A Novel Stability Analysis Method of Diaphragm Wall Trench and Its Application

Understanding stability of the trench of diaphragm wall is a basis for ensuring the safety and quality of trenching construction. Conventional stability evaluation model is based on Rankine earth pressure theory, which calculated value is conservative. Hence, this work focus on developing a new model for diaphragm wall trench based on Coulomb earth pressure theory. In order to analyze its overall failure mechanism and condition, the overall failure sliding block model of the trench was firstly established. Based on the Coulomb failure theory, the minimum mud weight and safety factor of the trench in limit equilibrium state was obtained. The parameter sensitivity of the proposed method and mechanical equilibrium method was compared and analyzed. Finally, two mud weight calculation methods were compared and verified with an engineering example, namely Shapingba deep foundation pit project, China. The results show that compared with the previous methods, this method fully considers the cohesion on the vertical side of the sliding body, and the value of safety factor is relatively large, which is more suitable for the stability analysis of clay and sand trench, and safety factor is mainly affected by the length of the trench, the friction angle of soil, mud weight and the relative height difference between the mud and water level. The actual mud weight is within the control range of theoretical calculation, and the theoretical analysis is verified by field ultrasonic testing. Hence, this method can be used to analyze stability of diaphragm wall.