Research on water prevention and control technology for mine roadway engineering crossing water-rich coal seam

To reduce the serious coal seam water hazards faced by some mines in Jurassic coalfield of northern Shaanxi Province, this paper studies the water prevention technology of the roadway engineering crossing water-rich coal seam section, taking Balasu mine field in Yuheng north area as an example. No.2 coal seam in Balasu mine field, whose fractures are well developed and closely connected, contains some high pressure and strong water-rich sections. Measures such as joint drilling and grouting engineering of surface-underground of the mine, can be taken to reduce the water hazards. To verify the mine water prevention technology under such water damage conditions, we adopted the methods of drilling exploration, curtain grouting, water chemical testing, theoretical analysis, peep in the hole, exposure and verification. Results show that the water pressure of local coal seam can be 3.81 MPa, the maximum water inflow from single borehole is about 198 m3/h. We conclude that the coal seam water plugging is completed when the single borehole pressure reaches 10 MPa by drilling high-pressure grouting. The strongly alkaline treated borehole water with a pH value range between 12.20 and 12.58 (with an average of 12.32), and the water of OH·SO4-Ca·Na type, proves that the grouting material has fully entered the coal seam cracks. The hydraulic connection between each borehole, along with the data changes of ground grouting pressure, water yield and water pressure of borehole after primary grouting and secondary borehole drilling, proves that the plugging effect is good, with a total water attenuation of more than 97.5%. The water is basically no longer out of the coal seam cracks after grouting treatment based on the direct observation from the peep of the borehole. The water inflow of the borehole in the grouting reconstruction area is less than 1 m3/h, and the water inflow of the roadway tunnelling is 1.2 m3/h when the roadway is actually exposed according to the construction verification. Thus, the coal seam water hazards in the tunnelling roadway through the water-rich coal seam section is effectively reduced. Based on the study of the coal seam water hazards reduction in Yuheng north area of Shaanxi Jurassic coal field, this paper puts forward the comprehensive water prevention and control technology of exploration drilling and ground pulping, borehole grouting, test and analysis, peer validation, which ensures the safe tunneling of the mine roadway through the No.2 water-rich coal seam section, and provides a practical reference for the prevention and control of coal seam water damage in similar mines in the area as well.