Study On The Deformation Fracture Mechanism Of The Surface Borehole With The Excavation Disturbance

Surface borehole well is a simply and high performance method to drawing coal bed and goaf gas which controlling and making good use of the coal mine gas. But the coal extraction affects the surface borhohle well greatly. When the working face pass near the surface borehole position the borehole well often fractures fast and the surface borehole won't be made a most of utility. So base on the National Great Research Foundation of China (973 Programs)"Mechanism of coal and rock'gas dynamic disastrous evolution", and the National Technology Support Program of China"Key technologys of surface borehole drawing coal bed and goaf gas", this thesis give a study on the surface borehole well fracture mechanism in the following aspects:(1) Based on the ground subsidence rule and composite rock beam deformation rule, shear slippage rule of rock strata interlayers and compression deformation of rock stratum over the coal mining district was analyzed, the composite equivalent rock beam model under extraction disturbance was set up and gain the distribution rule of equivalent composite rock beam interlayer slippage and rock stratum compression deformation.(2) Based on the surface borehole well collapse forms this thesis set up the rock strata interlayer shear slippage model and rock stratum compression deformation model and analyzed the fracture mechanism. The interlayer slippage"S"mode and rock stratum compression ellipse mode of surface borehole was gained.(3) Based on the rock strata movement rule under extraction disturbance and the surface borehole fracture model this thesis analyse the surface borehole rock strata interlayer shear slippage and rock stratum compression deformation distribution rule in the incline of the coal mining district and the time variety rule with the extraction. This will give guide for selecting the surface borehole's engineer positions.(4) The effect of geo factor such as key stratum, thick rock stratum and thick surface soil layer and extraction technicque such as stope dimension, roof contol method and extraction velocity to the surface borehole fracture was analized. This will give a theory reference for protecting measures making.(5) With the similar material tests and 3-D numeric simulation tests the rock strata movement rules, surface borehole deformation fracture rules, its time and space rules and the rock strata physical characteristics effect was give a check analysis.(6) With the examples of surface borehole in Xieqiao Coal Mine of Huainan Minging Industy the theoretical model was given a checking and applying.(7) Gaining the surface borehole position selecting principle, the surface borehole protecting methods and its design consideration.