Study On Mechanical Properties Of Fractured Rock Mass Filled With Cement Slurry

Filling cement slurry has important theoretical and engineering significance for strengthening fractured rock and maintaining the stability of fractured surrounding rock.Especially,the excellent characteristics of ultra-fine cement,such as high durability and high strength,have obvious effect on controlling fractured surrounding rock.In this paper,a series of shear mechanics tests of fissured rock filled with cement slurry with different particle sizes were carried out by a self-designed direct shear test system.The macro-fracture evolution law and micro-structure distribution characteristics of fissured rock filled with cement slurry were analyzed by acoustic emission monitoring and scanning electron microscopy.The influence of different particle sizes on the rheological parameters of grout is studied through the fluidity test of fissured rock filled with cement slurry,so as to realize the feasibility of the flow of cement slurry in fissured rock mass.The results are as follows:(1)Fissure samples of red sandstone with moderate roughness were prepared.The direct shear test of filling different types of cement mortar red sandstone fissure rocks was carried out by self-designed direct shear test system.The acoustic emission signals during shear process were monitored by acoustic emission monitoring system.The research results show that the shear stress-shear displacement curves of filling three types of cement mortar fissure rocks are different.The line shape was basically the same,and there was no obvious peak value.Under the same normal stress,the shear strength,shear stiffness,cohesion and other mechanical parameters of rock filled with ultra-fine cement fissures have been significantly improved.(2)Through real-time observation of fracture process of filling cement slurry fissure rock by high-definition CCD camera,the macro-fracture evolution law and failure mode of filling cement slurry fissure rock with different particle sizes are discussed.It is found that the interface between rock wall and slurry stones begins to separate first in the process of shear failure.With the further increase of shear deformation,the cement stones are gradually sheared.The micro-structure characteristics of cement stone body and magma-rock interface with different particle sizes were studied by scanning electron microscopy.The results show that the number of holes and defects in the superfine cement in the transitional zone between the stone body and the interface are significantly reduced,the structure is more compact and the integrity of the structure is better than that in the ordinary water.(3)The feasibility study on the flow of fissure rock filled with cement slurry is carried out.The results show that the apparent viscosity of superfine cement slurry I and II is generally higher than that of ordinary cement slurry,and the apparent viscosity of three kinds of cement slurry decreases first and then increases with the increase of water reducer content.Based on Bingham model,the variation of rheological parameters such as yield stress and plastic viscosity of cement paste with water reducer content was analyzed.