盾构掘进速度及非正常停机对地面沉降的影响

软土中盾构隧道施工不可避免地扰动周围地层，进而引起地面沉降，沉降过大时将危及邻近建（构）筑物的正常使用和结构安全。全面理解盾构隧道施工引起的地面沉降的影响因素及对沉降的准确预测，对于减少施工环境危害十分重要。考虑盾构压重后，引入Mindlin解计算盾构下卧土层中的附加应力，采用单向压缩分层总和法计算盾构下卧土层的总固结沉降，由盾构掘进速度及停机时间确定附加应力作用时间后，应用太沙基一维固结理论计算在该作用时间内的固结沉降，应用Peck公式建立了盾构下卧土层沉降与地面沉降的关系，并以杭州庆春路过江隧道地面沉降的实测验数据对上述理论进行了验证。分析表明，考虑盾构掘进速度及停机时间的地面沉降计算理论基本合理；盾构掘进速度及停机时间会对隧道施工引起的地面沉降产生显著影响；在其他施工条件相同的前提下，提高盾构掘进速度和减少停机时间有利于减少地面沉降。

Influences of shield advance rate and abnormal machine halt on tunnelling-induced ground surface settlements

Shield tunnelling in soft soils inevitably disturbs the surrounding environment and induces ground surface settlements.The serviceability and safety of the structures in the vicinity can be jeopardized in case that excess settlements are observed.A comprehensive understanding of the influencing factors of shield tunnelling induced ground settlements and an accurate settlement prediction are of great importance for minimizing the environment impacts of shield tunnelling.Taking the load of the shield into account,the Mindlin’s solution is introduced to calculate the additional stress in soils beneath the shield,and the layer-wise summation method is applied to calculate the final one-dimensional consolidation settlement.The duration of additional stress in soils relies on the shield advance rate and its halt time,and the corresponding consolidation settlement can be calculated using the Terzaghi’s one-dimensional consolidation theory.Finally,the relationship between consolidation settlements and ground surface settlements is established by Peck equation.The theory is verified by in-situ monitored ground surface settlements in construction of Hangzhou Qing-chun Road cross-river tunnel in China.These studies show that the shield advance rate and machine halt duration have a significant impact on the ground surface settlements,and the increase in shield advance rate and decrease in machine halt duration favors the settlement control.