Deterioration and Cavity of Surrounding Rocks at the Bottom of Tunnel Under the Combined Action of Heavy-Haul Load and Groundwater: An Experimental Study

Zheng Li,Kunping Chen,Weiwei Huang,Ziqiang Li,Xinsheng Wang

doi:10.3389/feart.2021.779578

Abstract

In China, the first tunnel was built in accordance with the 30-ton heavy-haul railway standard. Based on the change in water and soil pressure obtained from long-term on-site monitoring, the cavity mechanism of the surrounding rock at the bottom of a heavy-haul railway tunnel under rich water conditions was explored in this study. The cavity characteristics and degradation depth of the three types of surrounding rock under different axial loads and hydrodynamic pressures were analyzed through laboratory tests. The structural defects at the bottom of the tunnel and local cracks in the surrounding rock were determined to provide a flow channel for groundwater. The dynamic load of heavy-haul trains causes groundwater to exert high hydrodynamic pressure on the fine cracks. The continuous erosion of the bottom surrounding rock leads to a gradual loss of surrounding rock particles, which would further exacerbate with time. The cohesive soil surrounding rock is noticeably affected by the combined action of heavy-haul load and groundwater in the three types of surrounding rock, and the surrounding rock cavity is characterized by overall hanging. In the simulation experiment, the particle loss of the surrounding rock reached 1,445 g, which is 24.2% higher than that of the pebble soil surrounding rock and 40.8% higher than that of sandy soil surrounding rock. The findings of this study could be helpful for developing methods for defect prediction and treatment of heavy-haul railway tunnels.

Highlights

At present, heavy-haul railway transportation has become one of the major means of transportation of global trade goods
According to the dynamic load of a 300-kN heavyhaul train obtained by the excitation test, combined with the dynamic similarity ratio of the laboratory test, the excitation force was increased by 10 times as that applied to the surface of the tunnel bottom structure at 100 kPa
The characteristics and formation mechanism of the cavity and degradation of the surrounding rock at the tunnel bottom under the combined action of heavyhaul train and groundwater were simulated for three types of surrounding rocks: pebble soil, clay soil, and sandy soil

Summary

Introduction

Heavy-haul railway transportation has become one of the major means of transportation of global trade goods. Measuring Point Arrangement To measure the distribution and variation in the water pressure and contact pressure of the surrounding rock of the tunnel basement under the long-term load of the heavy-haul train, the measuring points, as shown, were symmetrically arranged on the surface of the bottom surrounding rock, arch foot, bottom of the side ditch, bottom of the track, and center of the line (Goh et al, 2018; Zhang et al, 2020a).

Results

Conclusion