Methods for grout injection repair and water retention in goaf

A method for grout injection repair and water retention in a goaf, comprising:

• determining extraction information on the goaf and a coal seam;
• forming a barrier wall through performing a first grouting operation at a side of the goaf near the coal seam based on the extraction information, including:
• determining a first cross-sectional pattern of the goaf based on the extraction information;
• forming, starting from the coal seam near a corner of the first cross-sectional pattern, a first trajectory line through extending along an edge of the first cross-sectional pattern into the goaf;
• wherein first trajectory lines corresponding to each corner of the first cross-sectional pattern connect to each other to form a first grouting pattern;
• and performing the first grouting operation according to the first grouting pattern to form the barrier wall, including:
• controlling, at a ground area corresponding to a starting point of each of the first trajectory lines of the first grouting pattern, a drilling device to perform vertical drilling based on a vertical drilling parameter to obtain a plurality of first grouting holes;
• for each of the plurality of first grouting holes, controlling the drilling device to perform horizontal drilling along a first trajectory line corresponding to the first grouting hole based on a horizontal drilling parameter to obtain a plurality of first branch holes;
• controlling a plurality of low-pressure grouting pumps to perform the first grouting operation on each of the plurality of first branch holes based on a first grouting pressure to form the barrier wall;
• wherein a distance between the first trajectory line and an adjacent edge of the first cross-sectional pattern is less than or equal to a target grouting radius;
• and a distance between a starting point of the first trajectory line and an adjacent edge of the first cross-sectional pattern is greater than or equal to the target grouting radius;
• performing a second grouting operation to complete a grout injection repair from outside to inside in the goaf based on the extraction information, including:
• determining a second cross-sectional pattern of the barrier wall and a lowest point of a water level in the goaf based on the extraction information;
• forming, starting from any corner of the second cross-sectional pattern, a second grouting pattern through spirally extending along an edge of the second cross-sectional pattern toward the lowest point of the water level;
• and performing the second grouting operation according to the second grouting pattern to complete the grout injection repair, including:
• controlling, at a ground area corresponding to a corner of the second grouting pattern, the drilling device to perform vertical drilling based on the vertical drilling parameter to obtain a plurality of second grouting holes;
• controlling the drilling device to perform horizontal drilling on the plurality of second grouting holes along at least one second trajectory line based on the horizontal drilling parameter to obtain a plurality of second branch holes;
• controlling a plurality of high-pressure grouting pumps to perform the second grouting operation one by one on the plurality of second branch holes from outside to inside in the goaf based on a second grouting pressure to complete the grout injection repair;
• wherein the first grouting pressure of the first grouting operation is less than the second grouting pressure of the second grouting operation;
• the second grouting pattern includes a plurality of second trajectory lines connected end to end, and a distance between a plurality of second trajectory lines parallel to a same edge of the second cross-sectional pattern is less than or equal to two times the target grouting radius;
• and a distance between a second trajectory line located at an outermost portion of the second grouting pattern and an adjacent edge of the second cross-sectional pattern is less than or equal to the target grouting radius.