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Geomechanics and Engineering
  Volume 13, Number 5, November 2017 , pages 715-742
DOI: https://doi.org/10.12989/gae.2017.13.5.715
 


Numerical and experimental study of multi-bench retained excavations
Gang Zheng, Dongqing Nie, Yu Diao, Jie Liu and Xuesong Cheng

 
Abstract
    Earth berms are often left in place to support retaining walls or piles in order to eliminate horizontal struts in excavations of soft soil areas. However, if the excavation depth is relatively large, an earth berm-supported retaining system may not be applicable and could be replaced by a multi-bench retaining system. However, studies on multi-bench retaining systems are limited. The goal of this investigation is to study the deformation characteristics, internal forces and interaction mechanisms of the retaining structures in a multi-bench retaining system and the failure modes of this retaining system. Therefore, a series of model tests of a two-bench retaining system was designed and conducted, and corresponding finite difference simulations were developed to back-analyze the model tests and for further analysis. The tests and numerical results show that the distance between the two rows of retaining piles (bench width) and their embedded lengths can significantly influence the relative movement between the piles; this relative movement determines the horizontal stress distribution in the soil between the two rows of piles (i.e., the bench zone) and thus determines the bending moments in the retaining piles. As the bench width increases, the deformations and bending moments in the retaining piles decrease, while the excavation stability increases. If the second retaining piles are longer than a certain length, they will experience a larger bending moment than the first retaining piles and become the primary retaining structure. In addition, for varying bench widths, the slip surface formation differs, and the failure modes of two-bench retained excavations can be divided into three types: integrated failure, interactive failure and disconnected failure.
 
Key Words
    multi-bench retained excavation; model test; finite difference method; strain softening; failure mechanism; earth berm
 
Address
Gang Zheng, Dongqing Nie, Yu Diao, Jie Liu and Xuesong Cheng:
1)MOE Key Laboratory of Coast Civil Structure Safety, Tianjin University, 92 Weijin Rd., Nankai District, Tianjin 300072, China

2)Department of Civil Engineering, Tianjin University, 92 Weijin Rd., Nankai District, Tianjin 300072, China
 

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