Study on Induced Anisotropy of Sand by Particle Flow Code
|School||Zhejiang University of Technology|
|Keywords||sand consolidation way cyclic load particle flow code microscopicfabric induced anisotropy|
The practice projects like excavation, embankment dam and water storage stage,the stress state changes are causing the soil to produce the classic examples of inducedanisotropy, but previous studies have attributed more to the stress path impact on soilstress–strain, and there is no clear from the view of anisotropy. Solve practicalengineering problems, the need for further research induced anisotropy. In this paper,the PFC2D (2dimensional particle flow code) is applied to research on this problem.The research works are as below:1. Study on the evolution law of induced anisotropy of sand at different consolidated stresslevel and consolidated stress ratio, and its effect on the deformation under monotonicloading. Through the quantitative description of the evolution of microscopic fabricparameters of the induced anisotropy, to be clarified the macroscopic mechanicalproperties and micro-mechanism. And the size effect on the impact of the inducedanisotropy of samples.2. Study on the induced anisotropy of sand under cyclic shear, including: tomaintain the same stress level, cyclic deviator stress amplitude were at Δt=5%,10%,20%p, test on cyclic shear of soil samples; to maintain the amplitude of cyclic deviatorstress Δ q=10%p constant, test on the sand under different stress levels.Summarized the following conclusions:1. In the numerical simulation, large enough confining pressure could eliminate theinherent anisotropy of the sample, which produced by sample preparation or deposited. The sample under anisotropic confining pressure showing the significantly initialanisotropy, and the principal anisotropic direction are parallel with the main direction ofmaximum principal stress in consolidation stress.2. In the later stage of monotonic loading,60%of induced anisotropy is caused bythe normal contact force anisotropy, and the principle direction could fully represent thedevelopment of normal contact force. Therefore, in the fabric parameters, the contactnormal force anisotropy can best represent the degree of development of inducedanisotropy.3. In the numerical simulation of size effect, the number of particles contained inthe sample could greater effect on stress and induced anisotropy of the peak, thecoordination number. But changes in the shape of the specimen could not affect the testcharacteristics of the macro and micro mechanics.4. Cyclic shear stress amplitude control the development of induced anisotropy,stress level will not affect the induced anisotropy changes.