Study on Soil Conditioning and Key Construction Parameters of EPB TBM Advancing in Sand-Pebble Layer of Beijing Metro

Abstract

Mechanical properties of sand-pebble layer is very unstable, it is unfavourable for TBM excavation. For the reasons of poor soil conditioning and low plastic flow of muck, EPB TBM tunnel construction in sand-pebble layer of Beijing metro has exposed variety of issues: continuous dynamic earth pressure balance is hard to established, mud cake is formed frequently in earth chamber, key construction parameters such as thrust, torque, advance speed can not be controlled in reasonable scopes, which lead to low efficiency of TBM construction. Taking“Xi-Liu”of line 10 lot 11 as an research object, the mechanical characteristics of sand-pebble layer and construction problems of TBM advancing are analyzed, variety of soil conditioning measures are used for improving plastic flow of muck and minimizing construction influence induced by poor geological conditions, meanwhile contrast studies on key construction parameters before and after soil conditioning are carried out. The results indicate that effect of soil condition plays very significant roles in controlling TBM construction parameters and improving advancing efficiency.