Method for calculating anti-capsizing critical built-in coefficient of unsaturated soil foundation pit retaining wall and application thereof

The invention discloses a method for calculating the anti-capsizing critical built-in coefficient of an unsaturated soil foundation pit retaining wall and the application thereof. The method comprises the following steps that the plane strain shear strength unified solution with the nonlinear strength of unsaturated soil under high matrix suction is calculated; the active and passive soil pressure intensity of the unsaturated soil is calculated; the capsizing torque and the anti-capsizing torque of the anti-capsizing stability of the foundation pit retaining wall are calculated; when the matrix suction is not changed or in linear change along the depth, the cubic equation of an anti-capsizing critical built-in depth D1 is calculated, and therefore the anti-capsizing critical built-in coefficient of the unsaturated soil foundation pit retaining wall is obtained. According to the method, based on the plane strain shear strength unified solution of the unsaturated soil, the middle main stress effect and the nonlinearity of the strength of the unsaturated soil are considered, the anti-capsizing critical built-in depth equation of the foundation pit rigid retaining wall under two kinds of matrix suction distribution is derived, engineering application steps are given out, parameter influence characteristic analysis is conducted on anti-capsizing critical built-in coefficients which are newly provided, and a certain theoretical foundation is provided for reasonable design and construction of an unsaturated soil foundation pit supporting structure.