Experiment on Reinforcement of Jointed Rock Mass by Carbon Fiber Cement-based Composite Material
【Abstract】In order to investigate the reinforcement effect, mechanism, and the optimum carbon fiber content of carbon fiber cement-based composite material for jointed rock mass, taking 0, 0.25%, 0.50%, 0.75%, 1.00% as five different kinds of carbon fiber content into consideration, we conducted the direct shear tests on the rock specimens before and after reinforcement by dint of the ultrafine cement, fly ash, mineral powder, silica fume, and other repair materials. The results showed that the shear stress-shear displacement curves of the jointed rock specimens before and after reinforcement were obviously changed, which were transformed from the absence of peak intensity to peak intensity curves. There were significant strain-softening stages and residual strength stages. With the carbon fiber content increased from 0 to 1.00%, the peak shear strength and residual shear strength of jointed rock specimens under five kinds of normal stress cases increased by 13.0%–54.1% and 0.61%–44.7%, respectively. The shear stiffness increased from 32.4% to 216.8%. The cohesion and friction angle of the shear strength parameters increased by 3.4%–20.4% and 127.3%–266.5%, respectively. In comparison, when the carbon fiber content was 0.75%, the comprehensive enhancement effect of the shear resistance after reinforcement was most obvious. According to the morphological features of joints and shear failure characteristics after reinforcement, it is found that the cement composite material had a good filling and cementation effect on the joint surfaces. When the carbon fibers were incorporated into the cement-based composite material, on the one hand, it is similar to “reinforcement” material, and the strength and integrity of the slurry can be further enhanced on the basis of the pure cement slurry to limit the development of micro-cracks during the shear process of the joint surface. On the other hand, carbon fiber provided a good “anchorage” effect on the sheared slurry, which can further increase the cementing property of the slurry and the joint surfaces to significantly increase the shear resistance of the slurry itself and the cementation surface. Hence, after reinforcement, the comprehensive shear resistance of the jointed rock mass can be improved significantly.
【Keywords】 road engineering; reinforcement mechanism; direct shear test; jointed rock mass; carbon fiber;
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