Influence of complicated faults on the differentiation and accumulation of in-situ stress in deep rock mass

Abstract

High geostress will become a normality in the deep because in-situ stress rises linearly with depth. The geological structure grows immensely intricate as depth increases. Faults, small fractures, and joint fissures are widely developed. The objective of this paper is to identify geostress anomalies at a variety of locations near faults and to demonstrate their accumulation mechanism. Hydrofracturing tests were conducted in seven deep boreholes. We conducted a test at a drilling depth of over one thousand meters to reveal and quantify the influence of faults on in-situ stresses at the hanging wall, footwall, between faults, end of faults, junction of faults, and far-field of faults. The effect of fault sites and characteristics on the direction and magnitude of stresses has been investigated and compared to test boreholes. The accumulation heterogeneity of stresses near faults was illustrated by a three-dimensional numerical simulation, which is utilized to explain the effect of faults on the accumulation and differentiation of in-situ stress. Due to regional tectonics and faulting, the magnitude, direction, and stress regime are all extremely different. The concentration degree of geostress and direction change will vary with the location of faults near faults, but the magnitude and direction of in-situ stress conform to regional tectonic stress at a distance from the faults. The focal mechanism solution has been verified using historical seismic ground motion vectors. The results demonstrate that the degree of stress differentiation varies according to the fault attribute and its position. Changes in stress differentiation and its ratio from strong to weak occur between faults, intersection, footwall, end of faults, and hanging wall; along with the sequence of orientation is the footwall, between faults, the end of faults, intersection, and hanging wall. This work sheds new light on the fault-induced stress accumulation and orientation shift mechanisms across the entire cycle.

Keywords

fault / geostress in deep / magnitude and direction of geostress / mining dynamic hazards / stress accumulation / mining optimization

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