Laboratory study on engineering geological characteristics of rocks within the fault

The basic physical and mechanical properties of the rocks within a fault zone are fundamental factors affecting fault stability and will influence the stability of strata during mining, leading to serious geological hazards. To circumvent this issue, the field tests, uniaxial compressive strength tests, splitting tests, and water immersion tests were designed and performed in this study, in which the engineering geological characteristics of the fault were investigated. The results showed that, for small variations in the bulk unit weight, there was a relatively greater variation in the water content, water absorption, and porosity of the samples collected from the fault, as compared to the other samples. Generally, all the samples exhibited low strength and a large deformation degree. Among all the samples, those collected from the fractures in the fault zone exhibited the lowest strength. And the results of energy evolution further indicted that samples from the fault zone are easy to fail. The deformation characteristics obtained from the water immersion test were different for rocks collected from different sites. The samples collected from the fault zone exhibited the greatest disintegration underwater immersion. Further, plastic deformation could be observed in all the samples owing to the significant reduction in strength caused by water, which adversely affected the ability of the rocks in the fault zone to resist water. Thus, the stability of faults should be considered during coal mining to prevent water inrush accidents caused by fault activation.