复合地层双模盾构风险分析与针对性设计

为解决富水圆砾—泥岩复合地层采用双模盾构的适应性设计问题，依托南宁市轨道交通5号线五一立交站—新秀公园站隧道工程，针对穿越邕江、下穿浅基础建筑物、圆砾—泥岩复合地层中地表沉降和刀盘固结泥饼等施工风险，提出泥水/土压双模盾构结构和功能系统的针对性设计。在结构设计方面，双模盾构增设气垫仓稳定泥水压力，并配合排浆口优化设计实现了对地层沉降的稳定控制；加设中心面板和扭腿冲刷及“P0泵小循环”系统降低泥饼形成概率；优化的螺旋输送机设计减小喷涌压力，与邻近线路相比，过江段掘进速率提高近1倍。在功能性系统方面，实现泥水和土压2种排渣体系的快速转换；推进系统总推力达39 910 kN，满足不同掘进状态的需要；通过注浆系统与合理掘进参数实现对地表沉降的严格控制。

Analysis of Risks and Targeted Design of Dual modeShield in Composited Strata

Adaptive design of dual modeshield in water rich gravel mudstonecomposited strata is of great significance. As a result, the targeted designsof structure and functional system of slurry/earth pressure dual mode shield used in Wuyi Interchange station Xinxiu Park station on Nanning Rail Transit Line No. 5 are putforward according to the construction risks such as crossing through YongjiangRiver, crossing underneath buildings with shollow foundations, surfacesettlement induced by shield boring in gravel mudstonecomposited strata, and muck cake on cutterhead. As for structural design, theair cushion chamber is used to stabilize slurry pressure, and the slurrydischarge port is optimized so as to realize the stable control of surfacesettlement. The brush and P0 pump circulation systems are set on central paneland bracket to effectively reduce the mud cake phenomenon. The design of screwconveyor is optimized to reduce the gushing pressure, and compared with theadjacent lines, the boring speed of the river crossingsection is increased by nearly one time. As for functional system, muckingsystem conversion between slurry and earth pressure dual mode is realized, the total thrust of the propulsion system reaches39 910 kN, which can meet relevant requirements under different workingconditions, the surface settlement is strictly controlled according to groutingsystem and rational tunneling parameters control.