圆形基坑地下连续墙结构宜按照空间结构计算,如三维有限元分析或部分规程规定了考虑圆形拱效应的平面竖向弹性地基梁法,计算较复杂,影响因素较多。本文通过实际工程案例,根据基坑实测结果,从地墙环向刚度、接缝泥皮厚度等方面分析了地连墙变形机理和影响。结果表明:圆形地连墙环向围压作用下径向水平变形主要由泥皮压缩变形和混凝土压缩变形产生;根据泥皮压缩和混凝土压缩模型建立圆形地连墙径向水平位移计算公式,围压较小时,地连墙环向刚度主要表现为泥皮压缩刚度几乎可以忽略;常规平面竖向弹性地基梁法和有限元计算中墙体的等效环向刚度在地墙变形前即施加,计算结果偏小,基坑偏不安全。本文根据理论分析和实测结果对比,提出平面竖向弹性地基梁法简化计算方法,计算中根据接缝压缩量或墙体变形量动态化考虑地连墙环向刚度更合理。
Circular excavation diaphragm wall structure should be computed in accordance with the spatial structure, such as three-dimensional finite element analysis or certain specifications of the plane vertical elastic foundation beam method, considering the circular arch effect. The calculation is rather complex, with numerous influencing factors. In this paper, the deformation mechanism and influence of the ground connecting wall are analyzed from the aspects of the circumferential stiffness of the ground wall and the thickness of the joint mud skin based on the actual engineering case and the measured results of the foundation pit. The results indicate that: The radial horizontal deformation of the circular ground wall under the circumferential confining pressure is mainly attributed to the compression deformation of mud and concrete. A formula for calculating the radial horizontal displacement of the circular ground wall is established based on the mud compression and concrete compression models. When the confining pressure is low, the annular stiffness of the ground wall is mainly manifested as the mud compression stiffness, which can be nearly disregarded. In the conventional beam method and finite element calculation, the equivalent circumferential stiffness of the wall is applied before the deformation of the ground wall, and the calculation result is too small, leading to an unsafe foundation pit. In this paper, based on the comparison of theoretical analysis and measured results, a simplified calculation method of the beam method for the plane vertical elastic foundation is proposed. In the calculation, it is more rational to consider the toroidal stiffness of the ground connecting wall according to the dynamic joint compression or wall deformation.
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