| With the development of China's economy,the demand for railway construction in Karst areas is increasing.There are a lot of problems in the grouting reinforcement technology of Karst Foundation.The effect of Karst grouting has a direct impact on the service performance of the subgrade.On the basis of economic interests,improving the quality of the project has become a difficult problem in the design of Karst subgrade.At present,the conventional cement and sodium silicate cement are usually used in the grouting of Karst Subgrade.However,it is difficult to achieve the purpose of sealing cracks by use of conventional cement in the area where the crack is strong development,which results in the loss and waste of slurry,and the pollution of ground water,thus affecting and destroying the environment.Sodium silicate cement double liquid slurry is consolidated too fast,poor liquidity,and it is easy to cause grouting pipe blockage and other issues.Basing on the grouting test section of the Karst foundation in Qian Zhang Chang railway,this paper studied a new grouting slurry to meet construction demand.The influence parameters of slurry diffusion are studied by numerical analysis.Through the field experiment,the performance of slurry and grouting effect are evaluated.The main work and achievements of this paper are as follows:1.By collecting literature data,the paper summarizes the grouting technology,grouting slurry,grouting theory,slurry performance control,grounting model test,numerical analysis method,and the application of grouting in civil engineering,and puts forward the research content,method and technical route.2.The controllable slurry was proposed,and the controllability of the slurry flow was realized through the indoor experiment.In this paper,the effects of two kinds of external accelerators,two kinds of water retaining agents and one kind of water reducing agent on the initial setting,water loss rate and fluidity of cement slurry were studied.And the water cement ratio,additive and the mix proportion were optimized.Finally,the new slurry proportioning scheme were determined to meet the construction requirements.In the scheme,the grouting slurry have advantage of the short initial setting,the less water loss rate and the proper liquidity.A new type of composite slurry mixing ratio is developed.3.In this paper,the theoretical model of single fracture Newton grout is established.And the numerical analysis results of FLUENT software are verified by theoretical model.The influence of the crack opening,the radius of the grouting hole,the inlet pressure of the crack and the performance of the slurry(Based on Newton fluid and Bingham fluid)on the diffusion law of the slurry were studied by means of numerical analysis.The model of inclined crack grouting is established,and the influence of dip angle on diffusion radius is discussed.Some suggestions are put forward for the optimization design of grouting parameters.4.Field experiments were carried out to study the application of controllable slurry.The engineering application research on the practicability and applicability of the controlled slurry are achieved,and the expected control objectives are achieved.Finally,the grouting effect is evaluated by means of Geophysical prospecting and drilling. |
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