In the paper,the water-proof curtains of cantilever cast-in place piles and jet-grouted piles are designed and calculated,therefore,some useful results are obtained for further design of foundation pit protecting and construction.

Based on the engineering case,this paper presents,in the complicated surroundings and under the geological conditions of strong water permeability,the construction technique for pit waterproof curtain by the method of high-pressure jet grouting with triple tubes.

Such new technologies as hydraulic prop sustaining and fast filling method with curtain separation were adopted so as to enable the synchronous sealing of mined out area and the mining operation, and mining efficiency was increased substantiall