高压缩性软土一维非线性大应变固结解析解

An analytical solution for one-dimensional nonlinear large-strain consolidation of soft clay with high compressibility

鉴于目前大应变固结解析解还不能充分考虑软土非线性压缩和渗透特性的现状,查阅大量室内固结渗透试验数据,验证固结过程中软土孔隙比与有效应力、孔隙比与渗透系数间的非线性关系在双对数坐标系中呈现非常好的线性特征,并给出双对数模型参数的变化范围。双对数压缩渗透模型不仅能有效地描述小应变下软土的非线性固结特性,其也能可靠地反映大应变下软土的非线性压缩渗透特性。基于此,引入双对数压缩渗透模型,在拉格朗日坐标系中以超静孔压为变量建立薄软土层的一维非线性大应变固结模型,并分别获得3种条件下模型的解析解。然后通过与室内试验结果和有限差分解对比,验证本文解析理论的可靠性。最后,对土层在不同应变条件下大、小应变固结理论间的固结性状差别展开讨论,表明当土体应变达15%左右时,分别利用大、小应变固结理论计算的超静孔压可达15%左右的差别,故当土层应变达到或超过15%时就有必要利用大应变固结理论开展土层的固结计算。

Aiming at the status that some one-dimensional large strain consolidation analytical solutions fail to fully consider the non-linear compression and permeability characteristics of soft soils,in this paper,data analysis of large numbers of laboratory compressibility and permeability tests was conducted, showing that there are good linear relationships between the void ratio with the effective stress and the permeability coefficient in the bi-logarithmic coordinate system,and the variation ranges of parameters for the bi-logarithmic model were also provided. The nonlinear compressibility and permeability model in the bi-logarithmic coordinate system can not only effectively describe the nonlinear consolidation characteristics of soft soils under the condition of small strain,but also reliably reflect the compression and permeability characteristics of soft soils under the condition of large strain. Based on the nonlinear compressibility and permeability model in the bi-logarithmic coordinate system,a one-dimensional nonlinear large-strain consolidation model for thin soft soil layer was developed in the Lagrangian coordinate system by considering the excess pore pressure as a variable. Besides,the analytical solutions for the nonlinear large-strain consolidation model under three conditions were derived,respectively. Then,the reliability of the analytical theory was verified by comparing with laboratory test results and finite difference solutions. Finally, the differences in consolidation behaviors between large and small strain consolidation theories under different strain conditions were discussed. It is found that,when the soil strain is about 15%,the deviation from the excess pore pressure between large and small strain consolidation theories can reach 15%,indicating that it’s rather necessary to use large strain consolidation theory to calculate consolidation when the corresponding soil strain reaches or larger than 15%.