Numerical Simulation Of Rock Surface Stress Drilling Detection

In deep mining, rock burst, collapse, large deformation and other geological hazards are the main factors that have influence on mining safety and efficiency, which is at present one of the hot research issues in rock mechanics and mining field. Accurate measurement of in-situ rock stress of deep mining area, stopes of the mining disturbance area and secondary stress field of surrounding rock, is the important means that determines the stability of rock mass and predicts and prevents geological disasters.In this paper, the numerical method is used to study the problems of measuring surrounding rock surface stresses by the method of loophole-drilling release. The physical quantities in the hole-drilling release process of detecting surrounding rock surface stresses were defined and the expressions that describe the relationships of physical quantities were given. The release laws that different initial principal stresses combinations cause and the effects that the Young’s modulus and Poisson’s ratio have on the curves of stress and strain release rates have been discussed.The results indicate that stress and strain release rates are faster at the beginning of drilling; however, as the depth of drilling increases, the rates become lower and stresses primarily finish releasing after the drilling depth reaches1.6d. The main factors that influence the release rates include the depth of drilling, initial principal stresses and the initial value’s ratio of principal stresses, etc. The hole-drilling release laws described by the dimension-less variables-stress release rates and strain release rates, aren’t influenced by initial stresses and the Young’s modulus; but there are different release curves along the two principal directions; moreover, the curves are both influenced by the Poisson’s ratio at different degrees.Further Studies on the relationship of the dimension-less variables-the release value’s ratio of the principal strain (△nε) and the dimension-less variables-the initial value’s ratio of the principal stress (n0σ) were made and through this quantity choose the feasibility of the release curve. Therefore, the△nε-n0σ curves corresponding to different borehole depth were obtained and the process of measuring surrounding rock surface stresses by the method of loophole-drilling non-complete release was given.