Shaking table investigations on seismic performance of prefabricated corrugated steel utility tunnels

Highlights

• Shaking table test research on prefabricated corrugated steel utility tunnels.

• Seismic performance of the tunnel and inside brackets is analyzed and compared.

• Displacement response of the soil surface is tested and analyzed by DIC.

Abstract

A series of shaking table model tests were performed to investigate dynamic responses and damage mechanisms of prefabricated corrugated steel utility tunnels holding various brackets and pipelines. Details of the shaking table experimental setup for this kind of new utility tunnel are presented in this paper for the first time. Multiple seismic responses are measured, including the displacement of the soil surface, acceleration and strain of the utility tunnel, pipelines and brackets, as well as the acceleration and dynamic earth pressure of the test soil. The results demonstrate that the model box designed by our lab did not impose an obvious boundary effect. Displacement of the overlying soil above two sides of the utility tunnel was larger than that of the center of the model in the field nearby. The acceleration response of the structure was perfectly consistent with the surrounding soil. Dynamic earth pressures acting against the tunnel sidewall were significantly affected by the tunnel’s mass distribution under strong excitations. Response acceleration varied with different kinds of pipelines and brackets. The peak strain obtained from the suspending bracket was larger than that of the standing bracket. Different types of brackets were suitable for different applications. Both of the utility tunnel and brackets were not yielded under strong ground motions. The results provide valuable insight into the seismic performance of the shallow-buried underground steel structure and the safe design of the prefabricated corrugated steel utility tunnel.

Introduction

The utility tunnel is an underground structure that can accommodate various utility pipelines such as water, sewerage, gas, electrical power, communication lines, and heating supply. At the same time, it provides head-rooms to allow maintenance personnel and engineering vehicles to go through to perform tasks. Currently, most of the municipal pipelines in China are still directly buried underground, which is hugely inconvenient for centralized management, operation, and maintenance, resulting in the waste of natural and social resources. Due to these drawbacks, the demand for utility tunnels is growing increasingly with social and economic developments all over the world, especially in rapidly developing countries. The first utility tunnel, which was constructed in Paris in 1832, is a drainage-based utility tunnel containing some urban engineering pipelines. After that, many other countries like Russia and Japan start the construction of utility tunnels as well. However, utility tunnels appear much later in China, and the first utility tunnel with a length of 11.125 km was built in 1992 in Zhangyang Rd., Pudong new district, Shanghai (Qian and Chen, 2007). According to the Chinese government guidance (General Office of the State Council of the P.R. China, 2015), numerous utility tunnels will be built and put into use by 2020 with equivalent international standards, which indicates that the construction of utility tunnels will reach its peak period in China.

It was not until Kobe Earthquake in 1995 which caused severe damage to underground structures that made scholars fully recognized the necessity of seismic design of underground structures (Iwatate et al., 2000, Samata et al., 1997). In recent years, numerous studies have been conducted to investigate the seismic performance of different kinds of deep-buried underground structures such as mountain tunnels (Tao et al., 2015), immersed tunnels (Yu et al., 2018), culverts (Hwang et al., 2006), and subway stations (Nguyen et al., 2019). The dynamic response of a prefabricated subway station was studied both experimentally and numerically, and results shown that the deformation resistance and mechanical properties of the prefabricated subway station are excellent (Ding et al., 2019, Tao et al., 2019).

The utility tunnel, which is buried typically from 1.5 m to 2.5 m below the ground, is considered as the shallow-buried underground structure. As a fundamental infrastructure of modern society, the utility tunnel can effectively protect inside lifelines away from damages under earthquakes and actively support the post-earthquake recovery and reconstruction of cities. Moreover, the seismic behavior and damage characteristics of shallow-buried structures are quite different from those deep-buried structures (Zhou et al., 2005). Therefore, it is necessary to conduct individual seismic studies on shallow-buried utility tunnels. Until now, several studies that have been carried out on the shallow-buried utility tunnels mainly focus on cast-in-place concrete utility tunnels. For instance, Tang et al. (Tang et al., 2009) conducted a shaking table test on a cast-in-situ concrete utility tunnel with a rectangular section and partition. They found out that the tunnel and surrounding soil exhibited motion consistency under earthquakes, and some small cracks were observed at the junction of a partition wall and a bottom plate. The seismic response of pipelines was affected by the types of pipelines and supporting methods. Chen et al., 2012, Chen et al., 2010 investigated the seismic performance of a concrete utility tunnel under non-uniform earthquake excitations in both numerical and experimental ways. The results showed that the longitudinal internal force appeared in the middle of the utility tunnel, and the strain on the middle part of the tunnel was significantly larger than that at both ends.

The prefabricated corrugated steel utility tunnel has many advantages comparing with the cast-in-situ concrete one, such as the short construction period, simple construction, long service life, and environmental friendliness. A prefabricated corrugated steel utility tunnel, with a diameter of 2.7 m and a total length of 3200 m, was built in Wachau Industrial Park, Germany, in 1992, which is regarded as one of the most representative prefabricated corrugated steel utility tunnels in the world. This kind of tunnel mostly assembles by pieces of corrugated steel sheets with high-strength bolts. The corrugated steel sheets not only can highly improve the rigidity of the tunnel but also can enhance the soil-structure interaction (SSI).

Due to the positive aspects, the prefabricated corrugated steel utility tunnel becomes popular in China in recent years, as shown in Fig. 1. The upsurge in the prefabricated corrugated steel utility tunnel construction has brought out the necessity of studying and understanding their dynamic characteristics under earthquakes, but rare reports are available yet. Moreover, the current effective codes in China have not provided any guidance on the seismic design for prefabricated corrugated steel utility tunnels and the layout of inside pipelines and brackets (TCUUTE, 2015). In this paper, a series of shaking table tests were carried out to explore the seismic performance of the prefabricated corrugated steel utility tunnel, pipelines and brackets. Based on the experimental results, seismic characteristics of the utility tunnel, the surrounding soil, pipelines, and brackets were analyzed. This is the first shaking table model test on the prefabricated corrugated steel utility tunnel holding various pipelines, and experimental details discussed in this paper may be of interest to researchers in this field.