In situ test and construction of two-shot grouting for waterproof of man-hole-pile

Pile underpinning of Baihuo Plaza with great underpinning force and complex construction environment is one of the important parts of Shenzhen Metro project. The new underpinning piles are manholepiles. Because of high permeability and high confined water head in substrata, the cutoff grouting is very important to construction of manholepile.In situ test demonstrates that twoshot grouting method with water glass as main material can increase strength and decrease permeability of soil. The soil treated by this method can resist 0.3 MPa hydraulic fracture pressure and satisfy form a cutoff for the 20 m long pile. The seepageprevention technology with twocomponent polymer can prevent ground from swelling. This technology has some merits,such as simple,convenient,small volume of machines and no waste liquid,and is applicable to the construction spot with small space. The practice demonstrates that the grouting constructed by the technology can prevent water very well when manholes are dug.