Experimental Study On Microbial Intervention Repair Technology Of Downward Cracks In Shennan Coal Mining Area

Coal resource is one of the important foundations to support the national economy and the people's livelihood,and the downward cracks caused by large-scale and high-intensity coal mining will inevitably lead to the loss of water resources and the deterioration of ecological environment in ecologically fragile mining areas.At present,the materials used to repair the downward cracks of coal mining often contain chemical additives.Although they can fill the cracks,they may also cause chemical pollution to the ecological environment.Microbial intervention remediation technology is a new environmental protection technology based on microbial induced carbonate precipitation(MICP).The purpose of this paper is to apply MICP to the repair of downward cracks formed by coal mining in Shennan coal mining area of Northern Shaanxi,through the experimental research on the key technology of microbial intervention repair of downward cracks,this paper explores a new way to realize the green development of coal resources and the effective protection of groundwater resources.In this paper,Bacillus megaterium was used to reinforce the cracks of the specimen.Through orthogonal experiments,the relationship between factors such as the composition of the filling aggregate,the concentration of bacteria liquid and the mechanical and hydraulic properties of the solidified sample was revealed,and key technical parameters were obtained.The microstructure changes of the repaired cracks were measured by scanning electron microscope,and the repairing effect of micp on the downward cracks was evaluated The R-C network model is built in the Simulink simulation system of MATLAB software to simulate and predict the change of groundwater level after the application of micp technology in Shennan coal mine area.It is found that MICP technology can repair the downward cracks in the overlying soil formed by the mining of reinforced coal seam to a certain extent,and effectively improve the mechanical and hydraulic properties of the damaged soil.With the increase of sand content in crack filling aggregate,the mechanical strength of the sample increases,but the permeability coefficient increases accordingly;adding coal gangue is beneficial to reduce the permeability coefficient,but when its content is too high,the solidification effect of microorganisms is affected;the ability of high concentration bacterial solution to repair cracks is stronger than that of low concentration bacterial solution,and with the increase of bacterial solution concentration,the permeability coefficient of the samples decreases.The results show that the ratio of gangue,clay and sand in the filling material is 1:1:2,adding a high concentration of Bacillus megaterium,filling the cracks in layers can not only effectively reduce the permeability coefficient of the crack filling material,but also improve its mechanical properties.Microbial intervention repair technology can effectively repair the downward cracks of coal seam mining without secondary pollution,which has the feasibility and broad prospect of engineering application.However,before the practical application,it is necessary to overcome the filling technical problems and further improve the restoration process and related technical system,so as to provide better technical support for ecological environment protection.