A minimally invasive method for reinforcing the karez tunnel in Turpan based on the high mole ratio potassium silicate

摘要

The karez, a historical water conservancy heritage, still plays an irreplaceable role in irrigation and oasis ecology in Turpan. However, more spalling and collapse problems occur in karez tunnels which required to be reinforced. Field surveys in Ahong karez of Turpan prove that the water of sidewall mainly comes from continuous migration from the culvert and water vapor adsorption in winter. Three typical stages were classified from the damage morphology of tunnel, i.e., exfoliation of sidewall, crack, and collapse of vault, which are linked with capillary action and strength deterioration of loess after freeze-thaw. The high mole ratio potassium silicate (HMPS) with three mass percentages (0%, 3%, and 5%) was used in reinforcing the loess. By comparing the frost heave ratio, strength parameters, capillary rise height, water retention capacity, and microstructure, 3% HMPS is a favorable option to improve the engineering performance of sidewall loess after freeze-thaw. A minimally invasive method for reinforcing the karez tunnel was proposed based on borehole grouting and anti-seepage along the culvert. The unsaturated seepage analysis was carried out to determine the rational range of anti-seepage section. An optimal reinforcement length of 11.4 m is suggested for Ahong karez.