Innovative construction method for oversized excavations with bipartition walls

This paper presents an innovative construction method with bipartition walls (BPW), which was developed to reduce the excavation-induced adverse impact on the supporting structures and surrounding environment in oversized deep foundation pits. In the proposed construction method, apart from the retaining walls needed in the conventional foundation pits, two temporary parallel partition walls are constructed in the foundation pit to divide the oversized pit into two separated pits and a narrow pit in between. The separated pits can be excavated either successively or simultaneously, leaving the soil in the narrow pit to decrease the interaction of these separated pits. After the completion of the separated pits, the soil in the narrow pit is removed, and finally the temporary partition walls are demolished after the completion of the excavations. This proposed method that divides the oversized pit into small ones using BPW decreases the interaction between these pits and, thus, improves the excavation flexibility and decreases excavation deformations. To facilitate its application, numerical simulations are conducted to determine the spacing of the parallel partition walls. This innovative construction method was applied in an oversized foundation pit in Shanghai soft clay. Field investigation confirmed the applicability of the proposed construction method.