The Diffusion Law Of Cross Fracture Grouting Based On The Time-dependent Behavior Of Viscosity Of Grout

With the continuous development of the economy, the demand for energy development and transportation construction is increasing as well, so the underground engineering construction projects are increasing such as the tunnel engineering projects and mining engineering projects. As a result, the geological disasters are more frequent and serious in the process of these underground engineering construction projects such as water outburst and mud outburst. As one of the effective means to control the geological disasters, grouting has the function of sealing the fracture in the surrounding rock, improving the mechanical properties and permeability of the injection medium. However, the relevant theoretical research cannot meet the needs of grouting engineering due to the diffusion of slurry in the fracture network is complex. In this paper, the physicochemical property of cement grout and cement-based fast curing grout, and the diffusion law of two kinds of grout in the cross fracture model are studied by laboratory test, numerical simulation, engineering verification. The main results are as follows:(1) The viscosity of cement-water glass and cement-water glass with retarder was measured by laboratory test. The conclusion that the gel process of cement-based fast curing grout such as cement-water glass can be divided into 3 stages, as mixing stage, initial setting stage and curing stage, and the gel time becomes shorter when the cement-water ratio and mixing volume ratio are smaller was proposed. The effect of phosphate retarder on cement-water glass slurry was studied at the same time. The results showed that the phosphate retarder make the cement-water glass slurry keep in initial setting stage and maintain low viscosity for a long time after mixing. Finally, the test data were fitted, and the viscosity time-varying equations of the 2 kinds of slurry in different ratio were obtained, which provided a reference for the numerical simulation.(2)The two dimensional plane cross fracture model was established to simulate the diffusion process of cement grout and cement-based fast curing grout in the cross fracture model. The simulation showed that the diffusion shape of grout under the same grouting rate in the static water ambient is the same in the model. For cement grout, due to the viscosity of the grout is basically unchanged, the grouting pressure rising rate is slow, and the pressure field is effected obviously by the branch fracture. For cement-based fast curing grout, due to the viscosity of the grout is changing rapidly with time, the grouting pressure rising rate is fast, and the pressure field is effected inconspicuously by the branch fracture. In dynamic water ambient, the inlet position of grout, the flow velocity of groundwater and the grouting rate have influence on the diffusion process of cement grout. When the inlet position of grout is in the main fracture, and the grouting rate is greater than the groundwater flow rate, the influence of the groundwater on the dilution of the grout is smaller.(3)The three dimensional cross fracture model was established to simulate the diffusion process of cement grout and cement-based fast curing grout in the cross fracture model. The simulation showed that in the static water ambient, for cement grout, due to the viscosity of the grout is basically unchanged, the diffusion shape of grout in main fracture and branch fracture is regular, the distribution of pressure field is uniform, and the diffusion shape and the distribution of pressure field are effected obviously by branch fracture. For cement-based fast curing grout, due to the viscosity of the grout is changing rapidly with time, the diffusion shape of grout in main fracture and branch fracture is irregular, the distribution of pressure field is uneven, and the diffusion shape and the distribution of pressure field are effected inconspicuously by branch fracture. In dynamic water ambient, the inlet position and flow velocity of groundwater have influence on the diffusion process of cement grout. When the inlet position of ground water is in the main fracture, and the grouting rate is greater than the groundwater flow rate, the diffusion of grout is stable, and the filling effect for the model is good.(4)For controlling the geological disaster in water gushing section of tunnel in Hunan, the appropriate grout and proportion were chosen by test on the basis of the above research results. The area of fracture with rich water was found on the basis of results of the exploration report. Beside the traditional curtain grouting design, the key hole grouting design was increased for the area of fracture with rich water. The tunnel gushing was controlled effectively, and the method provided a reference for other similar projects.