Study On Analogue Of Characteristics Of Gas Emission From Coal Drilling

The characteristics of gas emission from drilling is an important indexes for the coal and gas outburst prediction,that what depend on a series of physical mechanical factors(coal seam permeability;gas pressure;buried depth;geological structure)and factors of procreative technology(drilling arrangement mode;drilling hole diameter;mining progress).Due to the different ground stress and coal seam gas pressure in coal mine,the law and characteristics of gas emission drilling is different.So it has great significance to study on characteristics of gas emission from drilling in different ground stress and coal seam gas pressure.On the basis of the analysis of methane flow regularity in coal seams,we establish a mathematic model,set up the laboratory determination of borehole gas emission characteristics of the experimental device and simulate mechanical properties of coal seam.Analyze the regularity of the gas emission which is in the process of rig drilling and after pore forming.Building mathematical model by using the finite difference method,using the computer compiler to simulate and calculate law of gas emission during boring.Using effective stress principle to build mathematical model based on stress state of drilling,and analyzing the chip removal law of cutting content.On the basis of using the experimental device simulation the drilling process in the pit;,we study the change rule of gas emission in the process of drilling and the changing rule of the quality of drilling cuttings of different ground stress and gas pressure.Experimental results and numerical simulation show that gas emission during boring rise rapidly on quite short time and become flat gradually in the drilling progress.When the drilling is operated to the deepest point,gas emission during boring is reached the maximum value.When ground stress and are different,previous increase amplitude and decay time of gas emission during boring are different.Gas emission during boring is changed obviously with the different gas pressure.the larger gas pressure,the more gas emission during boring,the larger previous increase amplitude of gas emission during boring;the longer decay time of gas emission during boring,and the larger previous attenuating range after drilling is finished.Drilling volume increases with increasing of ground stress,gas pressure,but drilling volume greatly influenced byground stress.