Research On Prestressed Anchor Grouting Reinforcement Technology And Its Application In Surrounding Rock Of Extremely Soft Coal Seam

Support for mining roadways in soft and broken coal seams has always been one of the main problems faced by coal mines.Reducing costs and improving work efficiency are the keys to supporting technology.However,the widely used anchor net support system is still difficult to work for this kind of roadway.Grouting reinforcement can effectively improve the structure of broken coal.However,the commonly used grouting materials still have the problems of high pollution,uncontrollable setting time,easy water separation and so on.This article takes the 3303-1 mining roadway of No.3 coal seam in Sangshuping No.2 Coal Mine as the research object.Aiming at the problems such as the development of broken cracks in coal gangs,difficult support and high cost,and low gas drainage rate,the proposal of "pre-stressed anchor grouting reinforcement for cracked coal and rock mass" is proposed.This paper develops a new type of self-stressed grouting material LS-1 and prestressed grouting bolts,and organically combines the bolt system with the grouting process.First,the theoretical analysis of the prestressed anchor-grouting surrounding rock mechanism is carried out.The combination of prestressed anchors and self-stressed grouting are complement each other.The self-supporting ability of surrounding rock can be greatly improved.Then carrying out Minitab orthogonal test designs and analysis on the self-stressed material LS-1 with slight expansion.And getting the best mix ratio according to the principle of each component.Carrying out the pre-stressed anchor grouting simulation test in the laboratory for the reorganized "new coal body" of the coal blocks retrieved on site.The anchored and grouting parameters are obtained through the uniaxial compression test,for example,the optimal prestress 50KN,etc.Through the uniaxial-acoustic emission test,the performance of the coal specimen before and after prestressed anchor grouting is analyzed in detail.According to the geological conditions of 3303-1 roadway,this paper uses FLAC3D to simulate the analysis of the original support scheme and prestressed anchor grouting on the stability of the roadway and the influence of mining disturbance.Finally,the results of on-site monitoring of the bolting force,borehole TV and gas drainage rate of the 100m roadway section of the two schemes show that the prestressed anchor grouting has a better control effect on the broken coal gang.It can improve the structure of broken coal gang in 3303-1 roadway and restore the integrity of fractured coal body.And increase the gas extraction rate by 42.68%.It can save the total support cost of about 4.9 million yuan per year than the original support plan.It can also save gap construction and reduce the number of construction personnel,12.So,it greatly reduces the probability of dangerous accidents.The research in this paper can provide reference experience for the other same type roadways,and lay a good foundation for the application of prestressed anchor grouting in geotechnical engineering such as tunnels,mines and slopes.