In order to study the energy absorption characteristics and dynamic response rule of constant resistance and large deformation with negative Poisson’s ratio (NPR) anchor cable under the action of earthquake, the physical model test on the tunnel passing through a fault supported by common anchor cable and NPR anchor cable was carried out by using the shaking table test. The dynamic response rule of tunnel structure under different surrounding rock conditions and supported by different anchor cables under the action of earthquake was compared and analyzed. The results show that the damage degree of tunnel structure supported by NPR cable is significantly improved compared with that supported by common cable under the same seismic wave. This suggests that NPR cable has good energy absorption characteristics and can provide effective support for tunnel structure under earthquake. By comparing and analyzing the time-history curves of axial force of common cable and NPR cable, it is evident that under the action of seismic waves, the common cable will break and the axial force will drop to zero, while the high constant resistance of NPR cable can continue to provide effective support. By analyzing the dynamic response of acceleration, strain and earth pressure at each measuring point of the tunnel structure, it can be seen that the dynamic response of the tunnel fault area is more obvious, and the tunnel structure fails in the sequence of arch spandrel→haunch→crown under the action of earthquake. This research achievement provides a theoretical reference for support strategies in tunnel engineering.

Due to rainfall, the soil-rock differential weathering interface of spherical weathered granite soil slopes is prone to evolve into a dominant seepage channel and undergo seepage suffosion, which accelerates the deformation and instability of these slopes. However, little research has been carried out on the characteristics of seepage suffosion and the migration of fine particles. Based on the unsaturated seepage theory of porous media, a numerical calculation framework is established to accurately describe the seepage suffosion process at the soil-rock interface, considering the coupling relationship between the fine particle migration, suffosion initiation response and unsaturated seepage. The finite element method is used to construct a seepage suffosion model for unsaturated granite residual soil under the effect of dominant flow. Based on the seepage suffosion process of homogeneous soil columns, the suffosion characteristics of dominant flow under three typical soil-rock interface burial states are systematically investigated. The results show that the soil-rock interface and the matrix permeability of spherical weathered granite soil slopes are highly variable, with the wetting front forming a downward depression infiltration funnel, and the degree of depression of the wetting front becomes more pronounced as rainfall continues. The degree of fine particle loss is related to the burial state of the soil-rock interface, in which the dominant flow potential suffosion of the under-filled soil condition is the most significant, and even excess pore water pressure occurs at the interface, which is the most unfavorable to the stability of this type of slope. The research results can provide a scientific basis for accurately evaluating the stability of spherical weathered granite soil slopes under rainfall conditions.

In order to accurately analyze the internal force and deformation of pile under the combined horizontal dynamic load (H(t)) and torsional vibration (T(t)) on the top of the pile, a simplified analytical model of H(t)-T(t) loaded pile in layered foundation is established based on the Pasternak model, considering the interaction of multidirectional loads. The numerical solutions of the internal forces and displacements of the pile are derived by using the finite beam element method, and the results are compared with the existing theoretical solutions, model tests and finite element simulations. Parametric analysis shows that: (1) Compared with the calculation results of Winkler model, the horizontal displacement at the top of the pile and the maximum bending moment of the pile are reduced by 11.8% and 10.5%, respectively, after considering the shear effect of the soil. (2) Increasing the dimensionless frequency of the external load reduces the horizontal displacement and bending moment of the pile, and also reduces the H(t)-T(t) coupling stiffness. (3) In the layered foundation, the surface soil has the greatest influence on the internal force and displacement of the pile, and there is a critical influence depth of the surface soil. The critical influence thickness of the surface hard soil is 3.5–6.5 times that of the surface soft soil. (4) The beam element model reduces the number of element divisions and calculation time, which can effectively improve the calculation efficiency.

The research focused on exploring the characteristics of fault stick-slip instability and the combined multi-source precursor characteristics of acoustic emission (AE) and charge signals through bidirectional shear friction experiments on syenogranite with faults of different dip angles under lateral pressures of 5, 15, 25 MPa. The mechanical behavior of the fault and time-frequency characteristics of AE and charge induction signals were observed and analyzed. The key findings and observations are summarized as follows. (1) Lateral pressure and fault dip were found to change the stick-slip characteristics, affecting the induced charge and the magnitude of AE event. Increasing the lateral pressure led to gradual increase in the proportions of induced charge and charge accumulation rate in the meta-instability stage and stick-slip instability stage gradually increase. Compared with 56° fault, the amplitude based statistical index b-value of 45° fault was smaller, and the proportion of large-scale rupture was larger. (2) The fractal dimension of amplitude was observed to reflect differences in energy released by the fault. Phased response characteristics of the frequency characteristics of AE and charge induction signals were identified as effective means to discern the evolution process of fault stick-slip at the laboratory scale. A sharp increase in the main frequency amplitude was recognized as one of the precursor characteristics. The AE and charge induction parameters (energy, fractal dimension and spectral amplitude) in the stage from meta-instability to stick-slip instability showed distinct “sudden increase” characteristics. (3) There was a good correspondence between the energy of AE and charge induction signal and the stress drop, although not entirely synchronous. AE signal responded to stick-slip instability before charge induction. It was emphasized that combining AE and charge induction signal characteristics is essential for achieving mutual complementation and verification of the acoustic-charge binary signal.

