Experimental Study On Effect Of Oval Rotation Of Principal Stress Orientation On Saturated Sand

Wave loading is a very important basic loading in the ocean construction,development and utilization. Wave loading loads on the seabed soil directly and causes dynamic stress, dynamic strain, dynamic pore water pressure. When the pore water pressure increases to the consolidation pressure, the effective stress will be close to zero of the soil, which reduces soil strength and even lead to large strain and instability failure, the consequences could be disastrous. So the damage form part of the project has been confirmed instances. Cyclical changes in ocean surface waves on the sea bed surface reciprocating wave pressure wave under the influence of this cycle pressure variation of normal stress and shear stress and the total deviation combination of stress are changes in the cycle, Turkey seabed principal stress axis rotation body occurs continuously.Existing test results show that the continuous rotation of principal stress axes will be significantly reduced so that sand liquefaction strength. In the existing principal stress rotation tests, mostly circular stress path, but for the more general case of elliptical stress path tests, is less relevant research data. Therefore, it is necessary that the mechanical behavior of soils under complex stress conditions tested explore. In this paper, the use of advanced "soil static-dynamic triaxial - torsional shear apparatus" , for 40% the density of saturated loose sand and 70% the density of saturated dense sand carried out considering the direction of rotation of principal stress changes in a series of elliptical shaped stress path tests, holding a load component remains unchanged, change to another load weight and change the phase difference angle, focused on the impact of the load component and phase angle of the dynamic behavior of sand. The main contents and results are as follows:1. First, for dense sand a series of fixed load weight gradually change the amplitude of the amplitude of the other load components elliptical stress path tests, focusing on under different stress conditions oval saturated dense sand deformation and strength properties. The results show that:the widely used expression shear stress cycle dynamic strength analysis can not accurately reflect the dynamic strength oval principal stress rotation stress paths, and proposed a new expression for the dynamic stress analysis of complex stress paths dynamic strength properties.2. Design special comparative tests of loose sand also as dense sand similar test, and change the confining pressure, whether dynamic stress more precise expression can be analyzed to verify the proposed dynamic strength characteristics of complex stress path. The results show that the stress in the elliptical path test, while maintaining the vertical deviation stress or shear stress of a component to another component of constant change, like the dynamic strength of saturated sand will change a larger range. Confining pressure effect on the dynamic strength of sand is also more significant. When the confining pressure is large, changing the vertical deviation stress or shear stress, dynamic strength vary widely, but at low confining pressures, this difference was not significant.3. Finally, change the phase angle of the size of loose sand similar to the above experiment, focused on the phase angle of the impact of sand characteristics. Experimental results show that:with the change of phase angle, sand failure to achieve the required vibration times is not the same. When the phase angle is gradually reduced to 90°0°, sand strength increases.