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为了经济、有效地处理双层软弱地基,提出了变截面搅拌桩加固方法,在高压缩性土层中采用较大的桩体置换率,在中等压缩性土层中采用较小的桩体置换率,从而形成桩体置换率随土层性质变化的变截面搅拌桩复合地基。通过三维数值模拟对双层软弱地基中的变截面搅拌桩复合地基承载特性进行了研究。不同设计参数的变截面搅拌桩复合地基桩间距相同、桩长相同、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)不同。数值模拟结果表明:双层软弱地基中变截面搅拌桩复合地基的极限承载力显著高于等截面搅拌桩复合地基,最高达后者的1.8倍。变截面搅拌桩复合地基极限承载力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极限承载力最大。
In order to deal with double-layer and weak foundation economically and effectively, a method of reinforcement with variable section mixing piles is proposed, which uses a larger displacement ratio of piles in high compressibility soil layers and a smaller replacement of piles in medium compressibility soil layers Rate, so as to form a composite foundation with variable cross-section mixing pile with the change of pile replacement rate with soil properties. The bearing capacity of composite foundation with variable section mixing piles in double-layered soft ground was studied by three-dimensional numerical simulation. Different design parameters of the variable section mixing pile composite foundation pile spacing the same, the same pile length, the equivalent area replacement rate (volumetric replacement rate) the same, but the size of the pile diameter ratio (enlarged head diameter / small pile diameter) different. Numerical simulation results show that the ultimate bearing capacity of the composite foundation with the variable cross-section mixing pile in the double-layered weak foundation is significantly higher than that of the composite foundation with the mixing cross-section mixing pile, up to 1.8 times. The ultimate bearing capacity of composite foundation is closely related to the ratio of pile diameter to pile diameter, and the optimal pile diameter ratio results in the maximum ultimate bearing capacity of composite foundation.