Surface borehole synthesis tension deformation fracture time-space rule

In order to release the tension and shear effect of the superjacent rock strata movement during excavation in coal mine,protect the surface borehole case from fracturing fast and make a good use of the surface borehole during goaf methane drawing,a common synthesis tension deformation fracture model was set up based on the synthesis tension effect of the rock strata,and the deformation rule of the surface borehole case with time and space was researched.The results suggest that,to reduce the deformation the surface borehole should be built between the boundary of the stope and the knee of subsidence curve.At the same time,a 3DEC simulation model and an engineering example were carried out to examine the rules of theoretical model.The result suggests that the model and the rules accord to the test and have good building and protection engineering application values to the surface borehole.