Research On Factors Affecting Coal Seam Hydraulic Cutting And Prediction Model Of Slit Depth

Gas extraction is an important way of gas disaster prevention.The permeability of coal seam is a major factor affecting in gas extraction.Increasing coal seam permeability technology has been one of the hotspots in gas extraction technology.As an effective means to improve coal seam permeability,water jet slotting has been widely used in the coal mine.Slotting depth prediction is a very important factor in estimating extraction effect and drilling arrangement.However,the depth prediction of water jet slotting depends on experience,lack of scientific and reasonable prediction model.Therefore,reserch on influencing factors of water jet slotting and establishing slotting depth prediction model is of great significance to guide the drilling parameters design and reinforcement extraction effect.Focus on slotting depth influencing factors and depth forecasting model,the research work of this paper mainly includes the following four parts:1)Effect of physical and mechanical properties of coal on slotting depthAnalysis the stress distribution of coal on water jet impact by simplified the force of water jet on coal as vertical concentration force and the process of water jet impinging on coal as Boussinesq-Flamant model.Combining with numerical simulation software,the main failure modes of coal under water jet are analyzed shear failure and tension failure.2)Influence of water jet parameters on slot depthThrough analysis the data of different pump pressure and nozzle diameter group,obtaining the conclusion that the effect of pump driving pressure is more significant.At the same time,Determination the effect of each parameter on the jet force by theoretical analysis the form of jet force.3)Study on depth prediction model of water jet slottingEstablishment depth prediction model of water jet slotting by using Loland model to simulate the mechanical failure of coal under the influence of water jet and introduction of Mohr Coulomb criterion with shear strength as the failure criterion and using water jet momentum to quantify jet impact force.4)Experimental study on water jet slotting depth prediction modelThe model prediction depth with the actual depth error is less than 10%comfirm by numerical simulation experiments and simulation of materials failure experiments and field data.The final study determined the main factors which affect the depth of water jet slotting and the establishment of the slotting depth prediction model.The prediction model is verified by experimental ground failure test and mine live test.