Well wall water leakage control technology of vertical well drilling method in coal mines based on grouting of ground directional drilling

The coal mine drilling shaft wall is a single-layer structure, and water leakage in the deep alluvium will seriously threaten mine safety. If there are construction defects in the stubble part of the well wall at the construction stage, it will lead to groundwater corrosion and rust through the metal and the weld seam of the stubble part, resulting in water leakage from well wall, which, if not treated promptly, is prone to lead to a sudden water-sand inrush and flooding accidents. In order to explore an effective treatment technology, a research on the control technology of water leakage from the wall of coal mine drilling wells was carried out with the background of water leakage control of wall of sub-well of the Xutong Coal Mine. Firstly, the causes of water leakage from the single-layer well wall of the drilling method were analyzed with the information of hydrogeological characteristics of mine. It was found that the main reason of water leakage at the sub-well wall of Xutong Mine was that the high-pressure groundwater recharged from the aquifers flowed into the well through the gravel packing layer with great pore connectivity, after the corrosive effects of groundwater jointly penetrated the stubs of well walls. Then, the feasibility and safety of using post-wall grouting and ground drilling grouting for water leakage control in the wall of sub-well wall in Xutong Coal Mine were compared and analyzed. Post-wall grouting of reinforced concrete single-layer well walls constructed using the drilling method in fluvial sand layer was found to pose a high safety risk, affecting the normal lifting of wellbore and risking the reoccurrence of water leakage. Ground directional drilling grouting technology had a large grouting volume, and the pores in the gravel filling layer behind the wall can be fully filled by cement slurry, improving the leakage prevention and bearing capacity of the wellbore, and the construction personnel operated on the ground, which was safe and did not affect the normal lifting of the wellbore. Finally, the ground directional drilling grouting technology for water leakage control of coal mine wall in deep alluvium was proposed and demonstrated. A total of 130.9 m³ of cement slurry was injected into the two boreholes, which completely filled the pores space between the gravel of the filling layer behind the wall of the layer from 94.00-131.40 m, and successfully blocked the water outlet point at 94 m downhole. No further water leakage from this section of the well wall had been observed on site over a long period of time. The research results shown that, the ground directional drilling grouting technology had good control effect and high safety for the water leakage of coal mine drilling well wall in deep alluvium. The research results can provide a certain reference for the water leakage control of coal mine drilling well wall in deep alluvium.