| The key aquifuge plays a key role in safe mining and water resource protection of lower group coal in North China type coal fields,and can effectively prevent water inrush disaster from the floor strong karst aquifer,however,the key aquifuge loses its water barrier function caused by fault cutting and karst development.The key aquifuge can be repaired and strengthened by grouting reconstruction technique,which can realize the purpose of safe mining and protection of karst water resources.The limestone fractured aquifer is an important component of the key aquifuge,the study of the diffusion mechanism of slurry in fractured aquifer has important theoretical significance and engineering value for perfecting grouting theory and improving the grouting transformation effect of fractured aquifer.Based on the grouting transformation of lower coal floor fractured aquifer as engineering background,a key scientific issue on the slurry diffusion law under slurry-rock mass coupling effect is proposed around two engineering issues: how to determine the slurry diffusion area and ensure the grouting effect.In this thesis,rock mechanics,elastic mechanics,seepage mechanics and other relevant theories are comprehensive applied,then the research using the method of theoretical analysis,laboratory test,numerical simulation and field practice is concentrated on three key points,namely the single fracture grouting diffusion law considering slurry-rock mass coupling effect,the mechanism of slurryrock mass coupling effect of fractured group and the characterization of influencing factors,and the grouting treatment technology for fractured aquifer based on the slurryrock mass coupling effect.The following innovative research results are achieved:(1)A single fracture grouting diffusion theoretical model is established that considers the coupling effect of slurry flow and rock mass deformation.The spatial distribution characteristics of slurry pressure and fracture aperture in the slurry diffusion direction are analyzed,and the effect rules of slurry-rock mass coupling effect on slurry diffusion is revealed.The comparison with the grouting model with constant fracture aperture indicates the necessity of considering the slurry-rock mass coupling effect in the design of grouting pressure.(2)A visual single fracture slurry diffusion test system is independently developed,which considers the slurry-rock mass coupling effect during grouting process,and can real-time display the slurry pressure and fracture aperture changes at different fracture locations.The nonlinear flow law of slurry in fracture is revealed through grouting simulation tests,and the sensitivity of factors affecting the slurry-rock mass coupling effect is analyzed.The system can also be used for the study of gas seepage-rock mass deformation coupling effect.(3)An analytical model and a numerical simulation model for fracture group grouting considering slurry-rock mass coupling effect are established.The characteristics of the flow velocity and pressure distribution of slurry in fracture group with different aperture combinations are analyzed,and the effects of slurry-rock mass coupling effect on path pressure,rock slab deformation between fractures,and the variation of fracture aperture are obtained.The mechanism of the phenomenon of slurry particle infiltration at fracture entrance caused by rock slab deformation is revealed.(4)Aiming at the engineering example of grouting transformation of the fracture aquifer of a typical mine,a high and low pressure grouting method for grouting along the original grouting hole and then sweeping the hole is proposed,and the grouting parameters are optimized and designed,according to the mechanism of slurry-rock mass coupling effect.The purpose of aquifer reconstruction and is achieved,and the effectiveness of the high and low pressure grouting method is verified,providing a reliable reference for innovative fracture aquifer reconstruction technology.There are 127 figures,20 tables and 199 references in this dissertation. |
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