应力主轴连续旋转对冻结黏土变形特性的影响

Influence of continuous rotation of principal stress direction on the deformation characteristics of frozen clay

摘要:

冻土的变形特性是寒区基础设计中地基变形稳定性验算的重要参数,且随应力方向改变而发生变化,现有研究中鲜有考虑应力主轴方向变化对冻土变形特性的影响。为此,采用冻土空心圆柱仪,对冻结黏土开展一系列纯应力主轴单向旋转试验,探索应力主轴方向角α旋转速度及旋转方向对冻结黏土变形特性的影响规律。结果表明:纯应力主轴旋转中,即使不改变应力幅值,也会在冻结黏土中产生塑性变形,变形过程中应变峰值滞后于应力峰值；α旋转速度会对单向旋转中冻结黏土的轴向应变及剪应变产生较大影响,存在一临界α旋转速度,在该条件下,冻结黏土能较好发挥其承载能力；α旋转方向不同改变了冻结黏土的受力过程,且冻结黏土中形变量越大,α旋转方向对其变形的发展规律影响越明显。滞回曲线特性分析表明,当α旋转速度较小时,会对冻结黏土的强度有较大影响,当α旋转速度较大时,对冻结黏土强度的影响反而会降低。α旋转方向对冻土强度的影响与所受的应力路径参数选取密切相关。

Abstract:

The deformation characteristics of frozen soil are important parameters for testing the stability of foundation deformation in foundation design of cold region, changing with the change of stress direction. However, the influence of principal stress axes direction on the deformation characteristics of frozen soil is rarely considered in existing studies. This paper carries out a series of principal stress unidirectional rotation tests on frozen clay by using frozen soil hollow cylinder apparatus. The influence of rotation rate and rotation direction of principal stress angle α on deformation characteristics of frozen clay is explored. It is found that plastic deformation can be generated in the frozen clay without changing the stress amplitude in pure principal stress axes direction rotation tests. The strain peak of frozen clay lags behind the stress peak in the deformation process. The α-angle rotation rate can affect the axial strain and shear strain of frozen clay, and there is a critical α-angle rotation rate to make the frozen clay play better carrying capacity. Different α-angle rotation direction changes the stress process of frozen clay, and the larger the shape variable of frozen clay, the more obvious the influence of α-angle rotation direction on its deformation development. Through the analysis of the hysteresis curve, it is found that α-angle rotation rate will have a greater impact on the strength of the frozen clay when the α-angle rotation rate is small. Nevertheless, its impact on the strength of frozen clay will be reduced when the α-angle rotation rate is large. The influence of α-angle rotation direction on the strength of frozen clay is closely related to the selection of stress path parameters.