 In order to investigate the energy attenuation of microseismic signal in the "three-zone" structure of goaf, a similar model test of the overburden of goaf is proposed to collect the artificially excited microseismic signals propagated through the structure of goaf. The relationship between the central frequency and energy of the modal components of the microseismic signal via variational mode decomposition (VMD) is analysed. The optimum number of modal components of the microseismic signal is determined according to the central frequency method, and the energy of each component is calculated for the under-decomposition, optimum decomposition and over-decomposition states of the microseismic signal. The relationship between the energy of each modal component and the central frequency distribution is fitted for the optimum decomposition state of the signal under each source, and the energy of each modal component is analysed for different propagation states of the microseismic signal in the "three-zone" structure. The effect of each structural layer on the energy of the microseismic signal under different propagation states of the "three-zone" structure is analyzed. The results of the study show that: (1) The number of effective modes of the artificially excited vibration signal in the VMD process ranges from 6 to 11, and the energy of the microseismic signal varies significantly with the number of modes. (2) The power function can be used to fit the modal energy versus frequency of the microseismic signal, and the fitting state is good (the coefficient of determination is greater than 0.9), in which the low-frequency modal component contains nearly 50% of the total energy of the signal. The Gaussian function can be used to fit the distribution performance of the energy of each component of the source in the frequency domain, and the fitting state is good and shows the Gaussian single-peak characteristic. (3) The microseismic signal traverses through the "three-zone" structure of goaf, and the energy of the microseismic signal decreases as the distance between the source location and the sensor increases. The collapse zone has a significant attenuating effect on the signal compared to the fracture zone and the bending zone. The energy of the microseismic signal does not change as it passes through the "three-zone" structure of goaf.

Due to its safety, stability, low cost and easy installation, anchor plate support structure has been widely used in the slope that needs to be reinforced. However, currently in the design process of anchor plate support structure, there is no mature calculation method for the size of anchor plate, resulting in overly conservative design. To address this issue, we propose using the limit equilibrium method in combination with log-spiral slip surface to calculate the active earth pressure in unsaturated soils. Based on the internal balance of the soil, the tensile force required to bear for each layer of anchor plate is calculated, and the calculation method for the size of the anchor plate is obtained. The minimum design length of the free section of the anchor plate is obtained according to the shape of the sliding surface. The calculation results of active earth pressure are compared with the existing literature, and it is found that the change trend of active earth pressure coefficient is consistent with the existing conclusions. The impacts of rainfall and earthquake conditions on the size of anchor plate are analyzed, and the results show that low rainfall intensity has a negligible effect on the size of anchor plate. However, when considering both strong rainfall and earthquake, the required anchor plate size can be significantly increased, with a maximum of 136.71%. The analysis results can provide reference for determining the size of frame anchor plates.

A three-dimensional rotational failure mechanism of embankment was built based on the upper limit analysis theorem. Drawing on the shear strength theory of Bishop unsaturated soil and considering the spatial distribution of matrix suction inside the unsaturated embankment and its change with the groundwater level, the energy conservation equation encompassing the external force work rate and the internal energy dissipation rate of the embankment was established. An efficient genetic algorithm was developed to search for the least upper-bound value of unsaturated soil embankment. By degrading the unsaturated soil embankment failure mode into a slope failure mode and comparing critical values with existing unsaturated soil slope stability calculations, the correctness of the proposed upper-bound values and the accuracy of the genetic search algorithm were verified. Furthermore, the influence of the pore size distribution, matrix suction, the inverse of the air entry value, embankment inclination angle and effective internal friction angle on the three-dimensional stability of the embankment was systematically studied. The results demonstrated that the stability of unsaturated soil embankment depends not only on the properties of soil but also on the pore size parameters and the inverse of the air entry value. Additionally, the fluctuation of matric suction resulting from changes in groundwater levels significantly impacts the stability of unsaturated soil embankments. These findings offer an important theoretical basis for granular analysis of embankment stability and the design of ultimate fill height, providing valuable insights for improving embankment stability analysis and facilitating the design of embankments.

