Tunneling slurry purification of shield-driven tunneling engineering in the Second West-to-East Gas Pipeline

According to the problem that the shield machine, used in the Beijiang shield-driven tunneling engineering of the second West-to-East Gas Pipeline, produced a great amount of waste slurry during the tunneling process in the silt-like clay layer, and thus caused a low slag discharge efficiency of slurry circulation system of the shield machine, high energy consumption of high-speed cyclone device, which was not conducive to environmental protection, etc., the authors studied to add a mud processing system to the slurry circulating system of the shield machine to solve the problem of decreased efficiency of high-speed cyclone device (Scheme 1: bentonite+CMC+soda ash+water, Scheme 2: bentonite+clay+CMC+soda ash+water), and finally confirmed that Scheme 2 was more suitable for local formation conditions. The field applications and testing and evaluation results of local environmental protection department showed that adding a mud filter press processing system can improve the purification efficiency of the shield machine's mud circulating system for silt-like clay, meeting the environmental requirements of direct discharge after the liquids treatment, and the slurry circulation system had an increased energy saving effect compared to the non-improved slurry circulating system, with sound social and economic benefits.