Experimental Study On High Thixotropic Filling Slurry In Cavitary Gob Area

With the massive exploitation of coal,there are a large number of goafs in all major coal mining provinces.At present,the most common treatment method in the goaf is the full filling pressure grouting method,which injects filling material into the goaf through drilling,and the stone formed after the coagulation will support the overburden and the surface to achieve governance goals.When Cavitary Gob Area is treated by the full filling grouting method,the conventional slurry is wasteful due to excessive fluidity and uncontrollable flow range and low grouting rate and large water splitting rate are likely to cause poor packing compactness and large area product water and other issues.This paper relies on the National Natural Science Youth Fund Project(51404295)and the Shaanxi Provincial Natural Science Basic Research Project(2015JQ5185),In view of the problem o of Cavitary Gob Area,and is inspired by the thixotropic cement slurry commonly used in petroleum cementing.using thixotropic properties,a new grouting material for Cavitary Gob Area is developed by means of laboratory tests and model tests.The material uses a thixotropic slurry to increase viscosity when it is allowed to stand,and the viscosity is reduced during shearing,so that it remains in a flowing state in the grouting pipe,the borehole and the pore fracture,and is transported to the gob or the pore crack at a predetermined position.The shearing effect is rapidly weakened,the viscosity is rapidly increased,and the filling material is quickly accumulated in a certain range.The thixotropic slurry overcomes the disadvantages that the fluidity of the conventional grouting material is difficult to control and is not easy to accumulate,and the slurry has a high stone rate,and the compressive strength of the stone body can meet the requirements of the gob area treatment.The following results have been achieved:(1)Selecting four kinds of thixotropic agents,such as bentonite,calcium sulfate,aluminum sulfate and ferrous sulfate,and mixed layer metal hydroxide positive electrode(MMH),from common thixotropic agents,and mixing with cement slurry to obtain different thixotropic cement slurry systems..The thixotropic properties of the four systems were tested and the thixotropic agent used herein was selected as a mixed layer metal hydroxide positive electrode(MMH).(2)Combined with the requirements of hollow goaf treatment,the author improved the static shear force method and proposed a new method to evaluate thethixotropic properties of thixotropic slurry-the thixotropic coefficient method,which solved the problem that the traditional thixotropic evaluation method does not consider the time factor.According to the thixotropic slurry performance test phenomenon and test results,high thixotropy is defined: the static shear force value at the initial moment of the thixotropic slurry is less than 100 Pa,and the static shear force value after standing for 10 min is greater than 200 Pa.A thixotropic slurry that meets the above conditions is referred to as a high thixotropic slurry.(3)Using the idea of differentiation,a model test simulating the accumulation flow of slurry in the goaf is designed.The results show that the thixotropic slurry quickly accumulates at a sufficient height within a limited flow distance,and as the slurry accumulation height continues to increase,the slurry The flow distance is gradually slowed down,and the curves of grouting time,stacking height and flow distance are fitted,and the functional relationship of the three is obtained.In summary,the thixotropic slurry studied in this paper can meet the filling requirements of Cavitary Gob Area,provide guidance for the treatment of Cavitary Gob Area and open up new ideas.