Effective method for adjusting the uplifting of shield machine tunneling in upper-soft lower-hard strata

Abstract The control and treatment of excessive uplifting of a shield machine during tunneling in the upper-soft lower-hard strata is challenging. This is because buoyancy of the shield machine is induced by the gap between the shield machine and the ground, and the upper ground has less resistance than the lower ground in the upper-soft lower-hard composite strata. In this paper, a new method for adjusting the excessive uplifting of a shield tunnel machine is proposed. This method utilizes a special drill beneath the shield machine’s cutter head that operates on the middle shield machine position and can result in subsidence of the ground under the heavy weight of the shield machine. Based on this new technique, a case study of the excessive uplifting of a shield tunnel machine in the line No. 3 of China’s Nanning Metro is presented. The shield tunnel machine’s maximum uplifting amount of 118 mm was successfully corrected, and the treatment processes had no influence on the surrounding environment. The correction method for the excessive uplifting of shield machines proposed in this study can provide a reference for future projects with similar conditions.