Technical Measures of Shield Tunnel Construction in Alternating Hard and Soft Rock Strata

Abstract

Subway running tunnel construction is rather difficult when using an earth pressure balance shield in alternating hard and soft rock strata for problems of dealing with full-face hard rock, upper-soft lower-hard ground, full-face soft rock, and the interface of hard and soft rock. In response to these technical problems, taking measures of theoretical analysis, indoor tests, and combined with engineering practice, the authors studied the three following matters: construction parameters for shield tunnels in different strata, the building settlement law, and countermeasures and construction technology for shield tunnels in complex strata. The main conclusions are as follows: (1) shield tunnel construction is demanding of a shield machine in alternating hard and soft rock strata such that the shield machine should have the ability to drive in hard rock and soft soil, preventing spewing, overbreak, etc.; (2) technical countermeasures and construction parameters of different strata are presented by cutting tools, driving mode, driving parameters, etc., and (3) all measuring points are affected by secondary disturbance when the rear shield passes buildings and the sedimentation value increases, which accounts for 45-66% of the final settlement.