圆形地下连续墙场地地震反应的简化计算方法

A simplified method for seismic response analysis of site with circular diaphragm wall

首先将水平地震荷载作用沿环向展开为傅立叶级数,利用沿圆周法向和切向两个方向的正交性,再将水平地震荷载转化为一致横向荷载组合,使三维求解问题转变为一系列旋转子午面上二维问题的叠加,进而提出圆形地下连续墙场地地震反应的简化计算方法。之后,采用等效线性化方法来考虑土体非线性性质,进一步将非线性地震反应问题转化为线性问题求解。通过对比简化方法结果与三维方法结果,验证了简化方法的实用性和可靠性。比较结果表明,简化方法缩减了模型规模,极大提高了计算效率。最后对某超大直径圆形地下连续墙场地进行了地震反应分析,与场地中不设连续墙的自由场结果相比,发现圆形墙体的围束效应使得基坑底部的加速度峰值有所增大,而对远离墙体的地表土层的地震反应影响很小。

First, the horizontal seismic loads were expanded into the Fourier series in the circumferential direction. Considering the orthogonality between the normal and tangential direction on the circumference, the horizontal seismic loads were then transformed into combination of uniform distributed lateral loadings. In this way, the simplified solving method was proposed for the three-dimensional problem reduced to a series of two-dimensional problems. The equivalent linearity method was used to deal with soil nonlinearity, so the nonlinear seismic problem was transformed into linear problem. The practicability and reliability of the simplified method were verified by comparison between the results of simplified model and 3-D model. The results show that the model size is reduced and the computational efficiency is greatly improved by the proposed method. Finally, simplified method was used to analyze the seismic response of foundation site with super large diameter circular diaphragm wall. Compare with the results of the site without wall, the peak acceleration of the pit bottom is increased owing to the confinement effect of wall, and the influence to ground surface far from the wall is very little.