A three-dimensional calculation model of a cylindrical lined tunnel and the surrounding unsaturated soil is established to analyze the response to internal explosion load by assuming that the transient load decays exponentially along the direction of the tunnel. The governing equations of lining structure and surrounding unsaturated soil under blasting load are derived based on the theory of porous media mixture and continuum mechanics. The analytical solutions of tunnel lining and surrounding unsaturated soil in frequency domain and wave domain are obtained by using Laplace and Fourier transform. The effect of saturation on the dynamic response of lining structure under the action of endogenous explosion is considered. The results indicate that the saturation has a substantial effect on the radial displacement of the inner surface of the lining. As saturation increases from 0.15 to 0.98, the radial displacement at the explosion source increases by about 28% in the axial direction. The variation of radial stress on the inner surface of lining with time is not significantly affected by saturation. The crest value of lining’s circumferential stress expands with increasing saturation and the time to achieve the apex is gradually postponed. In the axial direction, as the saturation increases from 0.15 to 0.98, the circumferential stress at the explosion source increases by about 29%.

This study investigates the influence of many factors, specifically the strength parameters of geotechnical materials, on the run-out distance of flow-like landslides. Due to the limitations of field tests and laboratory experiments, strength parameters of soils usually exhibit significant spatial variability with different scales of fluctuation (SOF) in different directions, which is the anisotropy of SOF. Aiming at the influence mechanism of anisotropic SOF of the cohesion random field on the run-out distance of flow-like landslides, this study introduced the mid-point method based on the Cholesky decomposition to generate the anisotropic random field. The smoothed particle hydrodynamics (SPH) analysis method, combined with the Mohr-Coulomb failure criterion and the non-Newtonian fluid model, was used to simulate the sliding process and run-out distance of landslides. A stochastic analysis method for the flow-like landslide motion process was established within Monte Carlo simulation framework. Then, by simulating the Yangbaodi landslide and the horizontal strata model, the applicability of the SPH method and the random field discretization method was validated. Finally, a conceptual landslide case was constructed based on the topographic data of the Wangjiayan landslide that was triggered by the Wenchuan earthquake. The study discussed the movement process under the anisotropic SOF in the random field of cohesion and analyzed the probability distribution characteristics of run-out distances. The results show that an increase in the vertical fluctuation range results in a wider range of variation in run-out distance, and the sliding distances exhibit a discrete nature; on the premise that the cohesion parameter conforms to the lognormal distribution, the distribution of the run-out distance also conforms to the same lognormal distribution, which proves that the run-out distance distribution of flow-like landslides is closely related to the distribution characteristics of inputted parameters.

Expanding the applicability of traditional limit equilibrium (LE) methods in slope stability analysis under complex conditions has been a research hotspot in geotechnical engineering field. It is recognized that the shear failure of geotechnical body of slope is typically governed by nonlinear strength criteria, while the traditional LE method is only applicable to the slope stability analysis under the linear strength criterion. Pre-stressed anchors, as an active protection measure, are widely used in the reinforcement of medium and large-scale slope projects because they can greatly and instantly improve the stability of slopes. However, the long-term stability characteristics of slope reinforced by the pre-stressed cables, including stress relaxation, creep, and the effects of corrosion, are often overlooked. To address these issues, an approach based on the Morgenstern-Price (M-P) has been developed. This method incorporates the nonlinear Mohr-Coulomb (M-C) criterion and integrates the pre-stress loss model of the cables under stress relaxation and creep effects, as well as the performance deterioration model of the cables under the influence of corrosion. In order to tackle the challenge of solving implicit nested formulas under the nonlinear strength criterion, the initial value of the inter-slice normal force is set to zero, and an iterative loop calculation strategy is applied. Subsequently, the approximation of the real theoretical results of slope stability can be realized by introducing the criterion of the allowable error of loop termination. Through comparison and analysis of various examples, the feasibility and rationality of this method have been verified. Furthermore, the variation patterns of long-term stability of slope reinforced by the pre-stressed cables under different pre-stressed loss rates and different corrosion environments are also studied.

