盾构隧道下穿既有车站桩筏基础影响分析及施工控制——以杭州地铁5号线盾构隧道下穿杭州南站站房工程为例

Influence of Shield Tunnel of Hangzhou Metro Line 5 on Pile-Raft Foundation of Existing Hangzhou South Railway Station and Construction Control Technology

为解决盾构隧道下穿既有车站桩筏基础影响分析及施工控制问题,依托杭州地铁5号线盾构隧道下穿杭州南站工程,结合数值模拟和实测数据对盾构隧道与桩筏基础的相互作用进行分析,研究穿越过程中地表和既有车站沉降及桩基变形规律,并通过与实测数据对比验证数值模拟的准确性,最后提出针对性的施工控制措施。结果表明:1)在双隧道中心线位置设置桩筏基础能够有效地降低车站底板下方土体沉降和施工引起的二次扰动;2)隧道下穿工程中邻近桩基础位移、弯矩和剪力的峰值位于隧道底部平面,可根据此特点制定合理的加筋、支护方案;3)隧道下穿淤泥质黏土地层时,可视地层损失率为2%进行保守设计,实际施工中可通过二次跟踪注浆来降低地层损失率;4)调整盾构姿态并在盾构上方压注速凝浆液,可有效地控制盾构隧道上浮。

To investigate the impact of shield tunnel on pile-raft foundation of existing railway station and the constuction control technology,a case study is conducted on a shield tunnel of Hangzhou metro line 5 crossing underneath Hangzhou south railway station.Then,the interaction between the shield tunnel and the pile-raft foundation of the existing railway station is analyzed through numerical simulation and measured data.Moreover,the deformation of surface and the existing station and the deformation of the pile foundation are examined,and the numerical simulation results are validated by measured data.Finally,corresponding construction control technologies are proposed.The results reveal the following:(1)The pile raft foundation at the center line of the twin-tunnel can effectively reduce the soil settlement under the station floor and the secondary disturbance caused by construction.(2)During shield tunnel underpassing,the peak values of displacement,bending moment,and shear force of adjacent pile foundation appear at the bottom plane of the tunnel,which can provide reference for reinforcement and support scheme.(3)When the tunnel passes through muddy clay layer,the conservative design can be carried out according to the formation loss rate of 2%.In the actual construction,the formation loss rate can be reduced by secondary tracking grouting.(4)By adjusting the shield posture and injecting quick setting slurry above the shield,the upward floating of the shield tunnel can be effectively controlled.