The ground penetrating shield tunnel (GPST) method offers a streamlined approach to tunnel construction in soft ground with limited open-cut excavation. To explore the seismic response of GPST linings, a series of large-scale shaking table tests have been conducted, including a variety of seismic excitations. This paper focuses on lateral harmonic excitation. The model tunnel spans a total length of 7.7 m, with the embedment depth ranging from -0.5 to 0.5 times its diameter. The design and fabrication of the model tunnel are presented, including the segmental lining, along with circumferential and longitudinal joints. The soil was modeled with artificial synthetic soil, aiming to simulate the static and dynamic characteristics of the prototype soil. Its composition was adjusted and verified through element tests. The experimental results provide insights into the seismic response of the soil-tunnel system, the ovaling deformation of the segmental lining, as well as the response of the joints between lining segments. The results reveal a strong influence of embedment on tunnel seismic response. The reduction of tunnel embedment leads to a significant increase in lining accelerations and a phase difference, resulting in a whiplash effect. In contrast, the ovaling deformation of the lining and the joint apertures decrease with the reduction of embedment. In the sections of the tunnel that are fully embedded, both the acceleration and deformation response of the lining are governed by soil-structure interaction (SSI). A pronounced whiplash effect is observed in the sections of the tunnel that are not fully embedded, due to the absence of soil confinement. The presented experimental results offer valuable insights into the seismic response of GPSTs, which can be of crucial importance for their seismic design.

With the rapid advancement of rail transit, shield tunnels have been extensively constructed worldwide. However, leakage at the shield tail can lead to severe consequences, including shield machine subsidence, structural damage to the tunnel, or even catastrophic tunnel collapse. Research on tunnel collapse induced by shield tail leakage remains in its infancy. The mechanisms underlying such accidents are not yet fully understood by researchers and engineers, and effective preventive measures have yet to be developed. In this study, a reducedscale model test was conducted to investigate the processes and mechanisms of tunnel collapse induced by shield tail leakage. The findings reveal that tunnel collapse is primarily triggered by the impact loads generated from the destabilized soil cave. The soil cave, formed due to erosion caused by leakage, propagates upward in a cycle of destabilization and regeneration until the ground surface collapses, resulting in load redistribution around the tunnel. Additionally, the study compares tunnel collapses induced by shield tail leakage and connecting passage leakage, highlighting that while both share similar collapse mechanisms, their boundary conditions differ. The coupling effect between the tunnel structure and surrounding soil is more pronounced in shield tail leakage, leading to more intense load fluctuations and greater structural damage to the tunnel.

When subjected to external loads from the ground and nearby construction, tunnel segmental lining joints are prone to damaging deformation. This can result in water leakage into tunnels, posing great safety risks. With this issue in mind, we conducted a series of full-scale tests to study the effects of external loads on the waterproofing performance of longitudinal joints. A customized rig for testing segmental joints was developed to assess the effect of loading magnitude, eccentricity, and loading-unloading-reloading cycles on waterproofing performance. Additionally, the relationship between joint force, sealing gasket deformation, and waterproofing pressure was investigated. The results indicate that: (1) the sealing gasket's compression rapidly decreases as external loads increase, which weakens the waterproofing capacity of the joint; (2) the watertightness limit dramatically decreases as the bending moment increases; (3) a loading-unloading-reloading cycle leads to degradation of the joint' s waterproofing performance. The findings of this study provide a reference for subsequent waterproofing design of segmental tunnel joints, helping ensure the safety of tunnels throughout their operational lifespans.

The position of seal roof block may greatly affect the overall performance of the segmental tunnel. However, a few investigations have been dedicated to evaluating this effect. In the present study, finite element models are established to simulate the ring structure-soil model in order to evaluate the capacity curve of the universal ring structure during progressive failure. Nineteen universal ring structures configurations were analyzed considering different locations of the adjacent seal roof blocks. The models accurately simulated the structural details of the typical handhole for curved bolt in the circumferential and longitudinal joints. The seismic performance of the universal ring structure with different configurations is evaluated and discussed in terms of the moment curve, plastic zone distribution, joint opening angle curve and capacity curve of the universal ring. The results indicate that there are significant differences in the maximum positive and negative moment, plastic zone, and tensile angle of the universal ring structure when the seal roof block is in different positions. At the same time, the development of the performance curve of the ring will also show significant differences, especially in the elastic stage. The structure exhibits best seismic performance when the seal roof block is located at arch shoulder and waist (- 67.5 degrees +/- 22.5 degrees) because it is less likely to reach the normal function, immediate operational, rectifiable or irreparable damage stages compared to other configurations.

The fault dislocation produces severe additional deformation on cross-fault tunnels along the axial direction, seriously threatens tunnel safety. To this end, a simplified analytical model for evaluating the mechanical behavior of segmental tunnels subjected to buried fault dislocation was established. The segmental tunnel is treated as a Timoshenko beam acting on the Vlasov elastic foundation. The plastic yield of circumferential joints, the effect of frictional resistance along the axial direction, and the deformation characteristics of overburden soil after faulting were considered. Then, the reasonability of the analytical solution is proved by 3D numerical simulation. The tunnel safety state was evaluated based on the joint deformation of the segmental tunnel. Subsequently, the effects of plastic yield behavior between segmental rings, plastic equivalent bending stiffness ratio, segment dimensions, and longitudinal bolt on the longitudinal response of the segmental tunnel linings were investigated. The results show that the simplified analytical solution proposed is reasonable in predicting the joint deformation between segmental rings when the segmental tunnel is subjected to buried fault dislocation. When the normal faulting is imposed, the segmental tunnel is dominated by tensile deformation along the tunnel axial. Under 20 cm of normal faulting, the joint opening between segmental rings is close to the deformation control value of joint waterproofing. However, the shear deformation has been significantly weakened due to the effect of faulting in the propagation process to the surface. The calculation result is too small when the plastic deformation behavior is ignored. The plastic equivalent bending stiffness ratio eta 2 inversely correlated with the maximum joint opening. Increasing the strength grade or the number of longitudinal bolts has a relatively limited effect on reducing the opening between segment rings, where the joint still has a greater risk of water leakage.