Field Trial of Distributed Acoustic Sensing in an Active Room‐and‐Pillar Mine

A distributed acoustic sensing (DAS) array consisting of three overlapping loops of cable was deployed in an active limestone and dolomite mine to sense ground vibration and examine the potential of DAS for seismic monitoring in active mine environments. The three cable loops were coupled to the mine floor in different ways: The first one was cemented into a shallow groove; the second one was covered with 2 cm of fine sand; and the third one was just loosely laid on the floor. The cemented cable loop provided the highest fidelity signal, and the cable loop loosely laid on the floor suffered from stronger noise and signal distortion. The maximum detectable distance for a 208 J weight-drop source was approximately 100 m, which was comparable to that for the horizontal component of a geophone. Two blasts were also recorded and located with this small array. Tomographic methods utilizing surface wave arrivals from the weight-drop source and differential P -wave travel times from the two mine blasts were applied to demonstrate the feasibility of imaging seismic structures with DAS observations. Uncertainty in picking arrivals, insufficient ray coverage, and strong directivity response of the DAS cable limited the resolution. Nonetheless, it appears that use of a properly installed and designed DAS array is practical for monitoring seismicity and seismic velocity changes in an active mine.