Experiment Research on Changes of Coal Pressure after Mining Protective Coal Seam by Field Test

In the process of mining coal in China, with the mining depth and strength increasing, many low gaseous mine changed into coal and gas outburst mine, which become the outstanding problem of restricting coal industry safety and efficient production. Recently, protective seam mining technology has been proved an effective way to eliminate coal and gas outburst. This paper focuses on measuring the gas pressure of Test mine. By accurately measuring protected coal seam gas pressure, it will find out the gas variation rule of protected seam, determine the protected range of protective seam and lay the foundation for guide the control of coal and gas outburst to measure gas pressure of the protective coal seam and find out the change law of protective seam gas. The study shows that, as the workface in protective seam advanced, Yeqing coal roof and overlying strata were affected by the mining protective seam, they became loose with more fractures, enhancing the gas permeability of coal seam. The Big coal gas released more easier due to the occurrence of more fractures, the pressure of measuring gas pressure borehole were gradually reduced to 0. So it indicates that mining protective seam had significant influence on the gas emission in the Big coal seam, resulting in the gas pressure relief of protected coal seam.