软土地区盾构掘进速度对地层扰动现场试验研究

针对上海软土地区盾构隧道工程，在盾构穿越监测断面全过程调整掘进速度，观察监测断面的水、土压力以及地层稳定性变化。根据实测并结合土体固结比、承压水等地层土性影响，运用土体扰动机制综合评定掘进速度改变的影响规律。分析表明，盾构在软土地区4倍直径(D=6.2 m)埋深地层中施工，在盾构土舱压力、注浆量等参数均不变的条件下，仅调整千斤顶推进速度变化对土体压力及变形的扰动效应有较大影响。盾构推进速度降低会使水、土压力的扰动空间范围减小、扰动所产生的压力增量减小，也使地表隆沉变化值更稳定。相应变化值由埋深和推速降低比例决定。试验为今后判断软土地区4D埋深盾构掘进速度扰动效应提供参考。

Experimental study of disturbance caused by the advancing speed of shield tunneling in soft soil

In view of shield tunnel projects in soft soil area of Shanghai, the advancing speed of the shield machine is adjusted, and the water pressure, soil pressure and strata stability are observed in the whole process of the shield crossing the monitoring section. According to the measured soil consolidation ratio, the pressure of artesian water and other strata soil properties, the influences of the varied advancing speeds are comprehensively evaluated by the mechanisms of soil disturbance. The analysis indicates that the shield tunneling in soft soil area is approximately 4 times of the diameter (D=6.2 m). By keeping the chamber earth pressure and grouting amount invariant in the shield advancing process, the change of the hoisting speed of the jack to great extent influences the soil pressure and deformation. Reducing the advancing speed results in the decrease of the disturbance range of water and earth pressures and then the disturbance is generated by the pressure increment, but leads to more stable values of the induced surface heave. The corresponding change value is determined by the ratio of depth to the advancing speed. Experiment results provide a certain valid reference to ensure the effect from the shield speed of the jack at the depth of 4D.