The Twin Shear And Triple Shear Unified Solution Of Earth Pressure For Unsaturated Soil Retaining Wall

Along with the development of social economy, the exploitation and utilization of underground space has become an important and urgent issue. In the construction of underground construction and engineering facilities, it is inevitable to encounter the problem of unsaturated soil. These unsaturated soils are closely related to geotechnical engineering problems, and the earth pressure is one of the basic problems in geotechnical engineering. The influence of different strength criterion on the calculation result of earth pressure is very obvious. Therefore, it is very important to study the problem of retaining wall earth pressure of unsaturated soil by choosing appropriate strength criterion.Based on the twin shear unified strength theory and triple shear unified strength criterion, taking the unsaturated soil as the research object, combining with the existing unsaturated soil anti shear strength formula, the derivation is carried out by using the classical Rankine earth pressure theory and the Coulomb earth pressure theory. Active earth pressure and passive earth pressure for unsaturated soil are studied by considering the strength criterion difference, intermediate principal stress effect, matrix suction, effective friction angle, matrix suction angle factor influence, etc. The main research contents and conclusions include:Combining the twin shear unified strength theory and the unified solution of shear strength for unsaturated soils in terms of two state stress variables, Unified solution of Coulomb"s active and passive earth pressureunified solution is obtained by the method of static balance method of sliding wedge. The results considering the effect of the intermediate principal stress, matrix suction influence factors, contains a series of existing saturated soil and unsaturated soil pressure calculation formula, and the results is more in line with the actual situation of unsaturated soil pressure calculation method.The existing classical Rankine earth pressure formula was improved based on triple shear unified strength criterion. According to the stress limit equilibrium theory, combined with the triple shear unified solution of shear strength for unsaturated soil, triple shear Rankine earth pressure unified solution is derived based on the triple shear unified strength criterion for unsaturated soil. The results can be used to explore the active earth pressure and passive earth pressure problems for unsaturated soil when the back of vertical retaining wall is smooth and filling soil is level. The double slip angles of the twin shear unified yield criterion are also overcome.Based on the triple shear unified strength criterion, considering the influence of the intermediate principal stress effect and the matrix suction, the triple shear Coulomb earth pressure unified solution for unsaturated soil is derived. In addition to the influencing factors mentioned above, the unified solution can also consider the influence of the wall back inclination angle, the inclination angle of the fill, the external friction angle and cohesion, etc. The influence of different parameters on the triple shear Coulomb earth pressure unified solution for unsaturated soil is also explored.