Instability of Large Diameter Slurry Shield Tunnelling Attitude in Highly Viscous Clay Strata and Treatment Measures
(1. China Railway Tunnel Stock Co., Ltd., Zhengzhou 450000; 2. School of Civil Engineering, Central South University,Changsha 410075; 3. China Railway Development and Investment Group Co., Ltd., Kunming 650200)
Abstract：
In order to solve the problems of low tunnelling efficiency and difficulty in control of the shield attitude that may occur when the shield tunnelling machine operates in highly viscous clay strata, in this study, based on a cross-river tunnel project with a large diameter slurry shield tunneling machine and focused on the problems of abnormal excavation and attitude instability, the causes for attitude instability during tunnelling in highly viscous clay strata are discussed in combination with the tunnelling parameters and the changes of the strata within the tunnelling section, and corresponding treatment measures are proposed and implemented. The results show that: (1) the abnormal section of shield tunnelling coincides with the distribution of highly viscous clay strata, and the change in geological conditions is the fundamental cause for the attitude instability of shield tunnelling; (2) The actual frontal resistance of the cutterhead when the shield tunnelling machine operates in highly viscous strata is similar to the theoretical calculation results, while the actual frictional resistance between the shield housing and the strata is far higher than the theoretical value, and no guniting and water seepage occurs after opening the radial grouting holes on the shield housing, so it is inferred that the direct cause of the abnormal shield tunnelling and attitude instability of the shield machine is the continuous adhesion and accumulation of highly viscous clay particles on the outer surface of the shield housing to form dense clay inclusions, which changes the interaction state between the shield housing and the strata; (3) By drawing inspiration from the disposal measures of dispersant mud cake, the protocol that a dispersant is injected into the radial grouting holes on the shield housing is used to remove the clay inclusions outside the shield housing. The dispersant solution is selected through indoor clay dispersion tests; (4) After continuous in? jection of dispersant outside the shield housing for a period of time, the total thrust of the shield machine quickly decreases by about 30,000 kN with the continuous growth of the burial depth of the tunnel. As the shield tunnelling slows down, the shield attitude is continuously adjusted. After reopening the radial grouting holes on the shield housing, guniting occurs, indicating that the dispersant can effectively peel off the clay coverings on the outer surface of the shield housing.
WANG Yanhui1 ZHOU Tianshun1 HU Junshan1 CHEN Haiyong2,
3 SHI Chenghua2 PENG Yu1 WANG Zuxian2
.Instability of Large Diameter Slurry Shield Tunnelling Attitude in Highly Viscous Clay Strata and Treatment Measures[J] MODERN TUNNELLING TECHNOLOGY, 2023,V60(5): 213-223
2023, Vol. 60 