地铁暗挖施工引起的管线与地层沉降关系研究

依托北京地铁4号线公益西桥站工程,建立结构-地层-管线三维弹塑性数值模型,基于管线周边地层沉降及地表沉降实测数据分析,研究西南出入口暗挖施工上方管线周边地层变形规律。通过现场实测数据、数值模拟及经验公式计算结果综合对比,分析了管线刚度对地层变形抵制作用的影响。研究表明:管土相对刚度小于0.18时,管线与土体沉降差小于5%,可用经验公式计算出的管线轴线处地层沉降代替管线沉降。随管线刚度的增大,管线对土体变形的抑制作用逐渐增强,沿深度方向地层沉降量增大速率减小,并会出现负增长,甚至出现地层沉降小于地表沉降的情况。通过对数值计算结果的拟合分析,提出了刚性接头管线与地表沉降比和管土相对刚度的经验公式。工程实例应用结果表明,计算值与实测值偏差小于4%,验证了该方法的适用性。

Relationship between the surface subsidence and the pipeline displacement induced by metro tunnel construction

A 3D elastoplastic numerical model is developed for the structure-soil layers-pipeline system in the Gongyixiqiao metro station project of Beijing metro line 4, and used to analyze the deformation of pipeline and its surrounding soil, based on the measured displacement data. By combing the field monitoring data, numerical simulations and empirical formulations, the effects of pipeline stiffness on ground deformation are analyzed. It is shown that as the soil-pipe stiffness k is less than 0.18, the differential soil-pipe settlement is less than 5%, and the empirical formulation can be used to calculate the soil settlement at the level of pipeline axis. With the increase of pipeline stiffness, the pipeline can constrain the ground movement more significantly, resulting in a reduction of the growth rate of ground settlement or even a negative growth so that the surface settlement can even exceed the ground settlement. By a fitting analysis of the numerical results, a method is proposed for estimating the maximum pipeline settlement for rigidly jointed pipelines, which is based on the soil-pipe stiffness and tunnel-induced ground surface settlement. The method has been used to calculate an actual project settlement, and the difference between the calculated and measured values is found to be less than 4%, showing the applicability of the proposed method.