软土地区盾构隧道下穿铁路干线引起的线路沉降规律分析

软土地区盾构隧道下穿铁路干线引起的上方铁路线路沉降规律与一般情况下盾构推进引起的地面沉降规律有较大的不同。基于某地铁隧道工程实例,对隧道下穿铁路的施工期及其后续阶段的线路沉降进行观测。根据观测数据,从沉降发展的时间历程、施工各阶段沉降量所占比例和地面沉降槽的特征3个方面进行了分析研究。结果表明:此类工程的地表沉降规律特点主要是后续沉降量在总沉降量中所占比例相当大,并且其沉降达到稳定需要的时间远比通常情况要长,最终沉降量的大小几乎完全由后续沉降决定;此外,其沉降变形槽的深度和广度也更大,而且后推进的隧道上方沉降尤为显著。

Analysis on Upper Rail Settlement in Soft Ground Resulting from Shield Tunnelling across Main Railway Line

The rule of track settlement in soft ground, which is caused by shield tunnelling across the railway,is quite different from that of surface settlement caused by shield tunnelling under the common condition.Based on the observation data during construction and later stage of a certain metro tunnel engineering example,the rule of track settlement is analyzed in three aspects,including the time history,the percentage of each different stage and the feature of settlement trough.Analysis result shows that the difference of ground settlement rule between such projects and those under common condition is focused on the later stage.It requires much more time for the settlement to be steady-going and the final settlement is almost determined by later stage settlement.Furthermore,both the depth and width of the settlement trough appears deeper and wider and the ground settlement is especially obvious on the later constructed shield tunnel.