Study on temporary filling material of synchronous grouting in the middle of shield

The ground surface settlement is inevitable during shield tunneling, due to the over excavation by shield machine and the annular gap between the shield and surrounding soils (i.e., shield-out space). The shield-out space will become a part of the shield-end space during the shield tunneling, which requires that the filling materials is temporarily filled and cannot hinder the movement of the shield machine. In this paper, the clay shock was introduced, which is a two-component grouting material being promoted for the treatment of shield-out space. The viscosity of component A, mechanical strength, and microstructure of the clay shock were studied by a series of laboratory tests. The test results indicate that the final viscosity of component A is always in a range from 30 to 65 Pa.s. The viscosity of component A could be reduced by dispersant, while increased by stabilizer and thickener. The unconfined compressive strength (UCS) of the clay shock was weakened by dispersant, stabilizer, thickener, water and sodium silicate. The chemical reaction between sodium silicate and bentonite was more complete with the increment of water content, showing that the mass ratio of sodium silicate should be reduced for the high water content in practice. (C) 2020 Elsevier Ltd. All rights reserved.

Automated summary

Ground surface settlement is inevitable during shield tunneling due to over excavation by the shield machine and the annular gap between the shield and surrounding soils. Clay shock, a two-component grouting material, can be used to fill the shield-out space. Laboratory tests showed that the viscosity and mechanical strength of clay shock can be influenced by additives, and the chemical reaction between sodium silicate and bentonite is affected by water content.