随着采掘作业的进行,岩层压力也发生变化。液压枕就是监视这种地压变化的一种计量仪器。这种仪器大多数只能监测单一方向的垂直压力,再加上其它的一些优点,即使在含有大量微小裂隙的岩层中,也能准确地测出地压变化。 As extractive operations progress, rock pressure also changes. Hydraulic pillow is a kind of measuring instrument to monitor the change of underground pressure. Most of these instruments can only monitor the vertical pressure in a single direction, plus other advantages, even in the formation containing a large number of tiny cracks, can accurately determine the pressure changes.