软土地区狭长型深基坑开挖引起深层土体变形分析

Analysis on the Deep Soil Deformation Induced by Construction of Narrowlong Excavation Pit in Soft Ground Area

在深厚软土地层中开挖狭长型深基坑将对周边环境产生较大影响。文章通过建立三维有限元模型,采用HS-Small小应变本构模型模拟狭长基坑开挖过程软土变形特性,分析在狭长基坑开挖过程紧邻土体深层位移发展规律。结果表明:邻近土体竖向及水平位移对基坑开挖深度敏感,随着基坑开挖深度的增加而增大;水平位移发展曲线呈V形或弓形形态,最大水平位移基本与开挖深度一致;开挖深度以上土体发生沉降变形,而开挖深度以下土体由于基坑卸荷发生隆起变形;当拆除支撑而不及时施作新梁板结构时,将减弱整体支护刚度,引起地层水平位移与沉降。由于基坑空间效应影响,基坑长边测点水平及竖向位移最大,短边测点次之,坑角最小。

Construction of narrow-long excavation pits in deep and thick soil ground has significant impacts on surrounding environments.A three-dimensional finite element model is established,the characteristics of soft soil deformation are simulated by a HS-Small constitutive model and the law of displacement development of adjacent deep soil is studied during construction of the narrow-long excavation pit.It is found that both vertical and horizontal displacements of adjacent soil mass are sensitive to the depth of excavation pit and they increase with an increase of excavation depth;the curve of lateral displacement of soil mass is of V or arch form and the position of the maximum lateral displacement is in accordance with the excavation depth;settlements are observed at the soil mass above excavation depth and heaves are observed at the soil mass below the excavation depth due to unloading effect of excavation;the suport stiffness decreases if support is removed and new beam is not constructed immediately to replace it and this will result in lateral and vertical displacements of stratum.Due to the excavation spatial effect,the orders of lateral and vertical displacements of the monitoring points are the long side,short side and pit corner of excavation pit in terms of displacement magnitude.