The Catastrophe Theory Subjected To Damage Of Soil Body Under Dynamic Load

A large variety of experiments about saturated loose sand under complex stress conditions were done in this thesis. Then comprehensive and systematic analysis on deformation and strength characteristics of saturated loose sand, which is under the monotonous and cyclic shear load, was done. By using mutation theory, a constitutive mode of saturated loose sand was build, and sharp point mutation model was used to simulate the development process of its shear failure. Through the judge of the test data, it is believed that this method can be used to determine the damage of saturated loose sand.The experiment was mainly done through cyclic shearing, and the key point is the simulation of damage process of saturated loose sand under earthquake condition. When doing the experiment, against stress - contingency mode of development and the development of the pore water pressure, the impact of the principal stress on the initial direction was discussed. Tests showed that the impact of initial principal stress direction angle on the stress contingency mode is very significant. Under non-equal conditions, when the consolidation at the level of stress-shear stress that is 0°and 90°, the principal deformation is mainly in axial direction which is caused by straight stress deviation. On the contrary, in non-equal conditions, when the angle between straight stress direction and the vertical is 30°, 45°and60°, the cumulative effect of the cycle effect is very significant. And this law appears to be that there is no necessarily link with the principal stress factor. Thus the initial shear stress that the role can not be ignored. Consolidation in equal conditions, the consolidation of the sample did not shear stress the role of pre-cut, at this time shear strain of the cycle and the cumulative effects are very significant, and the cumulative effect of this is symmetrical, not a one-way. As the consolidation under the conditions of equal strength with the cycle of vibration, the increase gradually decreased, resulting in a cumulative sample of the residual deformation developed faster.Some analysis done for the initial 25 states of saturated sand with the pore water pressure and the development process of generalized shear strain. The results showed that the conditions with three non-equal to consolidation stress, the pore water pressure has always been less than the initial consolidation of an effective mean stress, is not in accordance with the usual definition of the initial liquefied (that is, pore pressure to achieve the initial consolidation of effective stress) as the destruction of standards. Found in practice, the process of vibration, even if the pore water pressure did not achieve an effective and stable average consolidation pressure in the vicinity of a certain level, the deformation of the development will remain very quickly. This deformation includs the axial deformation and shear deformation at the same time, so choose the generalized shear strain to 5 percent to the standard of destruction.In the past, the soil constitutive model built by mutation theory mainly used pore pressure as the state variables to judge the liquefaction of the soil. Based on the experiment, this paper introduced broad shear strain into the model as a state variable, making up the inadequate of pore pressure as a judgment. According to test data and characteristics of sand, the physical boundary conditions were established, and model of the relevant parameters are determined to improve the constitutive model formula. Based on test data, the vibration can factor coefficient was amended, an increase of the constitutive model flexibility and accuracy. Finally, on the back-test data, we can see that this model has high accuracy. So that will be applied to the mutation theory of complex saturated sand under the stress of the damage is feasible.