Shaking Table Tests for Seismic Response of Orthogonal Overlapped Tunnel under Horizontal Seismic Loading

Honggang Wu,Tianwen Lai,Hao Lei,Ma Jianjun

doi:10.1155/2021/6633535

Abstract

This paper presents the seismic dynamic response and spectrum characteristics of an orthogonal overlapped tunnel by shaking table tests. First, a prototype of the engineering and shaking table test device, which was used to design details of the experiment, was developed. Then, the sensors used in the test were selected, and the measurement points were arranged. Subsequently, the Wenchuan seismic wave with horizontal direction in different peak ground accelerations was inputted into the model, followed by a short analysis of the seismic response of the overlapped tunnel in the shaking table test as well as the distribution of the peak acceleration. Throughout the studies, the model exhibited obvious deformation stages during the seismic wave loading process, which can be divided into elastic, plastic, plastic enhancement, and failure stage. In particular, the time- and frequency-domain characteristics of the key parts of the tunnel were discussed in detail by using the continuous wavelet transform (CWT) based on the Morlet wavelet as the basis function. We found that the acceleration response was more intense within 25–60 s after the seismic wave was inputted. Furthermore, owing to “the superposition effect,” the seismic response at the crown of the under-crossing tunnel was stronger than that at the invert of the upper-span tunnel. The low and medium frequencies in the transformation of small scales (5–20) significantly affected the overlapped tunnel. These results elucidate the seismic dynamic response of the overlapped tunnel and provide guidance for the design of stabilizing structures for reinforcing tunnels against earthquakes.

Highlights

With the development and utilization of underground space, three-dimensional intersections or close constructions between tunnels inevitably occur [1,2,3]
Theoretical analysis, numerical analysis, and physical modelling are commonly used for evaluating the seismic performance of underground structures, which have been studied by many researchers. e pioneering study in the theoretical analysis of the seismic response of the tunnel was performed by St
The seismic waves in the main frequency bands should be avoided to resonate with the structure, providing relevant theoretical references for engineering practice. erefore, to study the seismic response and spectral characteristics of the overlapped tunnel in more detail, we introduced wavelet transform (WT), a mathematical tool that can characterize the local characteristics of seismic waves in the time-frequency domain

Summary

Introduction

With the development and utilization of underground space, three-dimensional intersections or close constructions between tunnels inevitably occur [1,2,3]. The overlapped tunnel, which differs from the conventional single tunnel, is relatively complex under the action of seismic loading because of its relatively ambiguous load and sensitivity to the surrounding environment. Theoretical analysis, numerical analysis, and physical modelling are commonly used for evaluating the seismic performance of underground structures, which have been studied by many researchers. E pioneering study in the theoretical analysis of the seismic response of the tunnel was performed by St. John and Zahrah [7], and their theory is still used in subsequent studies [8,9,10,11]. Ey presented an advanced review of the current understanding of the seismic behavior of tunnels According to their theory, the seismic performance and damage characteristics of tunnel structures differ from those of aboveground structures. Numerical simulations of the seismic response of double-deck overlapped tunnels of subways

Methods

Results

Conclusion