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/).

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.

Loess has unique physical, hydrodynamic and mechanical properties, which are influenced by both internal and external geological processes, as well as human engineering activities. Consequently, surface disasters are especially prevalent in the Loess region of China. The study area is situated in the middle part of L & uuml;liang Mountain in the middle part of the Loess Plateau, which is characterised by a typical loess landform with a complex system of gullies and hill ridges. According to current theory, the cracking boundary of the goaf profile is a straight line. However, these surface disasters are actually caused by the shear action of the deep rock layer and the original vertical joint structure of the loess. By analysing the cracking process of the 'Goaf-Overburden-Loess' in the study area, it can be found that the boundary of the movement basin presents a broken line shape, which has important implications for the accurate estimation of the area affected by loess-type surface subsidence.

Nearly 1 100 fissures have formed on the Hebei Plain in China. Within the Yellow River-Qinghe River-Zhanghe River shallow buried paleochannel band on the plain, 93 ground fissures controlled by paleochannels have developed, of which the Wuyi-Fuping ground fissure is a typical paleochannel-controlled fissure located in Hengshui, Hebei Province, with a total length of 3 km, a dominant strike of NE78 degrees, and nearly upright in the shallow layer. The surface damage observed in this fissure primarily manifests as beaded pits, and its activity shows distinct segmentation characteristics. On the trench profiles, the offset distance of shallow layers remains consistently around 20 cm within the depth range of 0 to -3 m. An evident flexure is observed in the strata at depths ranging from -4.5 to -7 m. The drilling profile reveals that there is an absence of dislocations in the deeper strata. Nonetheless, the shallow seismic physical profiles unveil the presence of underlying faults beneath the study area, underscoring the intricate formation process and genesis mechanism of the Wuyi-Fuping ground fissure. Firstly, the formation and evolution of the Qingling River's paleochannel were shaped by the actions of fault blocks and underlying faults. The interplay of the regional stress field, fault block movement, and fault activity played pivotal roles in driving the development of this paleochannel. Secondly, the paleochannel exerts a controlling influence on the development location and severity of the fissure. During pumping, the confined aquifer within the paleochannel undergoes water loss and compression, resulting in the formation of a surface subsidence funnel. When the tensile stress surpasses the soil's tensile strength at the funnel's edge, the soil fractures give rise to a ground fissure. Finally, large amounts of surface water generated by heavy rainfall and irrigation can cause existing hidden ground fissures to rupture, emerge, and expand. This paper provides a heretofore generally unknown example, promotes research on the mechanisms of paleochannel-controlled fissures, and has guiding significance for disaster prevention and reduction in this area.

The causes of ground fissure formation are closely related to the change in the stress state in a loose layer, but many researchers often ignore the dynamic processes of mining when studying mining-induced damage mechanisms. The study of stress evolution in a loose layer during mining can help to reveal the causes of surface damage and its self-healing mechanism. This paper establishes a numerical model to study a loose layer's stress evolution and its causes during mining. The discriminative conditions of the potential dynamic fissure formation cycles and self-healing are given. The vertical and horizontal stresses in the loose layer at the mining boundary increase and then decrease under the mining disturbance, and the vertical stresses in the loose layer above the comprehensive mining surface undergo two increasing and decreasing stages, while the horizontal stresses increase and decrease and then increase again. The permanent fissures at the mining boundary form because of the decompression- and compression-related damage caused by horizontal unloading, while the dynamic fissures in the loose layer at the mining surface form due to the first horizontal unloading effect; the shear damage is caused by the second increase in vertical stress. Additionally, the soil Mohr-Coulomb strength criterion and the linear elastic stress-strain relationship are used to discriminate the single- and double-cycle development patterns of the dynamic fissures on the ground surface.

The Yuncheng Basin is part of the Fenwei Graben System, which has developed ground fissure hazards that have caused serious damage to farmland, houses, and roads and have brought about huge economic losses. Located in Wanrong County on the Emei Plateau in the northwestern part of the Yuncheng Basin in China, the Wangjiacun ground fissure is a typical and special ground fissure developed in loess areas, and its formation is closely related to tectonic joints and the collapsibility of loess. In order to reveal the formation and genesis of the Wangjiacun ground fissure, the geological background, developmental characteristics, and genesis pattern of the Wangjiacun ground fissures were studied in detail. A total of three ground fissures have developed in this area: a linear fissure (f1) is distributed in an NNE-SSW direction, with a total length of 334 m; a circular fissure (f2) is located near the pool, with a total length of 720 m; f2-1, a linear fissure near f2, has a fissure length of 110 m and an NE orientation. This study shows that tectonic joints in loess areas are the main controlling factors of the linear fissure (f1); differential subsidence in the pool caused by collapsible loess is the main source of motivation for the formation of the circular fissures (f2, f2-1), and tensile stresses produced by the edges of subsidence funnels lead to the cracking of shallow rock and soil bodies to form ground fissures (f2, f2-1). This study enriches the theory of ground fissure genesis and is of great significance for disaster prevention and the mitigation of ground fissures in loess areas.