A microseismic source location method considering diffraction used in tunnel engineering

In order to improve the accuracy of rockburst warning, it is necessary to accurately interpret the microseismic (MS) information obtained during the rockburst development process. However, the MS source location is very important for the interpretation of MS information, and the MS location method has an important impact on the location accuracy. To improve the location accuracy of MS sources, a location method considering diffraction in tunnel engineering is proposed. In this method, the shortest path length between the MS source and a sensor that does not cross the empty area of the excavated tunnel section replaces the straight path length between the MS source and the sensor for the location calculation, which can reduce the location error caused by propagation path length inaccuracy. To analyse the performance of this location method, a virtual MS source location simulation test and an in situ blasting point location test were carried out based on a tunnel project. The results show that the location method can well characterize the propagation path of MS source waves in a rock mass, thus making the location error smaller. During the in situ blasting point location test, the average absolute location error of point sources is approximately 8 m, and the average relative location error is approximately 6.72%. The location results can well meet the requirements of rockburst MS monitoring for location accuracy.