明挖隧道基坑的回填沉降影响因素分析

Analysis of Factors Affecting Backfill Settlement of a Cut and Cover Tunnel

城市大型明挖隧道基坑常因施工作业面限制出现工后沉降较大的问题。依托软土地区大型明挖隧道基坑回填的工程实例,利用Midas GTS岩土有限元软件,对比分析了隧道断面形式和回填材料参数对基坑回填后的地表沉降及隧道结构变形的影响规律。研究分析得出:基坑回填后的地表沉降变形主要受回填材料自身的压缩性影响,即回填材料的压缩性越大,地表沉降越大;影响隧道结构沉降变形的主要因素是回填材料的重度以及隧道下方软弱地层厚度。因此,对于明挖隧道基坑,需要根据地表沉降和结构沉降需求,选择合适的方式处理回填土料。

Large post construction settlement is usually observed at the excavated area of a cut and cover tunnel excavation area.This paper presents an excavation of a cut and cover tunnel in soft soil area.The effect of the shape of the tunnel cross section and the backfill material on the settlement of the excavated area and the structural deformation of the tunnel are numerical investigated by using MIDASGTS geotechnical commercial software.Results show that the ground settlement after the completion of backfilling is mainly affected by the compressibility of the backfill material itself,that is,the greater the compressibility of the backfill material,the greater the surface settlement.The main factors that affecting the settlement and deformation of the tunnel structure are the unit weight of the backfill material and the thickness of the weak stratum below the tunnel.Therefore,for the excavation of the cut and cover tunnel,it is necessary to select an appropriate method for the backfill soil in accordance with the allowable deformation criteria for backfill material and for the tunnel strucutre.