FEM ANALYSIS ON THE ORIGINAL NON-UNIFORM STRATA STRESS OF CIXI COLLIERY SHAFT OVER 1000M DEEP

According to the structure geology, geological condition and the inspection information of bore hole, the paper analyzes the original stress existing in the km depth of Cixi colliery production area using EFM model based on gravity principal and considering the dip and fault strata structure. With FEM results, the three dimensional stress state and the relationship between the vertical and horizontal inspection lines are graphically displayed. Although the three coordinate direction stress are proportional to the depth according to the analytic solution, the curve of stress vs. depth is not continues, which is interrupted at the fault and juncture of two kind of strata. The max ratio of the two cross horizontal stress is 1.22, which occurs at the depth of 613m. Based on orthogonal analysis, the ratio of the two cross directional stresses, called non-uniform coefficient, is affected mainly by the ratio of mutual shear modules, as well as the incline angle of strata. On the same level and same strata, the stress behavior is related to the incline state, and the stress in the uphill side is higher than that in the downhill by 10^-3 to 10^-4. The stress gradient is mainly related to the incline angle of strata and it does not influence the assessment of horizontal stress.