On-line monitoring of underground workings stability with use of innovative inclinometric method – Case study from Polish copper mines

The threat of loss of stability of underground workings is one of the most serious dangers accompanying underground mineral exploitation. Over the years, as the depth of the deposits increased and working conditions deteriorated, the scale of the threat increased, translating into a serious risk to the life and health of the mining crew. In order to increase work safety and at the same time ensure the possibility of effective exploitation, it is necessary to implement new, autonomous monitoring systems that inform the mining operator on an ongoing basis about possible threats. In recent years, many geomechanical measurement systems have been developed. Particular attention was paid to instrumented rock bolts that can measure stresses and deformations in the immediate roof in real time. Unfortunately, despite many advantages, devices of this type provide information only about a specific threat state, and without the installation of several devices in one place, they do not enable spatial monitoring. An inclinometer system may be a milestone in the development of geomechanical systems, which enables the measurement of deformations of roof layers in real time, and the nature of the measurements translates into the possibility of conducting spatial monitoring within the excavation using one device. This article presents the results of many years of work on the development of an inclinometric system adapted to work in underground mines exploiting deposits using a room and pillar mining method. The assumptions of the system as well as the rock failure criterion developed based on pilot measurements were described. Also the results of a multi-month post-measurement campaign conducted in all three underground copper mines in Poland were presented. As shown by previous observations, the newly developed inclinometric system for monitoring the stability of workings is characterized by measurement stability and reliability of the obtained results. Therefore, it can be successfully used in underground mines facing the risk of collapse to monitor the stability of mines in real time from the control room level.