Dynamic response of deep buried tunnel structure crossing fault under the action of seismic waves was numerically analyzed based on the discrete element theory to explore the fundamental deformation and failure characteristic of tunnels. The simulation tests took fault location, normal distance between fault and tunnel center, fault dip angle and surrounding rock grade as design factors. All the lining structures showed deformation characteristics from elliptic mode to twisted mode under seismic waves with regardless of the spatial relation of the tunnel and fault. The surrounding rock mainly failed in shear and the plastic zone of the rock mass near the fault extended to the fault. When the fault passing through the center of the tunnel, the lining deformed in shear due to the seismic induced activation of the fault, and the plastic zone of surrounding rock extended along the fault plane. With the constant fault dip angle and surrounding rock grade, the greater the normal distance between the fault and tunnel was, the safer the tunnel was. With the constant normal distance and surrounding rock grade, the plastic zone area of surrounding rock decreased first and then increased with the increase of fault dip angle, vice versus for the maximum residual displacement of lining. When the surrounding rock grade was Ⅲ, the lining showed roughly circular deformation characteristic instead of obvious elliptic deformation and the plastic zone area of the surrounding rock was significantly reduced comparing to that of grade Ⅳ surrounding rock. When the surrounding rock grade was Ⅴ, the fault influence on the tunnel deformation was not obvious, and the lining finally showed convergent deformation characteristic.

This paper studied the seismic response law of ground motion influenced by built road tunnel at specific site conditions in soft soil. The acceleration response of ground at surface from tunnel axis horizontally was investigated when buried depth of a round tunnel and input motion of base excitation vary, in the given site, by means of numerical method. Regularized amplitude and its Fourier spectrum of acceleration response were established as a scale of the influence index. The results showed that the regularized Fourier spectrum amplitude of acceleration varies periodically with input frequency and buried depth if uniform site were supposed. Whereas at practical layered site, the regularized acceleration Fourier spectrum amplitude gradually approached constant 1.0 if the distance between the observation point and the tunnel axis increased and either if buried depth increased. Especially, when the distance between the surface and the tunnel axis exceeded 2.5D or the buried depth exceeded 2.5D, the maximum amplification of Fourier spectrum amplitude of acceleration was less than 20%.

A prediction method of seismic response of circular tunnel based on artificial neural network was proposed. Taking the peak value of bedrock ground motion, the buried depth of tunnel, the relative stiffness ratio of stratum to structure and the contact condition between tunnel and stratum as the basic input parameters, the key response indexes of lining stress and deformation including bending moment, axial force, shear force and diameter change rate of circular tunnel under different ground motions were predicted. Through the response acceleration method, 320 sets of numerical calculation models for seismic response of tunnel structures composed of different input parameter values were established. The results were extracted to obtain the data set of this research and used for the establishment and test of the prediction model. The results showed that the mean square error and correlation coefficient of the response prediction value and the reference value of each group of models performed well, which verified the feasibility of the analysis model. Based on the prediction model after data training, the seismic response of tunnel structure under arbitrary ground motion input could be obtained, and then the prediction formula of seismic response of circular tunnel could be fitted. The validity of the method was verified by comparing with the classical analytical solution of seismic response of deep buried circular tunnel under degraded conditions. This method could also conveniently and quickly analyze the sensitivity influence ranking and effect of basic input parameters, which provided a new analysis method for seismic design and analysis of underground structures.

Previous seismic damage of the underground shafts have shown that the structural safety of shaft are facing seriously threat under strong earthquakes and damage occurs near the rock soil interface. In actual engineering, the shaft inevitably crossed the geotechnical interface, and the seismic damage failure mechanism of the shaft structure at the site of the geotechnical interface had not yet been clarified. This research mainly studied the influence of the shaft lining strength and thickness parameters on the damage of the shaft under the horizontal earthquake motion. Based on the finite element software ABAQUS, a three-dimensional soil structure interaction model of shaft was established. The internal force distribution, diameter deformation rate, damage state and strain distribution of the shaft under the action of horizontal earthquake motion were studied by three-dimensional dynamic time history analysis method. The results showed that the axial force, shear force and bending moment of the shaft at the geotechnical interface were mutated, the axial thrust force was the tensile force at the geotechnical interface, while the hoop force was the pressure force. The damage position of the shaft was concentrated at the intersection of rock and soil and was manifested as tensile damage; The axial thrust force is the damage control force, and the axial tensile damage was aggravated as the strength and thickness of the shaft lining increased; The peak axial strain of the shaft was concentrated at the geotechnical interface; The axial strain of the shaft lining with a wall thickness of 0.6 m under C35 concrete strength was 1.3 times that under a wall thickness of 0.5 m.

In order to study the influence of changes of stress states and mechanical properties of soils around the tunnel caused by shield tunnel construction on the seismic response of tunnel, the effects of stress release and soil disturbance induced by shield tunnel construction on the deformation of surrounding soil, pore pressure, segment bending moment and axial force during earthquake were analyzed by numerical simulation. The numerical simulation results showed that the greater the stress release degree was, the greater the initial shear stress of soil around the tunnel, the greater the deformation of soil around the tunnel during the earthquake was, the greater the excess pore water pressure was, and the greater the peak bending moment and axial force of the segment was; The greater the degree of soil disturbance was, the smaller the shear modulus of soil was, the softer the soil was, the greater the damping ratio was, the larger the deformation of soil around the tunnel during the earthquake was, the larger the excess pore water pressure was, and the smaller the peak bending moment and axial force of the segment was; The larger the range of soil disturbance was, the larger the deformation of soil around the tunnel was, the larger the excess pore water pressure was, and the smaller the peak bending moment and axial force of segment.

