings revealed that the shape of overhanging rock significantly impacts the stability calculation results. It was concluded that three-dimensional calculations provide more accurate and practical results compared to the traditional two-dimensional approach.

The stability of perilous rock bank slopes in the fluctuation belt of the Three Gorges Reservoir Area is greatly affected by the deterioration of the rock mass caused by periodic water level fluctuations. A study was conducted using field research, geological survey data, and numerical simulation with the universal distinct element code (UDEC) to investigate the impact of degradation zone morphology on the stability of nearly horizontal layered high steep perilous rock bank slopes. The research findings indicate that the rock mass in the fluctuation belt of the Wushan section of the Three Gorges Reservoir Area exhibits severe degradation in nearly horizontal layered perilous rock bank slopes. Different degradation zones exhibit distinct degradation morphologies, including tightly layered, loosely fragmented, dissolution cavity, and compression fractured zones. Perilous rock bank slopes with the first type of degradation zone morphology demonstrate good stability, with minimal displacement and sliding failure as the primary instability mode. The second type of degradation zone morphology causes the perilous rock body of the bank slope to shift inward and then collapse outward as the support strength of the rock mass weakens. The third type of degradation zone morphology leads to significant displacement towards the outside of the slope, with toppling failure as the instability mode. The stability of perilous rock bank slopes with the fourth type of degradation zone morphology is primarily influenced by the mechanical properties of the compressive fracture zone, which is prone to rotational sliding failure along the cutting surface of the fracture zone. By implementing prevention and reinforcement measures on the perilous rock bank slopes in the different types of deterioration zones mentioned above, the deformation and displacement of the perilous rock masses have been effectively controlled to varying degrees.

This paper presents a theoretical prediction model for the surface movement duration in coal mining, which takes into account various factors such as coal seam mining height, average mining depth, loose layer thickness, bedrock layer thickness, and mining speed. The model is based on the improved Knothe time model and incorporates the definition of surface movement duration. Additionally, a method for determining the model parameters using the probability integration method is provided. To validate the rationality and accuracy of the prediction model, monitoring data from 24 deep working faces are utilized. The results demonstrate that the predicted surface movement duration aligns well with the monitoring results from the working faces. The mean absolute error is only 38 days, the root mean square error is only 47 days, and the mean absolute percentage error is only 9%. These values indicate a significantly lower prediction error compared to existing empirical models. The accuracy of the surface movement duration prediction model is confirmed. The study further reveals that the duration is influenced by coal seam mining height, average mining depth, loose layer thickness, bedrock layer thickness, and mining speed. Specifically, it increases nonlinearly with coal seam mining height, linearly with average mining depth, loose layer thickness, and bedrock layer thickness, but decreases nonlinearly with mining speed. This research provides theoretical guidance for evaluating the stability of surface movement and deformation in coal mining and formulating scientifically sound mining plans.

The study of the degradation mechanism of freeze-thaw damaged rock holds significant theoretical importance in understanding freeze-thaw disasters, predicting disasters, and designing tunnel protection systems in cold regions. Based on the volume expansion theory, this research establishes a correlation between irreversible volume increase and the number of freeze-thaw cycles, and also deduces the law of radial heat transfer for cylindrical samples during freeze-thaw cycles. Considering the freeze-thaw damage process of saturated samples, a model of rock freeze-thaw damage based on discrete elements is developed. The physical and mechanical properties of sandstone with different freeze-thaw cycles are tested to validate the model, using stress-strain curves and uniaxial compressive strength. Building upon this, the growth and distribution of cracks in rock samples during freeze-thaw cycles are analyzed, and the crack growth process under coupled freeze-thaw-stress conditions is studied. The research findings indicate that as the number of freeze-thaw cycles increases, the development of cracks undergoes three stages: slow, fast, and then steady. The number of cracks increases radially from the inside to the outside of the sample. Approximately 80% of the frost heave cracks are distributed in the circular column area 10–25 mm away from the sample’s axis. When the number of freeze-thaw cycles is less than 80, the increase in the number of cracks follows an exponential function relationship. However, when the number of freeze-thaw cycles exceeds 80, the number of cracks increase logarithmically with their distance from the center of the circle. During the freeze-thaw cycle, the damage in the sample primarily occurs through tensile failure, and the freeze-thaw damage process of the rock is influenced by the initial pore structure.

