Effect of Nano-CaCO_3 on the Sealing Efficiency of Grouts in Flowing Water Grouting

摘要

Flowing water grouting is a big challenge in the tunneling and underground engineering. To enhance the early strength and grouting effectiveness of slurry for flowing water grouting, nano-CaCO_3 and fly ash were mixed with cement based grout. A series of physical simulation tests were conducted to simulate the flowing water grouting process in rough rock fracture, and investigate the effect of nano-CaCO_3 content on the fluid pressure and sealing efficiency of grouts. Results of viscosity tests show that the viscosity of grouts decreased with an increase of nano-CaCO_3 content. Scanning electron microscope (SEM) tests indicate that nano-CaCO_3 can promote the formation of fibrous hydrates and enhance the flowing water resistance of grouts. Increasing nano-CaCO_3 content resulted in the first increase while later decrease of maximal fluid pressure (MFP) and sealing efficiency (SE) of grouts. Reducing water cement ratio of grouts and incorporating fly ash can effectively improve the SE of flowing water grouting.