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Mechanism and application of controllable grouting in loose strata before shield tunneling |
ZHANG Cong1,YANG Junsheng1,YE Xintian1,ZHANG Zhibo2,ZHANG Guijin3,ZHANG Yi1 |
(1. School of Civil Engineering,Central South University,Changsha,Hunan 410075,China;2. China Railway 14th Bureau Group Tunnel Engineering Co.,Ltd.,Jinan,Shandong 250000,China;3. School of Hydraulic Engineering,Changsha University
of Science and Technology,Changsha,Hunan 410114,China) |
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Abstract Treatment to the loose strata,such as the excavation(drilling) and backfilling,the pressure grouting and the jet grouting reinforcement etc,should be undertaken to ensure the safety of shield tunneling. A double-controlled grouting method was proposed with two kinds of controllable slurries(controllable filling and controllable cement paste slurry) based on the controllable characteristics of traditional grouting process through sleeve valve tube. The proposed method is very handy to operate in practice and easy to lift the pipe. The range of reinforcement is controllable and the appropriate strength of reinforced solid can be achieved. The diffusion equation of the controllable grout in soil strata was derived and a formula for the slurry control in grouting process was derived according to the operating principle of double-controlled grouting. The method was applied to the shield tunneling in loose strata of a river-crossing project successfully. The results of the study and application show that the continuity and integrity of stratum is improved significantly after the grouting treatment. The drilling process of inspection hole is carried out smoothly in reinforced area,the core samples have the structural integrity and the compressive strength and permeability coefficient of the samples meet the design requirements of reinforced solids after 28 days. To achieve the optimum effect of grouting,a single injection height should be controlled within 15 m,the distance of radial diffusion should be less than 25% of the distance between the arrayed holes,the plastic strength of the controllable filling should be controlled in 0.3 MPa to 0.5 MPa.
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[1] |
刘汉龙,赵明华. 地基处理研究进展[J]. 土木工程学报,2016,49(1):96-115.(LIU Hanlong,ZHAO Minghua. Review of ground improvement technical and its application in China[J]. China Civil Engineering Journal,2016,49(1):96-115.(in Chinese))
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