Dynamic-Response Analysis of the Branch System of a Utility Tunnel Subjected to Near-Fault and Far-Field Ground Motions in Different Input Mechanisms

Abstract

There are few studies on the dynamic-response mechanism of near-fault and far-field ground motions for large underground structures, especially for the branch joint of a utility tunnel (UT) and its internal pipeline. Based on the theory of a 3D viscous-spring artificial boundary, this paper deduced the equivalent nodal force when a P wave and an SV wave were vertically incident at the same time and transformed the ground motion into an equivalent nodal force using a self-developed MATLAB program, which was applied to an ABAQUS finite element model. Based on near-fault and far-field ground motions obtained from the NGA-WEST2 database, the dynamic responses of a utility tunnel and its internal pipeline in different input mechanisms of near-fault and far-field ground motions were compared according to bidirectional input and tridirectional input, respectively. Generally, the damage to the utility tunnel caused by the near-fault ground motion was stronger than that caused by the far-field ground motion, and the vertical ground motion of near-fault ground motion aggravated the damage to the utility tunnel. In addition, the joint dislocation of the upper and lower three-way joints of the pipeline in the branch system under the seismic action led to local stress concentrations. In general, the branch system of the utility tunnel had good seismic performance to resist the designed earthquake action and protect the internal pipeline from damage during the rare earthquake.

Analysis of Influence Characteristics of Site Conditions on Seismic Response of Utility Tunnel

“…In practical engineering, the utility tunnel inevitably encounters complex site conditions. For example, numerous academics have researched how fault displacement affects the seismic behavior of utility tunnels [15][16][17][18]. Their findings indicate that fault displacement intensifies the damage to utility tunnels.…”

Response and failure mechanism of utility tunnel with flexible joints under reverse fault: An experimental, numerical, and analytical investigation

“…There are few researches on the mechanical behavior and theoretical analysis of the utility tunnel structure passing through the overlying soil of the active fault zone. Few studies (Jin et al, 2022; Wu et al, 2022) focus on the utility tunnel across the active reverse fault, and the research is still in its infancy. The utility tunnel structure’s failure mechanism and mechanical response have not been revealed.…”