Sonic wave testing technique for surrounding rock loose circle

This paper introduces the theory and methods of sonic wave testing technique used in measuring the surrounding rock loose circle. And this testing method by acoustic in single hole was used in the Chang Gou-yu coal mine, from the velocity curve with changing depth of hole the thickness of the surrounding rock loose circle was obtained. Based on the loose circle theory, the support parameters of the roadway could be provided by the thickness. Therefore, the sonic wave testing technique is fast and accurate in testing the loose circle, also it has good practicability and extensive application prospect.