Abstract: The L-shaped diaphragm wall is broadly used to form an enclosed retaining structure underground. Due to the complicated stress condition during trenching construction, the stability of L-shaped trench is lower than that of regular rectangular trench. In this paper the instability mechanism of irregular-shaped diaphragm wall during the excavation of L-shaped slurry trench is revealed based on upper bound analysis. A 3D kinematically admissible mechanism defining the failure of the L-shaped trench is constructed. The safety factor of the trench and corresponding failure pattern are obtained through upper bound analysis. Moreover, the influences of trench geometries and soil properties on the trench stability are discussed through parameter analysis. The calculation result of a case study is consistent with the field ultrasonic inspection result.

Key words: L-shaped diaphragm wall, stability, trenching, upper bound analysis, safety factor