Experimental Study On The Failure Characteristics Of Rock Under Different Confining Pressures And It's Grouting Reinforcement

It is one of the most common problems of underground engineering that the excavation of underground engineering induces the damage and failure of rock mass,and then causes the instability of rock mass structure.Therefore,the failure characteristics of rock under the action of stress has always been the focus and hotspot of rock mechanics research.Effective reinforcement and support means is the key to maintain the long-term stability of underground engineering,and grouting is an important technical means to effectively improve the mechanical and permeability properties of rock mass and improve the stability of underground engineering structure.In this paper,a series of studies are carried out around the failure characteristics of rock force and the grouting reinforcement effect of damaged rock.The mechanical parameters such as the stress failure characteristics of yellow sandstone under the condition of triaxial compression and the peak strength,recovery ratio and strength characteristics of grouting added solid after the failure are studied.The failure characteristics of rock force and the grouting reinforcement effect of grouting on the stress damaged rock are analyzed in depth.The main research results and conclusions are as follows:(1)The results show that with the increase of confining pressure,the peak strength,peak strain,modulus of elasticity and modulus of deformation of Yellowstone show an obvious upward trend,and confining pressure has an obvious control effect on rock deformation and strength;with the increase of confining pressure,the failure mode of rock will change from tensile failure to shear failure The box counting dimension is used to characterize the fracture characteristics of the surface of sandstone samples damaged under different confining pressures.The results show that the fractal dimensions of 0-8mpa are 1.39,1.30,1.26,1.22 and 1.21,respectively.The fractal dimension of damaged rock sample surface decreases with the increase of confining pressure,and the order degree of rock failure increases.Confining pressure has a certain control effect on rock failure morphology.(2)The viscosity time-varying characteristics of urea formaldehyde resin slurry are studied.The results show that the higher the oxalic acid concentration is,the shorter the slurry gelling time is.When the oxalic acid concentration is the same,the larger the volume ratio is,the longer the slurry gelling time is.According to the viscosity and solidification characteristics,the appropriate ratio and oxalic acid concentration should be selected in the actual project.(3)The strength and recovery ratio of grouting plus solid increase with the increase of confining pressure.The strength of 0-8mpa grouting plus solid is 7.1,17.5,31.9,32.3 and 43.2mpa respectively.The recovery ratio of grouting plus solid is about 0.1 under uniaxial condition,about 0.15 under 2MPa condition,and 0.25,0.23 and 0.27 under 4-8mpa condition respectively.Mohr Coulomb is strong According to the criterion of degree,the peak strength of yellow sandstone under different confining pressure is fitted with grouting plus solid,and there is still a certain gap between grouting plus solid cohesion and intact rock.(4)The fractal dimension shows a downward trend with the increase of confining pressure,and the downward trend gradually slows down.The fractal dimension tends to be stable,while the strength and strength recovery ratio show an upward trend with the increase of confining pressure,the rising trend of strength recovery ratio gradually slows down,and the strength recovery ratio tends to be stable.