变荷载下不排水桩复合地基桩间土和下卧层土固结分析

Consolidation analysis of surrounding and underlying soils in a composite ground with impervious pile under variable loading

基于悬浮不排水桩复合地基超静孔隙水压力解答,建立了变荷载条件下复合地基桩间土和下卧层土平均固结度的解析解。通过与有限元解答的对比,证明了解析解的正确性和有效性。利用解析解对桩间土和下卧层土的固结性状进行了分析。研究发现,桩间土的固结速率远大于下卧层土,并随置换率和桩土模量比的增加而增大。在工程设计采用的置换率范围内,桩的贯入比较小时,下卧层土的固结速率受置换率和桩土模量比的影响很小;桩的贯入比较大时,下卧层土的固结速率随置换率和桩土模量比的增加而增大。桩间土和下卧层土的固结存在临界置换率和临界桩土模量比,超过临界值后,桩间土和下卧层土的固结速率不随桩土模量比和置换率的增加而增大。桩间土和下卧层土的固结速率随加荷速率的增加而增大。

By the analytical solution of the average excess pore water pressures in a composite ground with a floating impervious pile, an analytical solution is obtained for the consolidation of surrounding and underlying soils under variable loading. The validity of the proposed solution is illustrated by comparing the present solutions to the FEM results. The consolidation behavior of the surrounding and underlying soils is investigated using the current solutions. The results indicate that the consolidation rate of the surrounding soil is considerably larger than that of the underlying soil, and it increases with the increase of area replacement ratio and constrained modulus ratio of a pile to surrounding soil. The consolidation rate of the underlying soil is hardly influenced by the constrained modulus ratio and area replacement ratio when the area replacement ratio is located within the range recommended in engineering design, and penetration ratio of a pile is not large enough. The consolidation rate increases with the increase of the constrained modulus and area replacement ratios. There exist some critical values of the constrained modulus ratio and area replacement ratio, beyond which consolidation rates of the surrounding and underlying soils are insensitive to the variations of these two parameters. The consolidation rates of the surrounding and the underlying soils always increase with the increase of loading rate.