Abstract:

Salt invasion causes substantial filter loss, viscosity and dynamicplastic ratio reduction of the lubricating slurry used for pipe jacking, and increases the pipe friction resistance affecting the pipe jacking construction. Hence, a case study is conducted on the geological survey results of the 2nd phase of the Yellow rivertoEast China water diversion project in the Shandong province. Saltresistant materials, such as attapulgite and HV-CMC are selected, and a slurry formula of water +5% attapulgite +5% bentonite +0.35% NaOH + 0.8% HV-CMC is obtained using a slurry test. Salt resistance and permeability experiments are conducted to test the viscosity, filter loss, and impermeability indexes before and after salt invasion. The following is concluded based on the results: (1) Owing to the high valency and poor hydration capacity, calcium and magnesium ions have a greater influence on salt invasion than sodium ions. (2) The viscosity of the lubricating slurry first rapidly decreases and then tends to be stable with an increase in salt intrusion. (3) The formation particle size has a great influence on the impermeability of slurry. The results suggest that the impermeability of undisturbed soil should be tested before slurry application.

Key words: pipe jacking, lubricating slurry, salt resistance slurry, salt invasion mechanism, salt resistance experiment