The Study Of Induce-crack Mechanicals And Cranny's Development Process About Hydraulic Fracture In Mining-coal Bed

Now, The economy of our country is developing at a fast rate. It's demanding in energy sources is in great increasing. Coal is regard as the mine energy sources, the quantity in 2020 will be doubled. Gas is the coal's accompany sources, it belongs cannot regenerate lustration energy sources, so increasing gas's take out effect, and increasing using rate of gas, that is important task to improve the produce safe status and empolder undefiled energy sources.The paper carried out the theory studies on hydraulic fracture of gas mining in coal bed, and on basis of the form mechanism and engineering characteristic of the coal, brought forward the coal bed is a multistratum geologic body, and the coal delamination which forms the coal bed is many- microminiature cranny and many-hole structure, hereby, expounded the mechanics characteristic and the penetrate-rate law of coal bed and coal delamination. The paper sequentially analyzed the starting-crack mechanism of hydraulic fracture bore which lies in coal delamination or lies between two coal delaminations or through many coal delaminations.1)The starting-crack pressure and direction of hydraulic fracture bore in coal delamination lies on the magnitude of original stress and side stress coefficient;2)The starting-crack pressure and direction of hydraulic fracture bore which lies between two coal delaminations not only lies on the magnitude and state of original stress but also relates to the intensity of coal delamination and interfaceï¼›3)The starting-crack location and pressure and direction of hydraulic fracture bore which through many coal delaminations mostly lies on the intensity of furthest-weak coal delamination and interface.On basis of analyzed starting-crack mechanism of hydraulic fracture bore, analyzed the mechanics condition of quondam cranny's extending and hypo-cranny's starting-crack, compiled the program by use of MATLAB, the numerical value analysis outcome validated the correctness of theoretic analysis. In the end, on basis of summing up the control-mechanism and control-method, the paper broughtforward the idea of synthesis design on hydraulic fracture which used to mine gas in coal bed.