[Objective]To solve the problems of"draught without slurry",poor groutability and slurry stability in the grouting process of completely weathered granite,a new composite grouting material is proposed in this paper to improve the anti-seepage and mechanical properties of completely weathered granite.[Methods]Through a series of laboratory experiments,it investigates the effects of different water-solid ratios,superfine bentonite,and superfine Portland cement content on the engineering properties of grouting materials.The formation mechanism of the slurry were studied,and the optimal formula of the cement slurry was determined.The experiment revealed the action mechanism of the two superfine materials on the fluidity,stability,and stone body strength of the grout.Finally,the castability and effectiveness of the grouting material were verified by a field test.[Results]The results show that the composite slurry with a water-solid ratio of 1.2,a content of superfine bentonite and superfine Portland ce-ment of 10％,and a content of ordinary Portland cement of 80％has good fluidity,stability,and resistance.The funnel viscosity was 35.5 s,the water separation rate was 2.4％,and the compressive strengths at 7 d and 28 d were both greater than 5 MPa.The compressive strength and the content of superfine bentonite in the composite ma-terial play a leading role in the properties of the slurry.The content of superfine bentonite and the morphology and distribution of its hydrated colloids determine the stability of the slurry,while an appropriate amount of superfine Portland cement increases the content of fine particles,making it easier for the cement to fill the gaps between the particles and improving the injectability of the slurry and the strength of the stone body.[Conclusion]The com-posite grouting material has excellent performance in the field test and good grouting performance.The wall formed after grouting meets the design requirements in terms of the anti-seepage effect and reinforcement performance.
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