Research on Technique and Experiment of Multi-pipe Synchronous Grouting and Water-blocking in Large Particle Gravel Strata

The large influence radius and the high permeability coefficient are the characteristics of large particle gravel strata which holds abundant groundwater.Using the method of precipitation to control the groundwater will cause serious waste of water resources.The sealing curtain techniques are fewly applicable to the large particle gravel strata.In addition,different water-blocking schemes have great influence on the construction period and cost.By taking an example of deep foundation pit in Beijing as the analysis condition,this paper puts forward a scheme with multi-pipe synchronous grouting and water-blocking for deep foundation pits.By carrying out grouting model tests in the engineering site,some key technical indexes,such as the construction technology,grouting material and construction parameters,are systematically studied of multi-pipe synchronous grouting.By field measurement and laboratory analysis,this paper makes the following conclusions:When the grouting diffusion radius is greater than 0.5 m and the permeability coefficient of grout is greater than 5.2×10^—6 cm/s,by using the method of synchronous sleeve valve tube grouting in large particle gravel strata,the permeability of gravel stratum will be decreased;The drainage of the foundation pit will be greatly reduced simultaneously.So this reliable water-blocking technique can provide reference for the groundwater control design and construction of similar foundation pit engineering in deep foundation pit.