深厚淤泥质土层深基坑变形特性研究

Research on Deformation Characteristics of Deep Foundation Pit in Deep Silty Soil Layer

为解决因淤泥质土层较厚导致的基坑变形大和地表沉降不均等问题,依托湖北交投实业总部深基坑工程,通过数值仿真分析,对比两种不同内支撑布置方式下的变形规律,并研究深厚淤泥质土层对基坑变形的影响。结果表明:开挖深度较浅且未设置内支撑时,围护结构整体表现为“悬臂梁式”变形形态;随开挖深度增大及内支撑逐步施作,围护结构主要表现为中部向坑内凸出的“鼓肚形”变形形态。受淤泥质粘土层影响,围护结构变形与地表沉降变化值显著增加。基坑开挖至坑底时,在角部设置两道内支撑方案最大位移发生在0.77H位置(H为基坑开挖深度),为43.2 mm;在轴对称处设置一道内支撑时最大位移为47.48 mm。两种方案下的地表沉降最大值均基本稳定在0.6H位置,分别为31.50 mm、31.24 mm。当基坑进行两次拆换撑操作时,围护结构及地表沉降变形值有一定幅度增大,尤其在第一道支撑拆除后,建议施工过程中做好监测及相应控制措施。

In order to solve the problems of large deformation of the foundation pit and uneven surface settlement caused by the thick silty soil layer in the deep foundation pit project,this paper relies on the deep foundation pit project of the Hubei Investment Industrial Headquarters and compares the two deformation laws of different internal support arrangements through numerical simulation analysis,and also studies the influence of the deep silty soil layer on the deformation of the foundation pit.The research results show that when the excavation depth is shallow and internal supports are not set,the overall deformation of the envelope structure appears as a“cantilever beam”deformation form.With the increase of the excavation depth and the gradual implementation of the internal support,the deformation of the enclosure structure is mainly manifested as a“bulging”deformation form in the middle that protrudes into the pit.Affected by the silty clay layer,the deformation of the enclosure structure and the change in surface settlement increase significantly.When the foundation pit is excavated to the bottom of the pit,the maximum displacement occurs at 0.77H(H is the excavation depth of the foundation pit)when two internal supports are set at the corners,which is 43.2 mm;the maximum displacement is 47.48 mm when one internal support is set at an axisymmetric position.The maximum surface subsidence of the two schemes is basically stable at the position of 0.6H,which is 31.50 mm and 31.24 mm,respectively.When the foundation pit is dismantled and replaced twice,the deformation value of the surrounding structure and ground settlement will increase to a certain extent,especially after the first support is dismantled.It is recommended that monitoring and corresponding control measures be taken during the construction process.