Study of Reasonable Grouting Pressure in the Process of Measuring Coal Seam Gas Pressure and Application.

Coal seam gas pressure is an important index to evaluate the risk of coal outbursts. The accuracy of measurement is closely related to the quality of hole sealing, and reasonable grouting pressure is one of the key factors to determine the quality of hole sealing. To obtain a reasonable grouting pressure, a mathematical model for slurry flow was established based on the relationship between the seepage law of the slurry and the properties of the borehole surrounding a rock. According to the conditions of the working face 11111 of the coal seam Ji in Pingdingshan No. 13 Coal Mine, the reasonable grouting pressure in the process of hole sealing and pressure measurement were simulated by COMSOL multiphysics numerical simulation software. After comparing the pressure distribution and slurry diffusion characteristics in the borehole under different grouting pressures, it is concluded that the reasonable grouting pressure is 4 MPa. When 4 MPa grouting pressure to seal the hole is used during actual engineering verification, the measured gas pressure is 2.7 MPa, which is more accurate than the result obtained under conditions of sealing with normal pressure grouting.