In this study, a visual medium-scale direct shear test is carried out on the sliding zone soil with different coarse particle strengths. The spatial information of the shear band is obtained by placing a vertical aluminum wire to observe its deformation after shearing, and the spatial surface equation of the shear band is established. Particle image velocimetry (PIV) technology is used to extract and compare the 2D shear band information at the visible surface with the boundary extrapolation value of the space surface equation obtained from the test, demonstrating that the spatial surface equation and PIV technology can describe the characteristics of shear band. Then, PIV technology is used to analyze the evolution rule of shear band under different total and specific displacements. Finally, the influence of prefabricated damage and coarse particle strength on shear band characteristics was analyzed. Results show that the thickness of shear band presents a distribution pattern of narrow ends and wide middle, and its shape can be fitted by Gaussian surface equation. The shear band undergoes four stages during its development: compaction, free damage, damage development, and penetration. Damage causes early development of shear bands at various stages. Furthermore, coarse particle strength exerts a greater effect on the deformation of local shear bands and a smaller effect on the overall shear band. These findings hold significant implications for elucidating the formation and evolution of landslide shear bands and designing a rational slope control plan,

The existence of intercalation in sandy soil affect the pore pressure development in saturated sandy soil, thereby impacting the deformation of sandy soil layer. In order to study the pore pressure change during the liquefaction of sandy soil under different intercalation conditions such as location, thickness and type, a liquefaction test of laminated sand under impact load was conducted. This study involved establishing a theoretical model of saturated sandy soil with intercalations and comparing the test results with the theoretical analysis. The findings reveal that the development of pore pressure of saturated sandy soil containing intercalated layers exhibits three stages: rapid rise, rapid dissipation, and slow dissipation. In cases involving high-permeability intercalations, a higher location of the intercalation results in a shorter rapid dissipation time of pore pressure below it, leading to a faster convergence to a stable value. However, the total dissipation time shows no significant change. Conversely, for low-permeability intercalations, an increase in the height or thickness of the intercalation accelerates the rate of rapid dissipation phase of pore pressure above the intercalation, prolongs the stable phase of pore pressure dissipation, and linearly increases the total dissipation time of pore pressure. Additionally, a water film forms below the low-permeability intercalation, and increasing the intercalation height or thickness extends the duration of the water film, with the water film formation primarily affected by the intercalation thickness.. The test results are more consistent with the theoretical analysis, indicating the reliability of the test. The test results align more closely with the theoretical analysis, indicating the reliability of the test.

The study aimed to investigate the influence of dry-wet freeze-thaw cycles on the mechanical properties of undisturbed loess and evolution of microscopic damage. In order to analyse the stress-strain curves and chang law of strengch index and mesoscopic damage of pores from a macro and meso perspective, the research employed consolidation drainage triaxial shear tests (CD) and nuclear magnetic resonance tests under varying dry-wet freeze-thaw cycle durations. On this basis, the strength distribution of loess was assumed to follow a composite function, a statistical damage constitutive model of loess was established and its applicability was verified. The key findings and observations are summarized as follows. The stress-strain curve of the soil exhibited strain softening, with the degree of softening gradually decreasing with an increase in the number of cycles. The peak value of deviatoric stress decreased with the number of cycles and tended to be stable gradually, and the attenuation degree was most significant at the second cycle, decreasing by 17.6%, 23.2%, 24.5% and 18.1% respectively under different confining pressures. The circulation action led to damage to the cemented block in the soil, resulting in a gradual increase in internal pore area, primarily due to the transformation of small pores into large pores. With an increase in the number of cycles, the internal structure of the soil gradually became more stable.

The site fundamental period is a crucial variable for site effect models and serves as a significant index for seismic site classification. The existing methods for obtaining site fundamental period assume that the angle of incident seismic wave at the site base are vertical. These commonly used methods include simulation and empirical method based on the vertical SH wave propagation in seismic site. The empirical method of layer by layer single degree of freedom method is adopted in the Japanese seismic design code for its simple calculation and the results are equivalent to the simulation method. Nonetheless, the assumption of vertical incidence does not align with the actual incidence angle of ground motion at the site base. This paper addresses this discrepancy by focusing on establishing a method for the calculation of the basic period under obliquely incident seismic wave. First, the 2D SH wave propagation in seismic site under the action of oblique incidence wave is characterized as vertical 1D apparent propagation to establish the SH wave propagation model based on Snell law. Building upon this foundation, a wave propagation simulation model is applied to establish a numerical method and modified layer by layer single degree of freedom method for the calculation of the basic period and then applied to KiK-net stations. The findings indicate that the fundamental period decreases with an increasing incident angle. For the statistical average result of the base incident wave angle at 57°, the average deviation can be 11%. The modified method accurately considers the influence of the seismic wave incident angle, while maintaining calculation simplicity equivalent to the original method. Finally, the paper discusses the influence of selecting the bedrock surface burial depth on the calculated site fundamental period. The results demonstrate a high correlation between the basic period of the site and different depths if the top of the soil layer, with a shear wave velocity larger than 700 m/s, is defined as the bedrock surface.

