The Simplified Formula For Calculating The Permanent Strain Potential Of Soft Soil And Parameter Analysis

The permanent strain potential of soil is defined as the permanent strain of the soil where the dynamic stress is returned to zero after the dynamic stress is cycled once.The permanent strain potential directly reflects plastic deformation capacity of soil under dynamic loading,which is closely related to the seismic subsidence of soil.The permanent strain potential of soil can be accepted through dynamic triaxial test,and it can also be accepted by the empirical formula.Soil property,the cycle number of dynamic stress,dynamic stress and confining pressure in the empirical formula are defined as dynamic parameter.The permanent strain potential is related to the dynamic parameters of soil.In the thesis,the permanent strain potential formula is studied by calculating several working conditions.The unreasonable parameters of the formula for calculating the permanent strain potential are modified,and also the validity of modified settlement parameters is tested.Meanwhile the importance of each dynamic parameter on the permanent strain potential is calculated on this basis.The classification criteria of permanent strain potential is put forward by analyzing the curve of permanent strain potential,which is consisted by some control parameters.The main work completed includes the following:1.The unreasonable parameters of the formula for calculating the permanent strain potential are pointed out in this paper.According to the curves of shear wave velocity versus settlement parameters,the unreasonable parameters of the formula for calculating the permanent strain potential are modified through considering the derivation process of the permanent strain potential formula.2.The qualitative analysis of the modified settlement parameters have been accomplished.Based on the modified settlement parameters,the program is applied to simulate the seismic settlement in Tangshan earthquake to test the correctness of the modified settlement parameters.Actual settlement in Tanggu area of Tangshan earthquake is consistent with the simulation results.To test examine the correctness of the permanent strain potential formula,the permanent strain data in the dynamic triaxial test is compared with the permanent strain potential under the same conditions.3.Modified settlement parameters are conducted to study the influence law of permanent strain potential by soil and dynamic parameter.Using the CART method,the importance of dynamic parameters(soil property,the cycle number of dynamic stress,dynamic stress and confining pressure)is acquired.Sensitivity analysis method is utilized to calculate sensitivity of dynamic parameters(soil property,the cycle number of dynamic stress,dynamic stress and confining pressure).4.Level of permanent strain potential is defined through observing the seismic settlement of several working conditions.The classification criteria of permanent strain potential is prescribed by considering the curves of permanent strain potential.Using CART method,the Classification and Regression Tree is established.Based on the Classification and Regression Tree,the estimation of permanent strain potential is put forward,which is consisted by some control parameters.