Abstract
In order to explore the influences of fault dislocations on tunnel stability under seismic action, a nonlinear dynamic simulation method for the rock–fault contact system is proposed. First, considering the deterioration effect of seismic action on the ultimate bearing load of the contact interface between rock mass and fault, a mathematical model is established reflecting the seismic deterioration laws of the contact interface. Then, based on the traditional point-to-point contact type in a geometric mesh, a point-to-surface contact type is also considered, and an improved dynamic contact force method is established, which considers the large sliding characteristics of the contact interface. According to the proposed method, a dynamic finite element calculation for the flow of the rock–fault contact system is designed, and the accuracy of the method is verified by taking a sliding elastic block as an example. Finally, a three-dimensional (3D) calculation model for a deep tunnel through a normal fault is built, and the nonlinear seismic damage characteristics of the tunnel under horizontal seismic action are studied. The results indicate that the relative dislocation between the rock mass and the fault is the main factor that results in lining damage and destruction. The seismic calculation results for the tunnel considering the dynamic interaction between the rock mass and the fault can more objectively reflect the seismic response characteristics of practical engineering. In addition, the influences of different fault thicknesses and dip angles on the seismic response of the tunnel are discussed. This work provides effective technical support for seismic fortification in a tunnel through fault.
Highlights
A large number of tunnel projects in China that are under construction or have already been built, are located in earthquake-prone areas, especially in the southwest
The “5.12” Wenchuan earthquake indicated that tunnels with good engineering geological conditions show good seismic performance, while tunnels with complex geological conditions, including major changes of strata or poor rock properties, are more vulnerable to seismic damage
Before the seismic action is applied, the discontinuity of the finite element model can be realized by adding common nodes on the contact interface between the rock mass and the fault
Summary
A large number of tunnel projects in China that are under construction or have already been built, are located in earthquake-prone areas, especially in the southwest. Engineering practice indicates that once an earthquake occurs, relative dislocation is produced between the rock mass and the fault, which can lead to irreparable damage to the tunnel and can affect its normal operation. This makes rescue work in the earthquake area much more difficult. Model tests and numerical simulations are the main methods adopted to study the dynamic response laws of the tunnel through fault under seismic action. The traditional dynamic contact force method assumes a small sliding displacement, which is clearly not perfect when simulating large dislocations between rock masses and faults. The simulation results for the engineering case indicate that the proposed method reflects the nonlinear seismic damage characteristics of the tunnel through fault reasonably well
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