Understanding the mechanical changes of marine soft soil under temperature is crucial for the construction and long-term operation of submarine pipelines. A series of basic physical and mechanical properties tests was carried out on the marine soft soil in Shanwei, Guangdong province. X-ray diffraction, X-ray fluorescence spectrometry, and scanning electron microscopy were employed to achieve the marine soft soil’s mineral composition, element composition and microstructure. The consolidated undrained laboratory tests under isotropic consolidation and biaxial consolidation conditions were carried out using a temperature-controlled triaxial apparatus. The test results revealed significant findings. Firstly, when the axial strain is small, the undrained shear characteristics of saturated marine soft soil are influenced by the ambient temperature and the consolidation stress ratio. Specifically, a higher ambient temperature or a smaller consolidation stress ratio results in a greater secant modulus. The secant modulus exhibits an inverse relationship with the consolidation stress ratio and demonstrates a power function relationship with the ambient temperature. As the axial strain increases, the peak strength of the soil is affected by both ambient temperature and consolidation stress ratio, while the peak pore pressure is less affected by ambient temperature. Furthermore, the initial dry density of the sample was found to impact the undrained shear characteristics of the isotropic consolidated soil (K_c=1.00). A greater initial dry density resulted in a smaller peak pore pressure, a greater peak strength, and a more significant decrease in peak strength with rising temperature. Additionally, the consolidation stress ratio was observed to affect the peak strength and effective stress path of saturated marine soft soil under different ambient temperatures. Specifically, when K_c=1.00 or 0.67, an increase in the ambient temperature softened the saturated marine soft soil; whereas when K_c=0.50 or 0.40, the rise in ambient temperature hardened the soil.

Dynamic compaction is one of the most convenient methods of ground improvement. It is crucial to reasonably analyze additional dynamic compressive stress on the compacted soil in practice. The typical mixed soil-rock fill in Chengdu plain is investigated in this study. The vertical dynamic stress at different depths in the soils subjected to dynamic compaction with an impact energy of 4 000 kN·m is tested in situ. Considering the difference between the observed results and those using the existing calculation methods, simplified and modified algorithms for the dynamic compressive stress are developed. On the one hand, parameter sensitivity analysis and linear regression analysis are conducted to simplify the existing complicated formula via eight parameters characterizing the surface impact stress including the mass of rammer, fall height, radius of the rammer, soil density, dynamic shear modulus, Poisson’s ratio, damping ratio, as well as impact velocity loss rate of the rammer. On the other hand, based on the pseudo-static method, a modified formula of the vertical dynamic stress at different depths of the soil is provided via introducing a transfer index into the elastic static stress dispersion equation, and the modified formula can be employed to analyze the effective impact depth. The example of the mixed soil-rock fill from the field test demonstrates a transfer index of 1.673 57 and an effective impact depth of approximately 8.0 m..

In order to determine the in situ stress state of the newly built hydropower station project in Jiacha county, and understand the activity of the eastern segment of the Yarlung Zangbo River fault zone, we obtained the in situ stress data in the engineering field by using the self-developed deep-hole stress measuring equipment based on the hydraulic fracturing method. We analyzed the fault activity by employing the Mohr-Coulomb failure criterion and the collected in situ stress data along the eastern segment of the Yarlung Zangbo River fault zone. The results showed that: (1) The magnitudes of the maximum horizontal stress SH ranged from 6.07 MPa to 37.62 MPa, the values of the minimum horizontal stress Sh were from 3.13 MPa to 20.33 MPa at the depth from 122.75 m to 418.75 m, and the dominant direction of the measured maximum horizontal principal stress was nearly NNE. (2) The stress regime was mainly characterized by S_H＞S_h＞S_v (S_v is the vertical principal stress), which was prone to reverse faulting. (3) Most of the measured and collected Mohr stress circles intersected the failure threshold line with friction coefficient equal to 0.6, which indicated that the eastern segment of the Yarlung Zangbo River fault zone was in a high level of fault slip instability. Furthermore, the fault slip risk of the west section from Gongga to Langxian was higher than that of the east section near Linzhi along the eastern segment of the Yarlung Zangbo River fault zone.

