Fissured loess slopes along the railway in the Loess Plateau frequently suffer from disintegration disasters under the coupled effects of rainfall and train vibrations, causing soil collapse that covers tracks and severely threatens railway safety. To reveal the disaster mechanisms, this study conducted water-vibration coupled disintegration tests on fissured loess using the self-developed EDS-600 vibration disintegration apparatus, based on the measured dominant vibration frequencies (12-46 Hz) of the Lanzhou-Qinghai Railway. The influence patterns of vibration frequency (f) and fissure type (t) on disintegration rate (S), disintegration velocity (V), and disintegration velocity growth rate (\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\alpha_{f - t}$$\end{document}) were systematically investigated, with scanning electron microscopy (SEM) employed to uncover microstructural evolution mechanisms. Results indicate that vibration frequency and fissure type significantly accelerate disintegration: V reaches its maximum at f = 20 Hz, and under the same frequency, V increases with the growth of fissure-water contact area. Under two fissures and f = 20 Hz, V increases by 225% compared to the without vibration and fissures scenario, with the \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\alpha_{f - t}$$\end{document} value peaking at 137.23% and the synergistic effect index exceeding the single-factor superposition value by 45.99%. Microscopically, water-vibration coupling disrupts clay mineral cementation, reconstructs pore networks, and forms dominant seepage channels, leading to reduced interparticle bonding strength, heterogeneous water film distribution, and stress concentration, thereby inducing fractal propagation of secondary fissures and shortening moisture absorption and softening stages. Combined with unsaturated soil mechanics theory, the study reveals a cross-scale progressive failure mechanism involving simultaneous degradation of matric suction, cementation force, and macroscopic strength. A theoretical framework integrating vibration energy transfer, seepage migration, and structural damage is established, along with a quantitative relation linking vibration frequency, fissure parameters, and disintegration velocity. This provides multi-scale theoretical support for disaster prevention and control of railway slopes and foundations in loess regions.

Granite saprolite (GS) slope failure is a common yet catastrophic phenomenon in South China. Although the impact of subtropical climate, characterized by high temperatures and heavy rainfall, is widely recognized, the effect of the capillary imbibition and drying (CID) process, which frequently occurs during the dry season, on the hydro-mechanical properties of GS and slope stability is largely overlooked. This research examines natural GS specimens with various degrees of weathering subjected to CID cycles. The study investigates the capillary imbibition (CI) process and the evolution of the soil's hydromechanical properties across CID cycles. The results indicate that the CI process in GS is fundamentally different from that in clays and sands. The aggregated structure of GS comprising numerous fissures and large pores plays a critical role. In addition, the CID cycles cause the hydro-mechanical degradation of GS, including a finer particle composition, decreased shear strength, and increased permeability and disintegration potential, where damage to soil cementation and fissure development are identified as critical factors. This investigation reveals new insights into the mechanical properties of GS that are essential for the development of effective landslide management strategies in South China. (c) 2025 Institute of Rock and Soil Mechanics, Chinese Academy of Sciences. Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/ 4.0/).

Earth fissures pose a significant risk to the seismic safety of underground structures at earth fissure sites (USEFs), particularly for large-scale underground frame structures such as subway stations. To date, the failure mechanism of USEFs has only been analyzed qualitatively and requires further comprehensive investigation. Moreover, the existing failure prediction methods for USEFs are complicated, challenging to execute, time-consuming, and incur significant financial costs, necessitating the establishment of a simple and efficient failure prediction method. This study conducted a shaking table test on a USEF to investigate the dynamic response of earth fissure sites and the seismic damage characteristics of a USEF. Based on the experimental results, a tailored pushover analysis method was developed to predict the seismic failure of the USEF and was applied to reveal its underlying seismic failure mechanisms. It was found that low-frequency ground motions are significantly amplified at the earth fissure site and that the acceleration amplitudes at the hanging wall and footwall are nonuniform. This nonuniform acceleration leads to significant extrusion and separation between the hanging wall and footwall. The extrusion causes the soil to rise, exerting additional axial pressure and bending moments on the lateral resistance members. These additional forces lead to uneven internal force distributions within the USEF, highlighting that structurally weak members are prone to failure and accelerating structural damage. The bottom column at the hanging wall is the critical seismic member of the USEF, which requires focused reinforcement and monitoring to increase resilience. The tailored pushover analysis method accurately represents the deformation characteristics at earth fissure sites. The method captures distinct structural destruction patterns, enhancing its utility in seismic failure prediction for USEFs.

