Experimental Study On Mechanical Properties Of Fiber Reinforced Grouting Materials

Since entering the 21st century,with the increasing mining depth of underground engineering and coal mines in China,the deep surrounding rock is broken,which seriously affects the production safety.Therefore,improving broken rock mass has become the key point of roadway reinforcement research.Grouting reinforcement technology has the advantages of short time-consuming,low cost,simple construction and good effect.It has become an important method to strengthen broken rock mass.In the process of grouting reinforcement,there are many problems with traditional grouting materials,such as poor grouting effect and poor mechanical properties,and cement particles cannot be injected into pores or cracks with a radius of about 0.2mm.Therefore,the systematic research on carbon fiber reinforced grouting materials has practical significance.In this paper,carbon fiber reinforced grouting materials are systematically studied.From the aspect of raw materials,the types and proportion of raw materials are screened through specific tests.In this paper,the basic physical and mechanical properties of carbon fiber reinforced grouting materials with different carbon fiber content are studied,combined with SEM analysis,and the best mix proportion is obtained.Through the indoor grouting model test,the mechanical property test of the grouting block is carried out.Combined with SEM and industrial CT,the failure mode of each component of the grouting material and the crack evolution law of the grouting body under uniaxial compression are analyzed.The main conclusions are as follows:(1)The basic physical property test of carbon fiber reinforced grouting material shows that the content of carbon fiber has little effect on the fluidity,setting time and water precipitation rate of grouting material;The stability increases obviously with the addition of carbon fiber.(2)The mechanical property test of carbon fiber reinforced grouting material shows that when the content of carbon fiber is 1.0%,the compressive strength,tensile strength and dynamic compressive strength of carbon fiber reinforced cement mortar are the highest.(3)Through the fiber injectability test,it is proved that the carbon fiber in the carbon fiber reinforced grouting material has good injectability at the fine cracks.The microstructure of grouting materials was observed by SEM,the microstructure and morphology of cement hydration products were determined,and the microstructure enhancement mechanism and microstructure formation process of grouting materials were revealed.(4)The mechanical property test of grouting block through indoor grouting test shows that the compressive strength and dynamic compressive strength of grouting block with carbon fiber content of 1.0% are lower than that of cement mortar block;The tensile strength of grouting block with carbon fiber content of 1.0% is higher than that of cement mortar block with carbon fiber content of 1.0%;With the increase of curing age,the compressive strength,tensile strength and dynamic compressive strength of grouting block under different carbon fiber content are increasing;Under the same curing time,the compressive strength,tensile strength and dynamic compressive strength of grouting block with carbon fiber content of 1.0% are greater than those of non fiber grouting block.(5)The results show that the carbon fiber is closely combined with the matrix material,and the irregular end face and irregular structure of carbon fiber are conducive to the role of carbon fiber.The failure mode of carbon fiber is that carbon fiber is pulled out.The VAE lotion in the damaged grouting block is still reticular in the matrix material,connecting the two ends of the crack.(6)The three-dimensional fracture characteristic structures such as the number and volume of cracks in the grouting block are analyzed by CT.The results show that the three-dimensional fracture fractal dimension is consistent with the change law of fracture volume in each stage of CT scanning;The grouting data of different stages are obtained through CT test.It is determined that the failure process of grouting body under uniaxial loading is divided into five stages: initial defect expansion stage,compaction stage,elastic deformation stage,crack generation and expansion stage,crack accelerated expansion and penetration stage.