近距离上部穿越对原有隧道沉降的影响分析

结合现场监测数据和理论分析,对隧道近距离上穿已有隧道引起的纵向变形过程及其产生原因和机理进行了分析研究。研究发现,在软土层中直径在6m左右的隧道施工,在距离原有隧道10m以外的工况下,对原有隧道纵向沉降基本不会造成影响;穿越过程中,由于土体卸载等原因,已有隧道纵向沉降主要表现为隆起,且后期变化较大;发现隧道上穿后产生的隆起值占最终值近70%,且在10￣15天后达到最大值,而后产生少量回落,大约占最终隆起值的15%。研究表明,隧道沉降变化可分为先期沉降、隧道通过时隆起、隧道穿越后一段时间内的隆起和后期沉降4个阶段,且主要变形发生在穿越以后。

Analysis of the observed longitudinal settlement of a tunnel caused by an adjacent shield tunneling on top

Combining monitoring data and theoretical analysis,the process of the longitudinal settlement of an existing tunnel caused by an adjacent shield tunneling on top is studied.It is concluded that when the cross tunneling is more than 10 meters away the settlement caused is negligible.It is also found that in the process of the tunneling on top,due to the unloading of the soil,settlement of the existing tunnel manifests mainly in the form of upheaval.This upheaval during the construction deserves close attention as it may account for almost 69% of the final settlement.The maximum settlement will be reached 10~15 days later after the crossing,and then the upheaval will be reduced by a small amount,about 15% of the final settlement.The results indicate that the settlement process can be divided into four phases: the settlement in advance,the upheaval during the crossing,the upheaval in short-term after the crossing,and the long-term settlement,with the major settlement occuring mainly after the crossing.