RESEARCH ON THE SEALING AND BLOCKING EFFECT OF CLAY SHOCK DURING BIOGENIC GAS-RICH GROUND TUNNELING USING SHIELD TBM

Shield tunnel construction in the biogenic gas-rich ground is a dangerous procedure. Biogenic gas is prone to penetrate shield TBM and shield tunnel through excavation cabin, slurry pipeline, tail clearance and segment clearance. It will induce combustion and explosion accidents and threaten the construction safety of shield tunnels. To seal and block the leakage of biogenic gas, clay shock is utilized to fill the gap between the middle shield and tunnel wall. In this study, aiming at the sealing and blocking problem of biogenic gas in the process of shield tunneling, a test apparatus and test method for analyzing the sealing and blocking effect of clay shock on biogenic gas have been developed. The correlation between clay shock injection thickness and gas breakdown time has been studied. The permeation mechanism of biogenic gas has been revealed. The application effect of clay shock in Sutong GIL Yangtze River Crossing Cable Tunnel has been verified. The results indicate that the gas breakdown time increases linearly with the increase of clay shock thickness. When clay shock thickness is 30 mm, the average breakdown time is 51.5 min, which exceeds the longest time required for single-ring segment assembly by 50 min and meets the requirements of the Sutong GIL Yangtze River Crossing Cable Tunnel. Field gas monitoring results indicate that when the excavation gap is filled with clay shock during shield tunnel construction, the concentration of CH₄ and CO are within the allowable range and clay shock achieves the sealing and blocking effect compared to the absence of biogenic gas prevention measures. The presented study provides a theoretical basis and technical support for the prevention and control of biogenic gas in similar engineering geological conditions.