Research and application of cement-sodium silicate two-component synchronous grouting material in shield tunnel
At present,the application of cement-sodium silicate(C-S)two-component grouting materials in the field of synchronous grouting is increasing.However,in actual projects,especially in large-diameter shield tunnels,the problems of material performance regulation,pipe clogging,and tail sealing with dual slurry,holding the shield tail of C-S grout,and the corresponding control measures are seldom mentioned.By taking Beijing East Sixth Ring Road super-diameter shield tunnel project as the project background,this paper investigated the role of the base material and its influence on the physical and mechanical properties of C-S grout through orthogonal tests,and put forward a kind of C-S grouting ratio for shield tunnel in water-rich sand layer.Further,the fluidity,gelation characteristics and compressive strength of C-S grout injected from the pipeline were verified by the adaptability test,and the construction control measures and application effect of C-S synchronous grouting in actual projects were summarized based on engineering practice.The results show that:1)In C-S grout,the early gelation time is mainly affected by sodium silicate,the 28-day strength is mainly affected by cement,and the dosage of both is the most important factor in controlling the mechanical properties of C-S grout.2)Due to the fast-setting characteristics,the grouting fraction of C-S grout should be set to avoid grout in the shield tail gap to overcome gravity upward extrusion.Pipeline cleaning should be carried out after the completion of the synchronous grouting of each segment ring,bentonite grout should be used to replace C-S grout for shield tail blocking when the shield machine is shut down for a long period of time.3)In the application of the actual project,C-S grout can fix segment in about 4 h,so that the vertical deformation of the segment ring is between-10 mm and 10 mm.The ground settlement can also be stably controlled at-4.3 mm to 3.3 mm in about 280 h,which comprehensively improves the quality of the tunnel.The conclusions of the study provide a reference for the application and optimization of C-S grout in the field of synchronous grouting in shield tunnels.
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