Polypropylene Fiber Concrete Mechanics Performance Test And Application On Bolt-shotcrete Support

Shotcrete has been widely used in coal mine roadway bolting and shotcreting support project, but the bolting form is restricted in high geostress and loose rock roadway. The shotcreting reinforcement mechanism shows, the deformation of ordinary concrete spray layer is limited, and it does not match with the deformation of the wallrock, soon after the spray layer is constructed, cracks appeared, then gradually losing the sealing process and supporting of surrounding rock. It's the main reason to cause bolting and shotcreting supports failure.Polypropylene fiber concrete as the roadway spray layer can effectively solve the problem of concrete crack. Its principle is mainly that the cement as cementitious material to grip the fiber in concrete, these fibers can use as subtle reinforcement, consume the energy of crack, improve toughness, reduce segregation and secrete water. Thus controlled the emergence and development of the crack in the cement, improve the crack-resistance of concrete. This paper is based on the mechanism of fiber enhancement. Through the 4 factors 3 levels orthogonal test, analyzed the influence factors of concrete compressive strength, splitting tensile strength and flexural strength such as fiber length, quantity of cement, sand percentage and cement water ratio, then got the optimal spray concrete ratio and trial length of fiber; Using the ratio to make the experiment on strength and impermeability of different fiber quantity and the suitable fiber quantity was determined. Use the FLAC3D software to analyze the polypropylene fiber concrete liner with the ratio, the numerical simulation calculation results show that the fiber concrete has strong non-deformability, is propitious to release the wall-rock pressure make full use of the bolt-shotcrete support system.The commercial tests were made based on the results in Tao Yuan coal mine, monitored the rebound quantity, wall-rock pressure, stress of the liner and roadway convergence under the condition of fiber concrete support. Monitoring results show that compared with ordinary concrete, the fiber concrete has strong stickiness, reduces the rebound quantity, increases thickness of sprayed concrete, has strong non-deformability, and the wall-rock stress well-distributed in the fiber concrete support. Research result is of great significance on the improved structure, promote rockbolt and shotcrete support technology development.