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由于软土地区深部地层超孔隙水压等因素存在,调整盾构参数对土体位移的影响往往具有一定的滞后性,该时段施工参数调整效应并不完全发生在当前时段,更多影响该断面土体的后期位移。在上海软土地区盾构施工现场设置两相同断面监测土体位移,在盾构施工不同阶段调整关键施工参数,分析各参数对土体位移扰动的时效性。在盾构靠近监测断面前调整土仓压力,穿越断面时调整掘进速度,在盾尾脱出时调整注浆量。通过监测数据以及关联系数时间效应分析得,在盾构穿越断面时土体位移受前期调整的土仓压力的扰动影响,盾尾脱出时的土体位移体现穿越断面掘进速度所引起挤土效应改变,而后期固结阶段土体位移量体现出盾尾脱出时注浆量增大所带来稳定控制效应。因此,施工时不仅需关注当前土体变形,还应对参数调整后土体变形趋势预测给以足够重视,以避免因忽略滞后效应而导致事故发生。
Due to the existence of excess pore water pressure and other factors in deep strata in soft soil area, adjusting the influence of shield parameters on soil displacement often has some lag, and the adjustment effect of construction parameters does not completely occur in the current period, which affects more the section Late displacement of soil. In the construction site of Shanghai soft soil area, the same two sections were set up to monitor the soil displacement. The key construction parameters were adjusted at different stages of the shield construction, and the timeliness of each parameter on the soil disturbance was analyzed. In the shield near the monitoring section before the adjustment of soil pressure, through the cross section to adjust the tunneling speed, when the tail shield projectile adjust the amount. Through the monitoring data and correlation analysis of time effect, the displacement of soil is influenced by the disturbance of the previous adjustment of soil pressure when the shield passes through the cross-section. The soil displacement at the time of shield-tail projectile shows the change of soil-squeezing effect caused by the cross-section excavation speed , While the amount of soil displacement at the later consolidation stage shows the stable control effect brought by the increase of grouting volume when the shield tail emerges. Therefore, the construction not only needs to pay attention to the current deformation of the soil, but also pays sufficient attention to predict the deformation trend of the soil after the parameter adjustment in order to avoid the accident caused by ignoring the lag effect.