黄土地层地铁盾构施工地表变形规律预测研究

Study on Prediction of Surface Deformation during Shield Construction of Subway in Loess Stratum

研究目的:西安地铁是我国首次在黄土地层修建地铁,黄土地层具有湿陷性等特殊的物理力学特性,盾构是西安地铁隧道的主要施工方法之一,但有关西安地铁盾构施工诱发的地表沉降特性预测的研究成果目前还很少,急需开展黄土地层地铁盾构施工诱发的地表变形规律预测方法研究,目的是为盾构施工地表沉陷监测方案的制定和盾构施工参数的确定提供理论依据,以保证隧道盾构安全施工。研究结论:通过理论预测计算得到的沉降值与西安地铁某区间隧道的地表沉降实测数据进行了对比分析,研究结果表明:(1)给出的地表沉降预测公式预计的地表沉降趋势和数据与实测值基本一致;(2)盾构施工时,正面附加推力可以维持开挖面前方土体的稳定,但正面附加推力的大小对地表竖向位移量的大小会产生影响;(3)盾构施工时,影响地表竖向位移因素很多,而盾尾间隙的大小对地表竖向位移影响最大;(4)盾构施工时,地表沉降量随着距隧道轴线距离的增加变形量逐渐减小,在隧道轴线上方变形最大。

Research purposes： The Xihn subway is the first subway built in loess stratum in China, and the loess has some special physical and mechanical properties such as collapsibility. The shield construction is one of the main methods for construction of subway tunnel, but there is a little research on prediction of the feature of surface deformation induced by shield construction. So it is urgent to do the study on prediction of the features of the surface deformation induced by shield construction in loess stratum for the purpose of offering some theoretical basis for working out the monitoring program for the surface deformation and determining the shield construction parameters to ensure the construction safety of the shield tunnel. Research conclusions：The comparative analysis of the theoretical forecast computation and the measured data on the surface deformation of one interval tunnel of Xihn subway was made and the results showed： （1） The predicted surface deformation tendency and data calculated by the prognostic formula was basically consistent with the actual value. （2） During shield construction, the front additional pushing force could remain the the stability of the soil in front of the excavating surface and the big or small of the the front additional pushing force could influence the big or small of the ground vertical displacement. （3） During shield construction, there were lots of factors to influence the ground vertical displacement, but the big or small of the gap of the shield tail had the biggest influence on the ground vertical displacement. （4） During shield construction, the ground settlement decreased with the increase of the axial distance of the tunnel, and deformation above the the tunnel axial was the biggest.