Research On Deformation Characteristics Of Sands Under Continuous Rotation Of Principal Stress Axes

As everyone knows, sand is a kind of common ground. As the foundation of a large number of buildings and structures, it has been subjected to various complex dynamic loads of a long time. Earthquake, wave and traffic load is the most representative. The continuous rotation of the principal stress axis is the main characteristic of the foundation soil under various complex dynamic loads. Meanwhile, a large number of research results show that the capacity of sand liquefaction resistance is obviously reduced under the condition of continuous rotation of the principal stress axis. But, the research results of stress path condition of deformation characteristics and characteristics of non coaxial soil in a variety of complex stress is less at home and abroad. This lack of awareness will not only cause huge economic losses to society, but also a threat to human life and safety. Therefore, it is very necessary to study the deformation characteristics of sand under complex stress path.In this paper, the dynamic characteristics of sand under complex stress paths are studied by using the hollow cylinder torsional shear apparatus. The main research work and research results are as follows:(1) According to the complex stress path of soil in nature, which is difficult to simulate in the laboratory. In this paper, the capability of simulating the complex stress path of the hollow cylinder torsional shear apparatus is studied. First of all, derive the mathematical equation of complex theory load loading waveform under the condition of stress path and the stress components increase waveform. Then, the theoretical waveforms are compared with the actual waveforms in the test process. By comparison, the hollow cylinder torsional shear apparatus can simulate the complex stress path in this paper.(2) According to the deformation characteristics of sand under the stress path of the principal stress axis. In this paper, the experiment of six sets of saturated sand under the stress path is carried out by using the hollow cylinder torsional shear apparatus to study the deformation characteristics of sand under the stress path. In the test set different intermediate principal stress coefficient b value and different deviatoric load Q value respectively on two sets of coefficients of sand deformation characteristics and the effect of the non coaxial behavior. The research shows that Sand showed obvious deformation characteristics and non coaxial behavior under pure rotation of principal stress axes. The deformation characteristics of sand and non coaxial characteristics by the influence of intermediate principal stress coefficient B is obvious.(3) According to deformation characteristics of sand under the direction of the principal stress direction and the stress path under synchronous stress. In this paper, the experiment of four sets of saturated sand under the stress path is carried out by using the hollow cylinder torsional shear apparatus to study the deformation characteristics of sand under the stress path. Through the test of saturated sand in the further study of more complex stress paths are showing more complex deformation characteristics. In different test schemes, the different values of the principal stress coefficient b, the initial partial stress and the variation of the partial stress are set up. To study the influence of these three factors on the deformation characteristics of sand.