| Under the condition of deep mining,the surrounding rock of roadway is affected by 'three heights and one disturbance',and the dynamic disasters occur frequently,which brings great risks to the safe production of coal mines.Under the action of static load,a certain range around the surrounding rock of the roadway is in the broken zone,with low residual strength and limited support resistance.Under the influence of mining,rock fracture,blasting and other mining activities,the static load is suddenly superimposed on the dynamic load,so that the stress balance of the roadway is broken again,and the failure extends further to the deep,which may cause serious dynamic damage such as rock burst and coal burst.The engineering practice shows that the grouting and grout in the crushing area make the broken rock mass re-cemented together with a certain strength,which can provide certain support resistance for the deep rock mass and stabilize the surrounding rock mass in the crushing area.In this paper,the reasonable specimen length was obtained through the correlation test of sandstone size effect and strain rate effect on the basis of the literature review.Then static and dynamic mechanics tests about different kinds of grout and broken rock consolidation were carried out.The relationship between the strength of the grouting cement,the strength of the grain and the strength of the broken rock consolidation as well as the law of failure evolution were revealed.The mechanical mechanism of the grouting reinforced fractured rock mass was analyzed,and the dynamic mechanical constitutive model of the grouting reinforced fractured rock mass wss established.Based on the criterion of Mohr-Coulomb strength,the mechanical model of roadway surrounding rock after grouting reinforcement was established.A numerical analysis model for grouting reinforcement of roadway surrounding rock under impact load was established by static and dynamic coupling analysis.The industrial test of slurry injection was carried out.The results have certain reference value for grouting reinforcement engineering of fractured rock mass and the development of anti-impact grout.Through the study,this paper mainly drawed the following conclusions:(1)The punch velocity could be precisely controlled by adjusting the air pressure and the acceleration stroke of the punch,and the strain rates of specimens with different lengths could be approximately equal when the punch velocity was loaded in the same way as the punch length.When the aspect ratio of the 50 mm diameter sandstone specimen was between 0.5 and 0.8,the strength change caused by size effect was basically similar to that caused by strain rate.When the aspect ratio was greater than 0.8,the size effect had a much greater influence than the strain rate effect.Therefore,it was suggested that the reasonable length-diameter ratio range of sandstone specimens with a diameter of 50 mm is 0.5-0.8.(2)The failure strength of grouting concretion body was determined by the minimum value of aggregate particle strength,grout cement body strength and interface strength.The cement grouting concretion body slipped along the interface between slurry and particles and presented brittle failure.The strength of cement grouting concretion body was related to the type of cement,but not to the strength of cement.The epoxy resin stone body presented plastic failure,and the grouting concretion body formed with the sandstone was broken along the grout cement body,while formed with the coal is broken along the particle failure plane.The static strength of modified epoxy stone is lower than that of grouting concretion body,but the absorption energy and dissipation energy of modified epoxy stone are higher than that of grouting concretion body.(3)The dynamic compressive strength of cement cementing body,cement grouting concretion body and modified epoxy resin grouting concretion body increases with the increase of strain rate.The dynamic compressive strength enhancement factor of grouting concretion body shows a quadratic curve relationship with the logarithm of strain rate.The impact resistance of modified epoxy resin sandstone stone is better than that of cement sandstone stone,and the dissipated energy density is greater than that of cement stone.The dissipated energy density of cement grouting concretion body has little difference with different strength,but the dissipated energy density of modified epoxy resin grouting concretion body is related to particle strength.(4)By defining the degree of repair factor quantitative description repair effect,the results showed the effects of modified epoxy resin to repair fracture is better than that of the slurry,modified epoxy resin to repair a crack in the rock and intact rock properties approximation.However,in the case of low-speed impact,the strength obtained by cement slurry filling the cracks of sandy mudstone was higher than that of modified epoxy resin.A viscoelastic damage model with a damage body and a Maxwell body in parallel was established,which could better fit the stress-strain curve of grouting reinforced fractured rock mass under impact load.(5)Based on the Mohr-Coulomb criterion of rock failure the mechanical model of the surrounding rock of the roadway after grouting reinforcement was established.Numerical examples showed that grouting reinforcement could effectively prevent the plastic zone and high stress zone from developing into deep rock mass.The mechanical model of roadway surrounding rock under dynamic impact load was established by using static dynamic coupling analysis method.The range of the surrounding rock increased in the plastic zone of the roadway facing the impact surface and adjacent areas,and the influence of the roadway deviating from the impact surface was small.After grouting reinforcement,the high stress zone of surrounding rock can be effectively controlled to transfer to the deep.(6)The industrial test shows that the grouting cement developed for coal mine based on improving the dry shrinkage rate and reducing cohesive force of grouting material is better than Portland 425 cement in grouting reinforcement effect.Figure[138]table[20]reference[165]... |
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