Deformation Characteristics of Bored Pile for Super-Large Circular Bermed excavation

Rectangular and/or irregular polygonal excavation can easily cause the detrimental corner effect, whilst circular excavation has the obvious beneficial spatial arching effect, being suitable for use as a normal excavation scheme for super-large foundation pit. In this paper, a simplified calculation method for bermed excavation is derived to analyze the deformation characteristics of bored pile for super-large circular foundation pit in thick soft soil regions. The results obtained from numerical analyses and field measurements are used to evaluate the effectiveness of the proposed theoretical approach for bermed excavation. It is found that the reduction coefficient of earth pressure α has a continuous profile with depth within the range of earth berm and supporting structure, and it is a function of depth z only. The simplified theory is practical and operable by comparing with the results of conventional finite layer method, and the theoretical results are consistent with the field measured data. In addition, for bermed excavation, a balanced layout of earth berms in a symmetrical manner is more beneficial to control the deformation of foundation pit. Essentially, the simplified theory can enhance the application of bermed excavation in foundation pit engineering, and improve the excavation efficiency.