Image analysis of rock chips is an important approach for TBM intelligent tunneling, and it can be used for real-time evaluation of rock-breaking efficiency and optimization of tunneling parameters. In order to investigate the relationships between TBM tunneling parameters and rock chip characteristics, a multi-step field tunneling test was carried out in an intact granite formation at a TBM construction section of Qingdao Metro Line 6. A rock chip image acquisition system was installed on the TBM to real-time collect rock chip images. Then, the relationship between the tunneling parameters and the size and shape characteristics of rock chips obtained through image processing was analyzed. The results showed that the median particle size d50, maximum particle size dmax and roughness index CI all present a positive correlation with thrust, torque and penetration, while a good negative correlation with FPI and SE. When the thrust exceeds a critical value for rock-breaking, the increase in thrust will significantly increase d50 and CI, while dmax increases significantly only when the thrust exceeds a larger value. Besides, as the thrust increases, the shape of the large rock chips gradually becomes flattened and the aspect ratio increases. However, after the thrust reaches a certain level, the aspect ratio will remain stable. The results can provide a basis for real-time optimization of TBM tunneling parameters based on rock chip information.

In order to investigate the loading state of the combined structure of inner tension ring-segment-surrounding rock in tunnel boring machine (TBM) pressurized water conveyance tunnel, a three-dimensional refined finite element model of the composite structure comprising the inner tension ring-segment-surrounding rock in a TBM pressurized water conveyance tunnel has been established for the Class V TBM pressurized water conveyance tunnel of the Rongjiang-Guanbu water diversion project. The study has yielded important findings. The reinforcement of the tunnel structure with internal tensile steel ring can effectively control the deformation of the tunnel, reduce the tensile stress of the segment and the range of tension zone, and improve the bearing capacity of the composite structure. Under the action of internal water pressure, various parameters such as compression stress, vertical deformation, joint opening degree, stress of connecting bolts, stress of the inner tension ring, and stress of anchor rods all decrease compared to conditions without internal water pressure. However, the tensile stress of the segment and joint misalignment increase by 19.68% and 39.25%, respectively. The main reason is that the overall expansion of the tunnel structure is caused by internal water pressure. This underscores the need for strengthened safety monitoring during water filling operations. Under the combined action of external water and soil pressure and internal water pressure, the change of surrounding rock type lead to increased stress of connecting bolt, the misalignment of segment joints and the stress of anchor bolt by 37.11%, 15.29% and 14.75%, respectively. This highlights the importance of monitoring in the transition area of surrounding rock types where the load-bearing capacity is poorer. In addition, under the combined action of external water and soil pressure and internal water pressure, the load sharing rate of surrounding rock, segment, inner tension steel ring and anchor bolt is 21.38%, 43.08%, 24.01% and 11.53%, respectively. The load sharing rate of inner tension steel ring is 34.06% higher than that without internal water pressure. The effect of internal water pressure improves the load sharing effect of the inner tension steel ring. The load sharing ratio of surrounding rock in composite structure decreases with the increase of surrounding rock types (Class Ⅲ, Class Ⅳ, Class Ⅴ), and the load sharing ratio of class Ⅲ surrounding rock is 16.96% higher than that of Class Ⅴ under the same load. These research findings provide valuable theoretical reference for lining design and late reinforcement measures of similar tunnel projects.

Unlike conventional tunnel lining structures, the antecedence tunnel lining is subject to secondary disturbances from the later excavated tunnel excavation after the lining has been stabilized. The excavation impact of the later excavated tunnel on the surrounding rock pressure acting on the antecedence tunnel lining cannot be ignored. Relying on Yangjiazhai tunnel project, a calculation method for surrounding rock pressure that accounts for the influence of the second tunnel excavation has been developed. This method, in combination with on-site monitoring displacement data and utilizing the load-structure method for inverse analysis, proposes a means of determining the load acting on the antecedence tunnel lining. The field-measured values of the surrounding rock pressure behind the lining were used for comparison and verification. The study results have yielded important insights: 1) The impact of the second tunnel excavation on the first tunnel lining’s ability to withstand surrounding rock pressure is substantial, with the average increase in monitoring points reaching as high as 142%. 2) The pressure acting on the antecedence tunnel lining follows a distribution pattern of being lower at the waist of the arch and higher at the top and the shoulder, with the shoulder of the arch near the later excavated tunnel experiencing the greatest pressure. 3) The results of the surrounding rock loading obtained from the inverse analysis are more consistent with the field monitoring results, which argues for the soundness and practicality of the approach, and providing a reference basis for the structural design for the double-arch tunnel without middle drift.

