Study On Crack Propagation Of High-energy Gas Permeability Enhancement Process

At present,coal is still the main energy in the energy structure of our country.As long as the coal is mined,there will be gas gushing out,and the permeability of 95% or more high gas coal fields in our country is very low.The key to the success or failure of gas drainage is to solve the low permeability of coal seam.The main idea of gas control in China is "regional gas drainage".However,in the coal seam with high gas and low permeability which does not have protective layer mining,it is necessary to take local pressure relief and antireflection.Some measures,such as drilling hole,cutting joint pressure relief and antireflection,hydraulic antireflection,drilling blasting antireflection and so on,have achieved certain results,but there are still some shortcomings in the practical application of the project.High energy gas permeability enhancement technology is a technology emerging in recent years.Compared with conventional coal seam local pressure relief and permeability increasing method,high energy gas permeability not only fully takes into account their advantages,but also abandons their disadvantages,so it is a promising local pressure relief and permeability increasing technology.However,the theoretical study on the mechanism of high energy gas shock antireflection and coal breaking lags behind the experimental study.Most of the previous studies have focused on explaining the construction technology of cracking,the construction process of cracking and the changes of gas extraction amount before and after antireflection.There are few studies on the mechanism of high-energy gas cracking and crack propagation,which are usually regarded as homogenized bodies to carry out relevant work,and the influence of joints and fractures in coal bodies on crack propagation in antireflection process is not considered.In this paper,a self-made experimental system of air pressurization,which is used to simulate the crack caused by high energy gas impact,is used to destroy the concrete specimen.According to the test results of high energy gas impact on concrete sample,Select reasonable numerical model parameters.Secondly,by using RFPA2D-dynamic finite element software,considering the nonuniformity of coal medium,taking the test parameters of high-energy gas impact on concrete sample as standard,the high-energy gas impact increase is considered as the result of impact triangle wave.The obtained numerical model has a good consistency with the results of similar experiments,which provides a numerical analysis method for the further study of high energy gas shock antireflection.Thirdly,the numerical experiments on the process parameters(crack energy,hole spacing)of high energy gas shock antireflection process are carried out using the above numerical model.The results show that the crack energy(load peak value)of high energy gas shock antireflection process is obtained.The loading rate)can control the fracture zone and the number of cracks,and the different distance between the holes can control the cracks between the holes.At the same time,the formula of the distance between the holes and the damage area of the cracks is obtained.Fourthly,the influence mechanism of different joint parameters on the crack propagation of high energy gas shock antireflection crack is studied,and the joint parameters(angle,angle)are established for the numerical test of antireflection crack propagation of high energy gas shock under the condition of jointed parameters,and the influence mechanism of different joint parameters on the crack propagation of high energy gas impact antireflection crack is studied.The relationship between joint angle,length and antireflection crack area is quantified in the mathematical model between length and crack area.Finally,the research results of the full text are objectively analyzed,summarized and summarized,and the shortcomings and prospects are put forward.It is hoped that the research results of this paper can be used to study the crack propagation of high energy gas impingement and antireflection crack,and it can be used as a guide for engineering design and construction of high gas and low permeability coal reservoir.