The Peak Stress Region Front Boundary Determination In Mining Roadway

The stress concentration hazard mainly refers to the mining dynamic phenomena which the coal mass with in the high stress region of the roadway will release significant amount of energy to trigger the violent vibration and the rock burst once the boundary of the high stress region has disturbed by multi reasons. As the excavation depth of the coal mining in China now increased magnificently, the hazard of stress concentration has become the critical threaten in the coal mine safety managements.The throttle issue of solving this hazard problem is how to determine the boundary of the high stress region swiftly and effectively. This paper based on the theoretical analysis, the proportional simulation experiment and the in-situ measurement at Beijing Chang Gou Yu Coal Mine. It successfully discussed a new determination method within the implementation of low strain dynamic pile integrity detector.In the theoretical analysis, we discussed the fracture development and the fracture angle under the coal seam roof deflection loading model with the Griffith Fracture Theory and Column-Mohr Stress Circle Theory. The pattern of stress wave propaganda in one-dimensional model also has been discussed. The magnitude of the stress wave speed has been calibrated under different circumstances before the implementation of PID for in-site measurement has been done.In the proportional simulation experiment, we build up the model which the thickness of each layer in this model proportional to the depth of each coal seam.Meanwhile we implement the external normal load to simulate the gravity force over the top of the cover layer to evaluate the final cracks development in the horizontal direction in this model.During the in-situ measurement, we have been collect large amount of the geological information. In this coal mine, the stress applied of the covering rock layer is relatively high and the toughness is indifferent for each adjacent coal seam. Based on that we establish the “Carrying Pole Model” and the one dimensional bar model which perpendicular to the mining roadway wall. We set the different Young’s Modulus between the frond and rare control volume to determine the scatting range of the fractures in the coal seams. Based on the reflection signal which collected by the pileintegrity detector, we would be able to define the boundary between the elastic and plastic segments eventually.