Development of a Three-dimensional Stress Monitoring System for Coal Rock and its Application in a Mine

To conduct directed tests on the multi-dimensional stresses of coal rock mass and their evolution law, a three-dimensional stress (3DS) monitoring system is developed in this study. The monitoring system is capable of realizing active and effective coupling between stress-sensing sensor chips and coal rock mass and monitoring the multi-dimensional stresses of coal rock mass and their variations continuously and directionally in real time. The research results demonstrate that: (1) The sensor of the monitoring system can give a value that is consistent with the loading value of the press, with relatively small error and strong stability. The sensor chips in the three directions are independent of each other in the monitoring process, and the 3DS sensors boast excellent work performance. (2) The test unit composed of two 3DS sensors can measure and solve the magnitude and direction of principal stress at a point in space. Apart from its easy and convenient operation, the system is able to accurately measure the 3DSs, in view of the fact that the field measurement results are consistent with previous research results. (3) The variations of three-dimensional mining stresses share basically the same trend, but they are not exactly synchronous. The vertical stress is the first to be affected by mining. The vertical mining stress value is greater than the horizontal one, but the vertical stress concentration coefficient is smaller than the horizontal one. (4) The larger the difference between the vertical stress value and the horizontal stress value of coal rock mass is, the greater the energy accumulated in coal rock mass is. The pressure relief in the horizontal direction in the vicinity of the working face often brings about a sudden decrease in the critical value of the maximum principal stress, thus inducing rock burst. A real-time and continuous three-dimensional stress (3DS) monitoring system was developed and testedThe principal stress and mining stress of a mine were measured and obtained in the field.According to the field test results, the influence of the evolution of three-dimensional on rock burst was discussed