Deformation And Failure Characteristics And Control Mechanism Of Surrounding Rock In Water-rich Coal Roadway

Groundwater is long-term stored in the structural surfaces and pores of the surrounding rock around the coal roadway.The complex physical and chemical reactions between the groundwater and the coal matrix have caused damage to the internal structure of the surrounding rock,deterioration of macro-mechanical properties,reduced bearing capacity,and increased roadway deformation and damage,which seriously affects the safety construction of coal mines.Therefore,it is of great theoretical and engineering significance to study the deformation and failure characteristics and control mechanism of surrounding rock in water-rich coal roadway.Laboratory test,theoretical and numerical analysis,and field monitoring were all used in this study.The true triaxial mechanical properties and degradation mechanism of coal in a water-rich environment were analyzed from the macro and mesoscopic perspectives.The deformation and failure characteristics of the surrounding rock in water-rich coal roadway considering the deterioration of the coal strength parameters were studied.The composite cement slurry was optimized.The reinforcement mechanism of grouting to the cracked coal and the control mechanism of the surrounding rock in water-rich coal roadway.The surrounding rock control technology of the water-rich coal seam roadway with grouting was proposed.The main innovative results are as follows:(1)Experiments on the true triaxial compression mechanical properties of coal at different immersion times were carried out,the macromechanical behavior and spatial fracture evolution law of the immersed coal under true triaxial condition were obtained,and the deterioration law of coal strength parameters with the immersion time was revealed.Combining with the changes in the microscopic morphology,pore structure and mineral composition content of the coal before and after water immersion,the microscopic mechanism of coal mechanical properties deteriorated by water were revealed.(2)A mechanical model of the surrounding rock of a water-rich coal seam under a non-uniform in-situ stress field was established,and the strength parameter deterioration coefficient of the water-rich coal was introduced.The stresses,displacement,and plastic zone radius of roadway surrounding rock in water-rich environment were derived considering the deterioration of coal strength parameters.The influence law of strength parameter deterioration coefficient,lateral pressure coefficient,and support resistance on the deformation and failure characteristics of the roadway surrounding rock in water-rich environment were revealed though the case study.(3)Orthogonal experiments on the viscosity,fluidity,water separation rate,setting time,and stone strength of different slurry were carried out.And a stable,safe,and reliable composite cement slurry material was obtained.The self-developed grouting test system was used to carry out the grouting test of the fractured coal body.Combined with ultrasonic velocity measurement and true triaxial compression,the wave velocity characteristics,true triaxial strength,deformation,and fracture characteristics of the composite cement slurry added to the solid were analyzed,and the mechanism of grouting reinforcement for fractured coal was discussed.(4)Numerical calculation models of grouting support for roadway surrounding rock in water-rich coal seam was established by using FLAC^3D software.The influence of grouting on the stresses,displacement,and plastic zone in roadway surrounding rock was analyzed.And the control mechanism of grouting on the roadway surrounding rock in water-rich coal seam was revealed.Aiming at the specific engineering geological conditions of the water-rich coal roadway,a surrounding rock control technology with grouting was proposed,which has achieved good control effects and provides scientific basis and technical guidance for ensuring the long-term stability of the water-rich coal roadway surrounding rock.101 figures,10 tables,and 209 references are included in this dissertation.