The Study On The Crack Development Law After Drilling Hydraulic With High Pressure

With the rapid development of society,the rapid increase in demand for coal energy,coal mining depth in various regions gradually increased.Coal seam depth increases,gas content increases.Low permeability coal seam high gas problem has become the main problem of coal mine production safety.High-pressure water jet punch-through and anti-permeability technology is an important technical measure to solve high gas problem in coal mining.Therefore,based on the high-pressure water jet punching technology,it is very important to study the development law of coal fissure after punching to solve the problem of high gas in coal seam.The parameters such as punching position,punching angle,punching aperture and so on were determined according to the actual situation of the mine,and the parameter values which accorded with the requirements of on-site production were determined.By using ABAQUS numerical simulation software,the fracture development model of high pressure water jet after drilling is established,and the basic parameters a nd boundary conditions are determined by experiment and analysis.Fracture along the direction of co-stress has been developed along a straight line.The development of the whole plane can be determined by the unidirectional development of fracture.By determining the position of the deflection point,the variation of the in-plane fracture density after the crack is deflected is obtained.According to the different densities,the fractal development range was divided into density grads.Using ABAQUS numeri cal simulation software,the three-dimensional trajectory of fracture development was studied.The results show that the axial strain is the main factor to change the development of axial fracture.According to the law of conservation of energy,the change of axial strain can change the rule of axial and vertical axial development.In the production,the axial strain can be reduced according to the needs,and the purpose of controlling the fracture shape can be realized.Using the scanning electron microscope technique,the measuring points of different direction and different distance from the holes after punching are analyzed.The results show that the development of cracks in the working face is consistent with simulation,which can be used to guide the production practice.