With the increasing complexity of the three-dimensional cross-distribution system of pile foundations and tunnels in the urban underground space, the stability of the pile foundation caused by tunnel seepage erosion becomes more and more prominent. However, the current research mainly focuses on the mechanism of erosion induced by defective tunnels, and little on its interaction with the adjacent pile foundation. Thereby, based on the seepage erosion mechanism revealed by the physical model test, the erosion-induced stratum form is quantitatively characterized by establishing the critical fine particle content expression. Subsequently, a multi-zone eroded strata model is simulated by the random and quantitative removal of fine particles in the DEM domain, and then the erosion response characteristics of the foundation under different positions, loads, sinking methods and types are analyzed. The results show that the pile foundation has different degrees of subsidence under different erosion conditions, and tilts to the eroded area under the drive of unbalance force on its eroded position. After the erosion-induced reduction, the pile-tip resistance increases gradually with the subsidence, but the loss of lateral frictional resistance is basically unrecoverable. In addition, the changing mode of displacement and resistance of the pile is basically the same under different sinking methods and loads, only different in the changed amount. Compared with the single pile, pile group foundation has a better erosion resistance.

After the rapid disintegration of long run-out accumulation landslides, debris flows are often formed. They dynamically erode the underlying soft materials along their sliding paths and change the dynamic characteristics of landslide movement, which will lead to a significant increase in landslide volume. Long run-out accumulation landslides have strong disaster effects, which has become the focus of disaster prevention and mitigation research in recent years. To address the issue of quantitative prediction of dynamic erosion process for potential long run-out accumulation landslides, a continuum numerical model is constructed based on the depth-integrated hydrodynamic calculation theory and solid-liquid two-phase shear stress erosion model framework. The software program DisasterFlow V1.0 with second-order calculation accuracy is compiled for numerical realization. Through two classic case studies of dam-break flow, the results calculated by the developed model program are highly consistent with the actual situations. The developed numerical solution scheme is correct and has a good total variation diminishing (TVD) behavior. The prediction of dynamic erosion process for the long run-out accumulation landslide in Baiyanglin shows that the developed numerical model and the conventional sled model basically agree with the prediction results of the landslide sliding velocity. Compared with the conventional sled model, the developed numerical model has better adaptability to the terrain of the sliding path, resulting in less oscillation in the predicted values of the landslide sliding velocity. In addition, during the numerical prediction and analysis of the dynamic erosion process for the long run-out accumulation landslide in Baiyanglin, the developed numerical model can quantify the landslide dynamic erosion process in the time and space dimensions, such as quantifying the sliding depth, velocity and accumulation depth in each duration, which are not available in the conventional sled model. This paper provides a feasible quantitative prediction solution of the dynamic erosion process for long run-out accumulation landslides, which could enriches the quantitative prediction theory and technical system for long run-out landslides.

The coupling effect of layered soil characteristics and seismic action is rarely considered in the studies on the stability of shield tunnel excavation face. In this study, a three-dimensional logarithmic spiral failure model of shield tunnel excavation face considering seismic action in layered soil is constructed for study. Firstly, the dynamic response caused by earthquake is reduced to the inertia force in horizontal and vertical directions using pseudo-static method. Secondly, the three-dimensional logarithmic spiral failure mechanism, initially designed for homogeneous soil, is improved to be suitable for layered soil. Then, according to the upper bound theorem, the power of seismic inertia force is introduced into the virtual power equation to derive the upper bound solution of the support force of shield tunnel excavation surface considering the soil stratification characteristics and seismic action conditions. Finally, the theoretical upper bound solution is compared with the 3D numerical simulation results, engineering measured results and existing experimental results, showing good agreement. Furthermore, the key physical characteristics are analyzed according to the horizontal seismic acceleration coefficient and formation thickness. The results show that when the proportional coefficient ζ > 0, the ultimate supporting force increases significantly with the increase of horizontal earthquake acceleration coefficient. Conversely, when ζ < 0, the increasing trend of ultimate supporting force decreases with the increase of horizontal earthquake acceleration coefficient. Additionally, when horizontal earthquake acceleration coefficient kh=0, that is, in the absence of earthquake action, the normalized ultimate supporting force does not change with the change of proportion coefficient ζ. Moreover, in the hard above and soft below layered soil, an increase in the thickness ratio of the lower soil layer leads to an increase of the ultimate supporting force. In contrast, in the soft above and hard below layered soil, an increase of the thickness ratio of the lower soil layer results in a decrease of the ultimate supporting force.

