一种跨海地铁隧道盾构始发端头加固方法

摘要

海滨地区的地下水贮藏丰富,且常常同海水存在水力联系.为了降低跨海地铁隧道的盾构始发风险,以厦门地铁3号线跨海区间工程为例,遵循"先封闭降水,后土体加固"的技术思路,提出了一种素混凝土地下连续墙与高压旋喷桩相结合的盾构始发端头加固方法,并针对该加固方法给出了配套的施工降水及洞门防水设计方案.实践表明: 该方法在海滨富水砂层可以有效阻断地下承压水,保障土体加固效果,降低盾构始发风险.此外,为防止素混凝土地下连续墙在盾构推力作用下发生脆性破裂,影响施工安全,利用FLAC3D数值模拟软件对不同盾构推力作用下的墙体应力状态进行分析,得出保证素混凝土地下连续墙完整性的盾构有效推力控制范围值.%The groundwater in coastal area is rich and always in contact with the sea, which brings a great risk to the shield launching of sea-crossing metro.Taking sea-crossing section on Xiamen Metro Line No.3 for example, an end soil reinforcement method which combines high-pressurized jet grouting pile and underground plain concrete diaphragm wall is put forward, in accordance with the technical idea of "sealing and dewatering first and then soil reinforcement".Meanwhile, corresponding programs of construction dewatering and tunnel entrance sealing are proposed.The construction practice shows that the above-mentioned method can effectively block the hydraulic connections between tunnel and sea;thus ensuring the soil reinforcement quality and reducing the risk of shield launching.In addition, the stress state of the underground diaphragm wall under different shield trusting forces is analyzed by numerical simulation software FLAC3D;and then effective control range of shield thrusting force which can guarantee the integrity of underground plain concrete diaphragm wall is obtained, so as to prevent nonplastic fracture of underground plain concrete diaphragm wall.