Analytical procedure for massive water-sealing barriers used in deep excavations considering seepage effect and its application

Abstract

This paper presents an analytical procedure for massive water-sealing barriers (MWSBs) that are made of partially overlapped jet-grouting columns used for deep excavations, in which two crucial factors of the permeability and strength of jet-grouted materials are considered. Subsequently, a calculation example is analyzed and discussed. Results show that “tension failure” mechanism is a major concern for the structural failure during a design of MWSBs. The maximum allowable seepage discharge is a crucial index for the design of MWSBs, which has a significant influence on determining the design parameters of MWSBs. Compared with the design procedure for MWSBs that is proposed in this paper, the design parameters of MWSBs determined by the stability equilibrium and seepage stability equilibrium approaches are conservative due to the fact that it fails to consider the permeability or strength of jet-grouted materials that makes a contribution to the structural safety. Based on the proposed design method, the ranges of both the thickness and depth of MWSBs for a case history of subway excavation in Fuzhou, China were determined. Finally, field pumping test results showed that the water-tightness performance of MWSBs performed at site was quite well.

Keywords

rectangular excavations / deep aquifers / massive water-sealing barriers / seepage / design procedure

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