A total of 1 147 in-situ stress data sets were selected from "the data of underground coal mine environmental in-situ stress in China" to deeply investigate the relationship between the stress and buried depth of coal mine strata. This study focused on the analysis of the evolution of principal stress,lateral pressure ratio,and horizontal shear stress ( μm ) with buried depth using mechanics and mathematical statistics. The results showed that the proportion of reverse fault stress state ( σH>σh>σV ),strike slip stress state( σH>σV>σh ),and normal fault stress state ( σV>σH>σh ) was 25%,55%,and 20%,respectively. There were many data in the middle and low stress area,accounting for more than 65%. When the buried depth was 0-148 m,the three-dimensional stress in the coal mine was in the state of reverse fault stress. The three-dimensional stress state changed to strike slip stress state when the buried depth was 148-1 089 m. The three-dimensional stress state turned into normal fault stress state as the buried depth was higher than 1 089 m. The shallower of the buried depth,the more discrete the distribution of lateral pressure ratio and the greater of the ratio was. The lateral pressure ratio decreased gradually with buried depth and finally tended to a constant value. The value of Kav,KH,and Kh was about 0.6,0.8,and 0.4,respectively. The "critical depth" of coal mines was 329 m for Kav =1. A fitted formula for the relationship between horizontal shear stress μm and buried depth was proposed in this study. The μm was mainly concentrated between 0.15 and 0.35,with an average of around 0.25. The larger the μm value,the more likely the fault was to slip and became unstable. The coal mines where the μm exceeds 0.35 should be closely monitored for the stability of large faults.
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