The invention is to solve a problem: the solid can not tightly seal the fractures around hole with recent technique, espetially in soft coal seam, it is difficult to seal the holes and measure gas pressure. In order to get the stable and reliable measuring results of gas pressure. The invention uses viscous liquid a sealing material, the bore holes are sealed by the rubber rings on the ends of sealed liquid. So in this system, solid seals liquid, the liquid seals gas. Sine the pressure of viscous liquid is always slightly more than the pressure of gas, the leak of gas is prevented. |