In-situ stress distribution law in coal-bearing stratum under control of reverse fault

Abstract

To deepen the understanding of the distribution characteristics of geostress in coal-bearing stratum under the control of reversed faults, physical simulation experiments based on the similarity principle were conducted using a self-developed large-scale true triaxial instrument called the “Mine Geotectonic Simulation Experiment System”, with consideration for depth, dip angle, and fault drop. In conjunction with numerical modeling, we examine the disturbance width and the geostress's distribution law in various scenarios. The results show that: ① The geostress disturbance width in the hanging wall is greater than that in the footwall, and both of them diminish as depth increases. The 45° fault has a narrower disturbance width than the 60° fault. At 500, 1 000, and 1 500 m depth, the former is 35.72, 27.33, 10.71 cm, and the latter is 47.03, 32.15, and 17.85 cm, respectively. ② A clear instance of the maximum horizontal stress (σH) at nearby faults concentrating stress. The greater the dip angle, the greater the concentration of stress, when the angle is greater than 45°. At 500, 1 000, and 1 500 meters depth, the stress concentration coefficients of the No.4 measurement stations at the 45° fault’s footwall are 0.95, 0.94, and 1.15, which are close to the regional stress field. These of 60°fault are 1.11, 1.44, and 1.42, respectively. ③ Far from the fault, in the undisturbed zone, the σH deflection angle is nearly less than 15°. The greatest deflection angle in the disturbed zone is around 90°, and is governed by dip angles. The maximum deflection angle appears close to the footwall fault in 45° fault, but it appears farther away from the hanging wall fault in 60° fault. ④ The width of the disturbance is clearly greater when the drop is greater than the coal seam’s thickness, particularly in hanging walls. In greater elasticity modulus strata, zones of stress concentration are found, and each measurement site in the coal seam has a very large σH dispersion.

Keywords

• in-situ stress distribution
• coal-bearing stratum
• reverse fault
• stress concentration
• deflection