非饱和土蠕变力学特性试验及分段模拟

水电工程中库岸边坡流变效应显著,以库岸边坡非饱和粉质黏土为例,描述其蠕变力学行为,开展基质吸力控制条件下的三轴压缩固结排水蠕变试验。试验表明:①非饱和粉质黏土在不同应力水平下蠕变曲线形态较为相似,在同一应力水平下,土样的瞬时应变都大于蠕变应变;②随着应力水平的提升,土样的瞬时应变和蠕变应变都呈递增趋势,且瞬时应变的增长幅度大于蠕变应变;③在不同基质吸力条件下,非饱和等时偏应力-应变关系均表现出较为明显的非线性特征。基于试验成果,分析粉质黏土蠕变变形特点,提出分段模拟的思路来描述瞬时应变和蠕变应变,分别构建考虑基质吸力的弹性体和分数阶黏滞体,由此建立可考虑基质吸力的非饱和粉质黏土蠕变本构模型。通过所建模型对本文和相关文献中非饱和粉质黏土蠕变数据进行辨识,对比分析试验曲线和预测曲线,证明所建模型的合理性和适用性。研究成果为库岸边坡长期稳定性研究提供一定参考。

Experimental and piecewise simulation of creepmechanical properties of unsaturated soils

In hydropower project, the rheological effect of reservoir bank slope is remarkable. Taking the saturated silty clay of reservoir bank slope as an example, the creep mechanical behavior of reservoir bank slope is described, and the creep test of triaxial compression consolidation drainage under the condition of matrix suction control is carried out. The results show that :(1) the creep curves of the unsaturated silty clay are similar in different stress levels, and at the same stress level, the instantaneous strain of the soil sample is greater than the creep strain; (2) with the increase of the stress level, the instantaneous strain and the creep strain of the soil sample are increasing; (3) under different substrate suction conditions, the partial stress-strain relation of the unsaturated and the like shows a more obvious non-linear characteristic. Based on the results of this paper, the idea of subsection simulation is put forward, and the elastic body and the fractional-order viscous body which take into account the suction of the matrix are respectively constructed, and the creep constitutive model of the unsaturated silty clay is established. The model is used to identify the creep data of unsaturated silty clay in this paper and the related documents, and the experimental curve and the prediction curve are compared. The rationality and applicability of the model are proved. The research results provide some reference for the study of long-term stability of reservoir bank slope.