Shaking Table Tests of Seismic Response of Multi-Segment Utility Tunnels in a Layered Liquefiable Site

Abstract

Damage to underground structures caused by liquefaction is one of the important types of hazards in the field of geotechnical engineering. Utility tunnels are the lifeline projects of cities. To ensure the sustainable and safe operation of utility tunnels over a design life of 100 years, this paper investigates the seismic response pattern of utility tunnels in the liquefied site. In this paper, shaking table tests were carried out on the utility tunnel in a layered liquefiable site. Based on the test data, the distribution law of acceleration field and pore pressure field in the model and the deformation of the soil were analyzed first. Then the soil-structure interaction, the strain and uplift of the structure were investigated. The results show that liquefaction of sand layers under strong earthquakes, resulting in seismic energy loss. The acceleration of the upper clay layer is attenuated by the seismic isolation of the liquefied soil. The utility tunnel affects the propagation of soil acceleration, which decays faster beneath the structure for the same height. The process of pore water pressure growth is a process of energy accumulation and the pore water pressure ratio curve and Arias intensity are significantly correlated. During the test, the phenomenon of sand boil appeared, and the cracks appeared on the ground surface and developed continuously. The utility tunnel in liquefied soil is lifted under the action of excess pore water pressure. There are vertical and horizontal displacement differences at the deformation joints. The strain in the utility tunnel at the stratigraphic junction is mainly influenced by the action of the bending moment, large shear deformation in the transverse section. The strain at the connection between the partition wall and the top slab is the largest and is the weak position of the structure, followed by the connection between the side walls and the top slab, and the bottom slab of the structure have a smaller strain. The results provide insights into the dynamic properties of soils and structures in liquefaction sites.