ABSTRACT
The Gongbei tunnel is one of the most technically challenging components of the Hong Kong-Zhuhai-Macau Bridge project. It was excavated using a pipe roof in combination with artificial ground freezing as pre-support. This paper presents the ground frost heave techniques during Gongbei tunnel excavation. Based on the thermal-mechanical coupling theorem, the development of the frost heave during ground freezing is simulated using COMSOL FE software. The effects of frost heave control using different techniques including pre-grouting, heating pipes to limit frozen ring thickness, and combination of the pre-grouting and heating pipes are analyzed and compared. The simulation results show that pre-grouting is critical to frost heave control by reducing the permeability of the soils and inhibiting the migration of moisture. The heating pipes are an effective supplement to frost heave control by limiting the thickness of frozen ring. The simulated ground surface heave is compared favorably with the filed measurement.
