Suggested method of utilizing soil arching for optimizing the design of strutted excavations

Abstract

An expression was derived for the soil arching effect behind foundation pits by considering the natural static equilibrium. An optimization strategy for super-large deep foundation pits was proposed based on the arching-related stress transformation and the limit span of soil arching. Steel–concrete composite piles that act as arching feet to formulate the soil arching are introduced. The proposed arching-effect methodology is supported using numerical modelling that reveals the stress arching in the principal stress contours. Once the interval between piles is less than the analyzed limit span of the soil arch, introducing steel–concrete composite piles can cause a sharp decline (by one third) in the wall deflection. It is essential that the steel struts are moved to the diaphragm wall where the steel–concrete composite piles form the arching feet and that the total number of steel supports remains unchanged. The formation of an arching foot can also significantly reduce the lateral wall deflection, enhancing the stability of the deep foundation pit during construction. Grouping the piles efficiently is a reliable tool for stabilizing deep foundation pits from the point of view of multi-arching action. Furthermore, the maximum principal stress contours reveal the arched trajectory between adjacent piles.