Analytical solutions for stability of slurry trench

Coulomb-type force equilibrium analyses are presented for general two- and three-dimensional stability of a slurry-supported trench. Analytical solutions are derived for the factor of safety and critical failure plane angle in each case for drained effective stress and undrained total stress conditions. The solutions can accommodate variable trench depth, trench length, slurry depth, groundwater table elevation, surcharge loading, tension crack depth, and level of fluid in the tension cracks. Drained analyses can account for c' - phi' soil strength and the effect of soil suctions above the groundwater table using the total cohesion method. Undrained analyses can account for undrained shear strength that varies linearly with depth. The solutions reduce to previously published expressions for simplified cases. An example problem is provided to illustrate variations of the factor of safety and critical failure plane angle with the length of a three-dimensional slurry trench. Finally, the method shows excellent agreement with the results of a full-scale field experiment of the failure of a diaphragm wall slurry trench constructed in silty sand.