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Abstract When the soils around the foundation pit are actually in an unsaturated state，the design of anti-overturning retaining wall based on the saturated soil mechanics neglecting matric suction is unreasonable. Assuming the matric suction with the uniform and linear distributions，equations for critical embedment depths of anti-overturning were obtained on the basis of the unified solution of shear strength for unsaturated soils under the plane strain condition，and the moment equality considering the intermediate principal stress effect and the strength nonlinearity. The procedure of engineering application with the obtained results was given and the parametric analysis about the coefficient of critical embedment for anti-overturning was discussed. The proposed results are orderly solution series. The effect of strength theory on the anti-overturning design for rigid retaining wall of foundation pit led to remarkable difference. The greater strength of unsaturated soils in comparing to the saturated soil could be utilized considering the intermediate principal stress effect. The critical embedment coefficient was significantly influenced by the matric suction and its distributions. Therefore，the distributions of matric suction should be reasonably assumed and some engineering measures should be adopted to ensure its stability. Two methods can deal with the effect of strength nonlinearity of unsaturated soils：the method 1 with a small stable suction angle which is simple but conservative；while the method 2 with piecewise hyperbolic suction angle is precise but slightly complicated. The dual effects of high matric suction on the strength of unsaturated soil and the structural design should be correctly understood.
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Received: 04 January 2014
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2014, Vol. 33 
