Upper bound analysis of tunnel face stability in layered soils
The working face of tunnel constructions has to be kept stable during tunneling to prevent large soil deformations or fatal failure. In layered soils with lower cohesion, failures happen more often and more abrupt than in cohesive soils. Therefore, the maintenance of a proper support pressure at the tunnel working face is of high importance. In this paper, an upper bound analysis is introduced to investigate the minimum support pressure for the face stability in layered soils. A three-dimensional kinematically admissible mechanism for the upper bound analysis is improved to model potential failure within different soil layers. An analytical solution for the support pressure assessment is achieved. The influence of the crossing and cover soil on the face stability is analyzed, respectively. This solution provides an analytical estimation of the minimum support pressure for the face stability. It may be used as a reference for projects under similar conditions.
KeywordsFace stability Layered soil Support pressure Upper bound analysis
The authors appreciate the constructive advices of Prof. Dr.-Ing. H. Balthaus to this paper. The research is supported by the Funding of the National Natural Science Foundation of China (Grant 51179168) and the Major Projects on Science and Technology of Development of Society of Zhejiang, China (Grant 2009C030081).
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