The study focuses on investigating the influence of initial pores on the mechanical behavior of vesicular amygdaloidal basalt using a stochastic three-dimensional modeling method. The proposed modeling method considers calculated porosity, volume parameters, shape parameters, angle parameters, and structural parameters. Subsequently, five-factor and five-level orthogonal numerical simulations under uniaxial compression are conducted to analyze stress‒strain curves, damage modes, and failure characteristics. The calculated porosity, angle parameters, and structural parameters are found to strongly influence the uniaxial compressive strength (UCS) and elastic modulus of the rock. Specifically, the UCS and elastic modulus exhibit negative correlations with calculated porosity and angular parameters, while showing positive correlations with structural parameters. Weak correlations are observed with the remaining factors. The percentage of plastic strain in the stress‒strain curve of vesicular amygdaloidal basalt is noted to increase with increasing model porosity. The damage mode shifts from a single-shear surface, multiple-shear surface to local crush damage. Additionally, the rock transitioned from brittle to ductile failure. It is identified that a porosity of 5% and 12.5% can be approximated as critical values for the strong brittle‒brittle‒ductile transition. The established damage statistical constitutive equation is found to better predict the mechanical behavior of vesicular amygdaloidal basalt based on the initial pore. This suggests the potential importance of determining the mechanical properties of porous rocks in basaltic formations.

Under the combined effect of rainfall and water level fluctuation, the slope of the reservoir bank is prone to collapse. Ideal elastic-plastic Mohr-Coulomb criterion is used to analyze the stability of reservoir slope, which is difficult to characterize the complex mechanical characteristics of slope soils, such as over consolidation dissipation under wet-dry cycles. It is difficult to analyze the stability of bank slopes under the action of dry and wet cycles to reflect the complex mechanical properties such as overconsolidation and dissipation of slope soils. In this study, focusing on weakly overconsolidated unsaturated red clay at the reservoir bank slope of the Xingan shipping-hydropower junction project in Jiangxi Province, unsaturated direct shear tests were conducted and an overconsolidated unified hardening (UH) model for red clay was constructed. The UH model incorporates the mathematical-physical relationship between suction stress and matric suction using the arctangent function. Subsequently, based on the UH model, an application program of FLAC3D was developed in C++. The SEEP/W module of GeoStudio software was employed to compute the unsaturated seepage field during the rainfall infiltration, and an interface program was created to import FLAC3D data for stability calculations of the reservoir slope. Comparisons between the horizontal displacements obtained from the improved UH model and the classical unsaturated elastic-plastic model revealed significantly larger displacements in the former, suggesting that the improved UH model can provide reasonable predictions of the overconsolidated unsaturated red clay for reservoir slope stability. This research offers valuable insights for similar projects involving analyses of reservoir bank slope.

The particle impact-assisted rock-breaking technology offers the advantages of high speed and efficiency, demonstrating effective rock-breaking capabilities on hard rock. In a recent study, the author investigated the influence of impact speed of single and double particles, the distance between double particles, and other factors on the surface, three-dimensional and sectional morphology characteristics of high-strength granite. This investigation involved a combination of particle impact testing and discrete element simulation. The study aimed to elucidate the impact parameters’ influence on the changes in impact crater depth, volume, and surface area. Additionally, it examined the distribution of rock-breaking cracks caused by particle impact and evaluated the effectiveness of hysterisis double-particle impact rock-breaking from the perspective of energy absorption rate. The results revealed a positive correlation between impact crater depth and impact velocity. Moreover, as the distance between particles increased, the impact crater underwent morphological changes, becoming separated, with a decrease in volume and an increase in surface area. The simulations indicated that the cracks primarily distributed at the grain boundaries of plagioclase and orthoclase feldspar, with the dominant failure mode being tensile failure. Furthermore, when employing a 5 mm-diameter steel particle on 200 MPa extremely hard granite, the energy absorption curve of hysterisis double-particle impact rock-breaking tended to flatten with increasing impact velocity. Notably, at a particle distance of 8–10 mm and an impact velocity of around 400 m/s, the optimal impact-assisted rock-breaking effect was achieved.

The distribution of the mesh significantly impacts the accuracy of calculation in the three-dimensional lower bound finite element limit analysis method (3D LB-FELA). Achieving precise lower bound solutions requires a dense mesh to be pre-divided in the failure area, which can easily lead to excessive calculation scale and reduce solving efficiency. To address these challenges, this paper proposes a "posterior" adaptive mesh refinement strategy. Firstly, the paper proposes a 3D LB-FELA based on M-C criterion and semi-definite programming technique, which eliminates the need for approximating the yield criterion. Subsequently, it introduces an adaptive mesh refinement strategy based on the M-C criterion, determining the coordinates of the refinement points by evaluating the degree to which each element's stress approaches yield. This approach involves combining the refinement points with the original nodes to form a new point set, followed by re-meshing the mesh. Finally, the proposed method is used to study the tunnel stability, and the research results demonstrate that the proposed mesh adaptive refinement strategy can accurately simulate the stress distribution in the failure area with smaller scale elements, thereby obtaining high-precision lower bound solutions.