Single rough-walled fracture and surrounding rock matrix are the basic units that compose the discrete fracture network, so it is of great significance to study the fluid flow behaviors in it. A series of numerical simulations by directly solving the Navier- Stokes equation were carried out to study the influence of surface roughness, matching degree and matrix permeability on non-Darcian flow in three-dimensional single rough-walled fracture. The results review that the Forchheimer equation can accurately characterize the nonlinear relationship between the flow rate and pressure gradient in single fracture in fracture-matrix model. The increase of surface roughness and the degree of mismatch aggravates the inhomogeneity of aperture distribution, increases the flow resistance of the fracture and facilitates the non-Darcian flow. By contrast, the permeable matrix enhances the flow through the fracture, and the flow rate through the rough single fracture can be increased by up to 14%, which inhibits the non-Darcian flow. The influence level of matrix permeability on the growth of fracture flow capacity is positively correlated with surface roughness and degree of mismatch.

In this study, the rock fracture propagation is simulated based on the ordinary state-based peridynamics, and a numerical model of rock hydraulic fracturing is proposed by means of real-time tracking of newly generated fracture and applying pressure to simulating the interaction between fracturing fluid and fracture surface. According to the digital image processing technology, the Zhang-Suen thinning algorithm is applied to extracting the skeleton of hydraulic fracture network, and a quantitative method of hydraulic fracture network is presented by using the statistical method to calculate the morphological parameters. Finally, the process of hydraulic fracture propagation and the evolution of fracture network morphological parameters are studied considering the effects of loading rate, in situ stress condition and elastic modulus. The results show that when the loading rate is small, the main fracture expands towards the direction of the larger in situ stress, and the fracture branch is not obvious. Increasing the loading rate can increase the average width and density of fractures, promote the opening degree and number of fractures, enhance the complexity of fracture network, and improve its permeability. When the horizontal and vertical in situ stresses are the same, the major fractures intersect. With the increase of vertical in situ stress, the horizontal fractures are restrained, the major fracture propagates along the vertical direction, and the total length and density of fractures increase. The increase of elastic modulus of rock mass can reduce the propagation of fracture branches and simplify the fracture network.

This paper investigates the mechanism of submarine pipeline penetration into calcareous sand by using centrifuge testing and discrete element modeling. The results indicate that the pipeline penetration resistance shows a linearly increase trend with the pipeline embedment, and its value is approximately equal to the product of pipeline-soil contact width and the cone penetration resistance obtained from the cone penetration test (CPT). When the pipeline embedment is small, the penetration resistance is almost unaffected by particle strength due to the fact that the soil deformation is dominated by the particle rearrangement. When the pipeline embedment is large, the penetration resistance decreases with decreasing particle strength and increasing particle breakage. The mechanism of pipeline penetration into calcareous sand exhibits a typical punching shear failure. The soil deformation primarily occurs at the bottom of the pipeline, and the teardrop-shaped deformation region gradually shrinks with increasing particle breakage. The particle breakage develops radially away from the bottom of the pipeline, where most successive particle breakages tend to occur near the pipeline, while a few individual breakages are more common in regions far from the pipeline. The particle breakage results in the release of stress concentration at the bottom of the pipeline. The more the particles break, the more the stress releases, and the more obvious the resulting decrease of penetration resistance.

Accurately detecting the structure of top coal is crucial for achieving intelligent fully-mechanized caving mining. However, the complex structure of coal seams in China, often consisting of multiple layers of separated gangue, can significantly impact the effectiveness of fully-mechanized caving mining. To address this challenge, this paper proposes a precise detection method for top coal structure based on multi-frequency radar fusion. This method aims to improve the detection accuracy of the shallow part within the radar antenna’s detection depth and interpret the structural information inside the top coal. The main research steps are as follows: Firstly, preprocessing and spatial alignment of radar data of different frequencies are carried out to establish the spatial correspondence between radar data of different frequencies. Secondly, a sliding window and wavelet transform weighted fusion method is employed to process the multi-frequency radar data. The time-varying weight value of each frequency signal is determined based on the energy proportion of each segment wavelet signal in the window. Additionally, an edge detection algorithm is introduced to enhance the fusion efficiency of the wavelet transform to the radar data, thereby achieving effective fusion of the multi-frequency radar data. Finally, taking into account the differences in dielectric constants between coal, gangue, and rock, as well as the attenuation characteristics of electromagnetic wave propagation, an internal echo intensity model of top coal is established. The interface information between coal, gangue, and rock inside the top coal is calculated using a stratified identification method, enabling the inverse interpretation of the internal structure of top coal, including the thickness of top coal, the thickness and number of gangue layers, and the spacing between gangue layers. The test results demonstrate that the proposed method can effectively integrate radar data of different frequencies and accurately detect the internal structural characteristics of top coal. Moreover, the detection errors of the thickness of top coal, the thickness of gangue, and the spacing between gangue layers are all less than 10%. This method enables the accurate detection of top coal structure, providing theoretical and technical support for the intelligent fully-mechanized caving mining.