变截面搅拌桩加固路堤下成层软弱地基数值模拟

Numerical simulation of variable diameter deep mixed columns-treated layered soft ground under highway embankment load

为了经济、有效地处理软土层位于中间的成层软弱地基,提出了变截面搅拌桩加固方法,在高压缩性土层中采用较高的桩体置换率,在中等压缩性土层中采用较低的桩体置换率,从而形成桩体置换率随土层性质变化的成层复合地基。通过三维数值模拟,对变截面搅拌桩加固路堤荷载下成层软弱地基的性状进行了研究,不同设计参数的变截面搅拌桩复合地基的等效面积置换率(体积置换率)相同,但是大小桩径比(扩大头直径/小桩直径,D/d)不同。数值模拟结果表明:变截面搅拌桩复合地基的地表沉降与其大小桩径比密切相关,存在最优的桩径比使得复合地基地表沉降最小,但是路堤坡脚处复合地基最大水平位移受大小桩径比的影响较小。

The variable diameter deep mixing method is proposed to economically and efficiently treat a layered soft ground, where the soft layer is at the middle depth. A relatively high column replacement is used for the high compressive soil layer and a relatively low column replacement is used for the medium compressive soil layer, resulting in a layered composite foundation with the column replacement varying with the soil layer. 3D numerical analysis is carried out to investigate the performance of the layered soft ground treated by variable diameter shaped deep mixed columns with different design parameters. The different numerical cases of variable diameter shaped deep mixed columns-treated layered soft ground have the same equivalent area replacements(volume replacements), but different column diameter ratios(D/d). The results indicate that the settlement at the ground surface is remarkably affected by D/d and there is an optimum D/d for the minimum settlement. However, the maximum lateral movement under the embankment toe is only slightly affected by D/d.