In-situ stress has an important influence on the stability of underground rock mass, hence knowing the geostress distribution of it is the basis for rock engineering safety, especially in coal mine. In recent decades, the in-situ stress testing techniques, which is not very successful and advantageous when be operated in coal mine with relatively narrow space and low strength sedimentary rock, have been developed for hard rock. As a expansion from in-situ testing results, stress field inversion although been focused on by more investigators recently, cannot respond to the rock burst prevention in practice, despite of numerous inversion theories.
Comparing multiple factors linked to coal bump, we studied the stress induction principle of it. In response to traditional in-situ stress testing with disadvantages of long testing period, poor applicability for coal mine and discrete results, we developed the rapid in-situ stress testing equipment which is 42mm aperture and 3d test period based on the principle of hydraulic fracturing, and 3D stress field inversion software by the multiple linear regression analysis, making the stress field of coal mine obtained more efficiently and practically.
In conclusion, stress is the most crucial factor for coal burst, prior to structure which produce an additional stress, and bursting liability which lower the bursting critical stress. An in-situ stress testing device suitable for small aperture in sedimentary layer in coal mine, was developed successfully to obtain geostress results of several segments in one drilling hole efficiently. The 3D stress field inversion technology was proposed and corresponding software was programmed for practical cases. This technology has been widely applied for impact risk evaluation, pre-mining layout optimization, dynamic processing analysis, etc., which is of great significance to the safety of coal mines.
As in-situ stress is the basis of underground engineering research, scholars have been working on accurate and rapid measurement of geostress for many years and developed a variety of testing methods [Wu et al. 2018; Li et al. 2017 and Wu et al. 2016]. Among them, hole stress relief method is a widely used and mature test in coal mine [Cai et al. 2008], although with practical problems such as long test time, low success rate and poor adaptability for weak strata [Kang et al. 2016]. To figure out problems above, Hongpu Kang, the academician of China Coal Research Institute, developed in-situ stress measurement technology with 56 mm aperture via hydraulic fracturing, which was applied successfully in many coal mines in shanxi and shaanxi province [Kang et al. 2007]. However, the aperture of geostress testing is still large, making it inconvenient to operate in coal mine with small shaft space. Therefore, we had been pondering a smaller aperture to adjust to the condition of coal mine.