The stability of loess high-fill slopes is a crucial issue in engineering, where the presence of fissures significantly impacts slope stability. This study investigates the seepage-mechanical response and fissure evolution characteristics of loess high-fill slopes under the coupled effects of consolidation, rainfall, and evaporation through model testing. The disaster chain evolution process of the slope under these coupled effects is revealed. The results show that the development of fissures in loess high-fill slopes does not follow a directional pattern and has a uniform influence on soil properties. Under rainfall, the slope exhibits preferential flow paths, which guide the deformation and failure modes. With the development of fissures, the fill material shows a cumulative damage effect, leading to progressive performance degradation and continuous decline in slope stability. This study enriches the theoretical framework for stability analysis of high-fill fissured slopes and provides guidance for disaster prevention and mitigation in loess regions.

The large number of fissures developed in loess affect the creep mechanical properties of the soil body, easily triggering geologic disasters such as loess landslides. To gain a comprehensive understanding of the creep characteristics of fissured loess, we used the undisturbed loess from the landslide group in the Heifangtai area of Gansu Province, China, to conduct triaxial creep tests under various prefabricated fissure angles (without fissure, 30 degrees, 45 degrees, 60 degrees, and 90 degrees) and different matric suction conditions. The stress-strain-time characteristics of fissured loess are analyzed, and the long-term strength variation law of fissured loess is determined. The deterioration effect of loess fissures is revealed, and the creep deformation characteristics of fissured loess samples (FLS) are explored. The results show that: (1) The deviatoric stress, confining pressure, and matric suction significantly affect the creep deformation of fissured loess and the duration for the sample to attain steady-state creep. (2) The fissures have a pronounced deteriorating effect on the long-term strength of loess. As the fissure angle increases, the long-term strength of the loess sample initially decreases and subsequently increases, exhibiting a V shaped variation, while the cohesion demonstrates a comparable V shaped variation. (3) The deterioration coefficient of the fissure initially rises and subsequently declines with increasing confining pressure. (4) The creep deformation characteristics of FLS are categorized into axial deformation, bending deformation, and torsional deformation. Generally, the fissure angle affects the axial strain of the sample; however, an increase in confining pressure weakens the influence degree of the fissure on the deformation. The findings provide new insights into theoretical support for the study of loess mechanics and deformation characteristics in the Loess Plateau region of China. This is significant in elucidating the effect of fissures on the occurrence and development of loess landslide disasters.

The recent upsurge in metro construction emphasizes the necessity of understanding the mechanical performance of metro shield tunnel subjected to the influence of ground fissures. In this study, a largescale experiment, in combination with numerical simulation, was conducted to investigate the influence of ground fissures on a metro shield tunnel. The results indicate that the lining contact pressure at the vault increases in the hanging wall while decreases in the footwall, resulting in a two-dimensional stress state of vertical shear and axial tension-compression, and simultaneous vertical dislocation and axial tilt for the segments around the ground fissure. In addition, the damage to curved bolts includes tensile yield, flexural yield, and shear twist, leading to obvious concrete lining damage, particularly at the vault, arch bottom, and hance, indicating that the joints in these positions are weak areas. The shield tunnel orthogonal to the ground fissure ultimately experiences shear failure, suggesting that the maximum actual dislocation of ground fissure that the structure can withstand is approximately 20 cm, and five segment rings in the hanging wall and six segment rings in the footwall also need to be reinforced. This study could provide a reference for metro design in ground fissure sites. (c) 2025 Institute of Rock and Soil Mechanics, Chinese Academy of Sciences. Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/ 4.0/).

With the advancement of ecological and environmental protection construction, the research on the modification of expansive soil using environmentally friendly polymers can make up for the harm to the ecological environment caused by traditional modification. Mechanical and microscopic properties of modified expansive soils were analyzed through indoor tests. The results showed that the liquid limit and plasticity index decreased by 52.14% and 77.36%, respectively, and the plastic limit increased by 20.83%. Maximum dry density decreased by 5.11% and optimum moisture content increased by 28.47%. The compressive and shear strength increases and then decreases with the increase of dosage, and the strength reaches the maximum when the dosage is 4%, and the vertical and lateral deformation of the specimen is the smallest. Modified soil swelling was reduced by 54.57% and swelling forces were reduced by 15-57%. The modified soil cracks developed slowly and the width of the cracks was reduced by 61.68% after the modification. Microscopy showed that no new minerals were generated after doping modifier, while hydrophilic minerals were reduced by 43.14%, and the gel film formed by hydration made the pores smaller and the structure tighter by filling and wrapping on the surface of the particles.

