Experimental Investigation of Flow Control Technology for Grouting and Blocking of Flowing Water in Karst Conduits

Aiming at the grouting treatment in karst conduits with large flow and high velocity, we developed a simulation experiment system for conduit-type grouting blocking and investigated the blocking mechanism of flowing water grouting under the condition of flow control. Firstly, we studied the effect of flow control in conduit by controlling the opening of outlet valve and analyzed the variation law of velocity and pressure in conduits under different water heads, conduit diameters and valve opening quantitatively. Secondly, we conducted experiments of flowing water grouting under different flow control conditions, and revealed the influence law of flow control for flowing water grouting. The results show that: 1) with the increase of the intensity of flow control, the pressure in conduit increased gradually, and the velocity of flowing water decreased gradually. 2) When the volume ratio of water and cement was 1.2:1, the volume ratio of cement and sodium silicate was 2:1, the grouting volume was 540 L/h, and the flowing water velocity was 0.15 m/s, flowing water blocking under the condition of flow control achieved the optimal effect. 3) With flow control, the slurry deposition thickness increased more than 50% compared with no flow control; besides, the slurry retention rate increased, and the blocking effect significantly improved. The technology has been successfully applied in the grouting treatment project of China Resources Cement (Pingnan) Limestone Mine. And main water inflow points in the mine were blocked with an total amount of similar to 210,200 m(3)/d water reduction. This study provided some theoretical guidance and reference experience for treatment engineering of water inflow in karst area.