To study the effects of different heights of the free face, seismic intensity, subway station burial depth, and horizontal distance from the station to the free face on the subway station in liquefied soil under bidirectional earthquake action, the finite element-finite difference coupled numerical method was used to analyze the seismic response characteristics and laws of the station structure near the free face in liquefiable soils. The results showed that: the existence of the free facewould cause the horizontal displacement and rotation of the subway station, and the accumulation and dissipation of the excess pore water pressure would make the subway station float up first and then settle down; the horizontal displacement, inter-story displacement angle, and settlement after pore pressure dissipation of the structure gradually increased with the increase of seismic intensity and free face height but decreased with the increase of horizontal distance between the station and the free face and the buried depth of the structure; the existence of the free face would reduce the floating of the subway station at the end of the earthquake, and the degree of reduction increased with the increase of the free face height but decreased with the increase of the horizontal distance between the station and the free face;the internal force of the wall near the free face of the structure was smaller than that of the non-free side wall, and the internal force difference increased with the increase of the free face height; increasing the buried depth of the subway station and the horizontal distance from the free face could effectively reduce the adverse effects of the free face on the structure.

The seismic dynamic response law of ground penetrating shield technology(GPST)tunnel was studied. A three-dimensional dynamic finite element model of the ground-penetrating shield tunnel was established. The model took into account the dynamic characteristics of the Shanghai site and reasonably simulated the dynamic artificial boundary, the longitudinal and annular joints of the tunnel lining, and the soil-structure interactions. The tunnel response and site response were analyzed, and parametric analyses were performed for bolt preload, longitudinal slope, ground surcharge loading and top opening conditions. The results showed that the GPST tunnel structure could amplify the ground acceleration response, and the structural diameter deformation and acceleration response of the exposed surface section would be significantly increased. The results of the parametric analysis showed that increasing the bolt preload, increasing the longitudinal slope of the tunnel and setting a surface surcharge plate could improve the structural response; however, the top opening would significantly amplify the tunnel dynamic response.

In order to study the seismic stability of immersed tunnel, a viscoelastic-plastic stress-strain hysteresis curve was established based on the extended Masing rule, and the shear-coupled volumetric strain increment model was taken as the source term of the residual pore water pressure growth in Biot dynamic consolidation equation, an effective stress analysis method for sand liquefaction was established. The method was implemented based on the FLAC^3D computing platform. The interaction model between sandy seabed and submarine tunnel was established, and the anti-liquefaction mechanism of locked backfilling under seismic loading was studied. The results showed that the locked backfilling increased the anti-liquefaction strength of the seabed and the friction resistance, finally reduced the residual uplift distance, which effectively improved the seismic stability of the immersed tunnel.

Taking the GIL shield tunnel integrated corridor as an example, the non-linear soil-tunnel structure with and without the π-shaped bracket structure was established as a three-dimensional finite element analysis model for static and dynamic coupling, and the effect of the π-shaped bracket structure on the overall seismic performance of the shield tunnel considering staggered assembly was investigated. The results showed that the tube sheet tension at the bottom of the tunnel was significantly reduced by up to 60% after the π-shaped bracket structure was placed, and the tube sheet tension near the capping block tended to increase under large earthquakes. The acceleration response spectra at the top and bottom of the tunnel and at the π-frame structure-tunnel connection did not change significantly when the input ground shaking peak was small; as the input ground shaking peak increases, the response spectra fluctuate significantly within short periods and the overall response spectra values decreased. On the whole, the tensile damage to the concrete at the top of the tunnel structure was aggravated, while the tensile damage at the bottom was relatively light, and the tensile damage was mainly distributed at and around the tube joints. It was necessary to consider the effect of the tunnel-π-shaped support structure dynamic interaction in the seismic design of large diameter shield tunnels.

This paper focused on a practical engineering project involving a four-bore tunnel group in close proximity. Based on its features, the tunnels were simplified as spatially curved, planar curved, cambered curved, and straight tunnels. A homogeneous circular ring model was employed to establish the computational framework, enabling dynamic time-history analysis. The computational analyses conducted in this study revealed the following insights: the presence of tunnel groups had a limited impact on soil acceleration, primarily influencing soil deformation; concerning tunnel acceleration response,the acceleration in the cambered curved tunnel's cambered section surpassed other regions.This discrepancy could be attributed to the diminishing burial depth of the cambered section,signifying the influence of tunnel depth. Regarding tunnel deformation,the most significant deformation occurred at the junction of the cambered curved segment and the planar curved segment, as well as the connection between the planar curved and straight segments.It was evident that in the seismic design of curved tunnels, the connections of acute curve tunnels were identified as weak points, and the interactions among tunnel clusters under seismic effects were found to be highly complex and significant. Moreover, the interaction among tunnel groups under seismic conditions was intricate and notable. The outcomes of this research could offer valuable references for the seismic design of small-radius curved tunnels and closely spaced spatially curved tunnel groups.