Computation of Mining Induced Floor Additional Stress and Its Application

In order to study the stress distribution and deformation law of the floor after the coal seam is excavated,using the elastic theory in the form of increment,we obtain the additional vertical stress,horizontal stress,and shear stress of any point through the MATHCAD software.The distribution map of additional stress of the floor is drawn.According to Mohr-Coulomb criterion,the additional stress is converted to principal stress,then the failure depth of the floor is predicted with the introduction of the rock strength index and the failure depth of 1022 working face in Taoyuan coal mine is in-situ tested with the hydraulic test method.The results show that the additional concentrated stress near the coal wall decreases gradually with the increase of the depth of floor,and the failure depth of the floor computed is 12% different from that obtained in the in-situ test,showing a high reliability of the theoretical computation.The results in this paper can provide a theoretical basis for the control of water-inrush in the coal mining under pressure.