吹填软土CU三轴剪切应力松弛特性试验研究

Experimental study on stress relaxation of soft dredger fill under CU triaxial shear

应力松弛与蠕变二者机制不同,不能简单复制。CU三轴剪切试验可以对许多工况进行模拟,而这些工况中可能包含了一定程度的应力松弛现象,由应力松弛导致的工程事故时有发生。天津滨海吹填软土具有显著的流变特性,以天津滨海吹填软土为研究对象,使用WF应力路径三轴仪,对土样进行固结不排水三轴剪切应力松弛试验。试验结果表明:应力松弛过程可分为快速、慢速和稳定3个阶段;一定范围内,应力松弛速率随初始松弛应变增大而增大;偏应力与时间对数之间存在近似线性关系;应力松弛对总抗剪强度指标几乎无影响,但使有效黏聚力c'减小,有效内摩擦角φ'增大。最后对试验数据进行了归一化和拟合,推导并验证了能够反映吹填软土应力松弛特性的应力-应变-时间关系模型。其研究结果对天津滨海吹填软土的流变性进行了补充,可为相关工程事故的防治提供理论参考。

Mechanism of Stress relaxation differs from creep in their mechanism, and they can not be simply exchanged. Consolidated undrained triaxial shear test（CU） can simulate many operating conditions containing a certain degree of stress relaxation. Engineering accidents caused by stress relaxation sometimes occur. Tianjin Binhai soft dredger fill has significant rheological properties. In this study, soft dredger fill was tested by triaxial-shear tests to examine the stress relaxation behavior of the soil samples under consolidated and undrained conditions. The results show that the stress relaxation process can be divided into rapid stage, slow stage and stable stage. Within a certain range, the stress relaxation rate increases with the increasing of initial deviator strain relaxation. there exists an approximate linear relationship between deviatoric stress and logarithmic time. Stress relaxation has little effect on the total shear strength index while decreases the effective cohesion c＇ and increases the effective angle of internal friction φ＇. Finally, a model for stress-strain-time relationship reflecting the stress relaxation characteristics of dredger soft fill is deduced and validated through fitting and normalizing the test data. This research has supplemented the rheological properties of Tianjin Binhai dredger soft fill, and can provide a theoretical reference for the prevention of related engineering accidents.