Variations in excavation construction periods for fissured soil transportation engineering lead to differing unloading rates, which affect the soil's mechanical properties. This study utilizes a triaxial testing system to conduct monotonic and cyclic loading undrained shear tests on undisturbed fissured samples as well as remolded samples subjected to three distinct unloading rates. The K0 consolidated samples are regarded as soil mass that undergoes no unloading during testing. The findings indicated that the initial unloading rate influences the reloading shear mechanical properties of undisturbed and remolded specimens. The effects of unloading rates differ between undisturbed and remolded soil, a discrepancy attributed to inherent fissures. Specifically, undisturbed soil exhibits significant damage at low unloading rates due to fissures, while remolded soil experiences strength augmentation due to compaction with decreased unloading rates. Similarly, unloading will cause a loss of strength. Structural disparities result in the monotonic loading strength of undisturbed specimens being higher than that of remolded ones. In contrast, remolded specimens demonstrate greater dynamic strength under cyclic loading, likely because fissures deform, diminishing overall dynamic strength. Subsequent microscopic analysis, utilizing SEM images, along with a discussion of macroscopic inherent fissures, elucidated the impact of unloading rate on soil damage mechanisms, advancing the understanding of fissured soil behavior post- unloading. The study of mechanical properties of fissured soil following varying unloading rates is crucial for comprehending its damage mechanism and determining post-unloading soil strength parameters, providing valuable insights for practical applications in soil engineering.

In order to study the deformation law and failure characteristics of shield tunnel obliquely crossing ground fissure under earthquake action, taking the shield tunnel of Xi 'an Metro Line 8 crossing f3 ground fissure as the engineering background, the 1: 20 shaking table model test method was used to analyze the strain of shield tunnel, the contact pressure with surrounding rock soil, the dislocation of segment and the axial force of bolt in detail, and the seismic damage mechanism and failure characteristics of shield tunnel obliquely crossing ground fissure were obtained. The test results show that under the action of earthquake, the shield tunnel has complex three-dimensional deformation characteristics, among which the vertical deformation is the most obvious. The deformation is mainly concentrated in the location of the ground fissure. The tensile strain and contact pressure of the hanging wall of the tunnel segment are greater than the strain value and contact pressure of the footwall. Because the vertical deformation of the tunnel is the largest, the bolts at the vault and the arch bottom are most obviously pulled. Excavation after the test, it can be seen that the tunnel appeared the phenomenon of ring joint opening, lining cracking and other damage. Under the action of the earthquake, the shield tunnel across the ground fissure is mainly subjected to tensile failure. The failure area is within 10 m from the ground fissure in the hanging wall and footwall, and the total length is 20 m. The closer to the ground fissure, the more serious the damage. The research results provide a scientific and reasonable reference for the subsequent construction and disaster prevention and mitigation design of Xi 'an Metro.

The Qinghai-Tibet Plateau (QTP) has an extensive frozen soil distribution and intense geological tectonic activity. Our surveys reveal that Qinghai-Tibet Plateau earthquakes can not only damage infrastructure but also significantly impact carbon dioxide emissions. Fissures created by earthquakes expose deep, frozen soils to the air and, in turn, accelerate soil carbon emissions. We measured average soil carbon emission rates of 968.53 g CO2 m(-2).a(-1) on the fissure sidewall and 514.79 g CO2 m(-2).a(-1) at the fissure bottom. We estimated that the total soil carbon emission flux from fissures caused by M >= 6.9 earthquakes on the Qinghai-Tibet Plateau from 326 B.C. to 2022 is 1.83 x 10(12) g CO2 a(-1); this value is equivalent to 0.51% similar to 1.48% and 2.34% similar to 5.14% of the increased annual average carbon sink resulting from the national ecological restoration projects targeting forest protection and grassland conservation in China, respectively. These earthquake fissures thus increased the soil carbon emission rate by 0.71 g CO2 m(-2).a(-1) and significantly increased the total carbon emissions. This finding shows that repairing earthquake fissures could play a very important role in coping with global climate change.