Study On The Modification Of Coal Gangue-Based Grout For Reducing Settlement Of Goaf Separation Layer In Muduchaideng Coal Mine

This paper takes the problems existing in the coal gangue-based separation grouting project in Mudu Chaideng Mine as the research object,aiming at the problems encountered in the project that the coal gangue-based grout is easy to segregate,difficult to solidify,easy to freeze in winter,and long-distance pump pressure loss.The problems of uncertain diffusion range and surface subsidence in abscission space are analyzed and studied in depth by means of laboratory experiments,theoretical analysis and numerical simulation.The main results are as follows:（1）Both polyacrylamide and bentonite can effectively reduce the water separation rate of the grout,but the modification effect of polyacrylamide is obviously better than that of bentonite.Under the condition of water-cement ratio of 1.9:1,the water separation rate of the grout is 35.6%.When the content of acrylamide is 0.3%,the water separation rate of the grout can be reduced to 3.3%;when the water-cement ratio is1.9:1 and the high-water material is 15%of the mass of coal gangue,the compressive strength of the consolidated body exceeds 1.0MPa.（2）The basic control equation and the mathematical equation of the freezing thickness of the grout are established when the grout flows in the pipeline.The antifreeze effect of organic antifreeze ethylene glycol and glycerol is better than that of inorganic antifreeze sodium nitrate and sodium nitrite.Among the four antifreezes,ethylene glycol has the best antifreeze effect.When the content of ethylene glycol is4%,the grout freezes.rate decreased by about 20%.（3）The influence of water-to-gangue ratio,pipeline arrangement and grout flow rate on the grout pumping pressure loss was analyzed,and the mathematical equation of grout flow in the pipeline was established;The pumping pressure loss of the layer grouting project is calculated.The results show that when the pumping distance is 1km,the pumping pressure loss of this project calculated by the empirical formula is3.27MPa,which is closer to the actual results of the project;The pumping pressure loss is 0.37MPa lower than that before modification,which is favorable for grout pumping.（4）According to the development law of abscission space in Mudu Chaideng Coal Mine,the discrete element software PFC^2D is used for numerical simulation,and a numerical model of 2D abscission space grouting is established,and the diffusion radius of unmodified grout and modified grout is simulated.,the results show that under the grouting pressure of 4MPa,the unmodified grout has a diffusion radius of 112m,and the modified grout has a diffusion radius of 175m;under the pressure of 4MPa and6MPa,the diffusion radius of the grout is 175m and 177m,respectively.The consumption is similar,about 28,000 m³;the surface subsidence process without grouting and after grouting is simulated.After the program runs for 500,000 steps,the maximum surface subsidence before grouting is 54.57cm.The subsidence amplitude of the stratum in the upper part of the space is greatly reduced,and the maximum subsidence amount is 4.35cm,which is significantly reduced compared with the case without grouting.This thesis contains 63 figures,22 tables,and 86 references.