Development And Numerical Simulation Of New Cement-based Anti-washout Grouting Materials

Cement grout is widely applied because of its inexpensiveness,ready sources,and high strength.However,its disadvantages such as poor injection ability,fragility of the solid,and poor ductility confine the practical application of cement grout.Chemical grout works well because of its good injection ability,its adjustable gel time,and its flexibility after solidification.Although chemical grout has special functions that cement grout does not have its application is restricted due to expensiveness and a lower solid strength.Given this situation and the previous studies,two new types of anti-washout cementitious grouts,named “KC-1” and “KC-2” respectively,have been developed for different geological conditions.Separate addition tests were performed to study the effects of certain accelerating agents and flocculating agents on the cement based grout comparatively.Based on the results of separate addition tests,two new formulations were proposed for further investigations.Both formulations involved three admixtures respectively.Grey relational analysis,coupled with Taguchi design of the combined addition experiment,was performed to determine the optimal admixture dosages for simultaneously achieving the desired yield stress and plastic viscosity of the cementitious grout.Multi-way ANOVA was employed to identify the insignificant factors which could be used to adjust the setting time and the compressive strength while not compromising the optimum rheological properties.The optimization algorithm was thus developed to achieve a faster set time,higher durability and stronger washout resistance for KC-1 but higher workability,sufficient washout resistance and nice setting speed for KC-2 according to their geotechnical applications.In addition,KC-1 requires a high-pressure grout pumping system.The washout resistance of the newly developed grouts was validated by anti-washout simulation experiments,and the anti-washout performance produced reasonable agreement with the rheological property of the grouting material.Finally,numerical simulation was employed to verify the diffusion mechanism of slurry under the hydrodynamic condition.The results suggests that the Flow 3D based model agreed closely with the observed experimental data,proving that the numerical simulation has the potential to predict and investigate the problem with regard to grouting application.