大粒径卵砾石地层多管同步注浆止水技术与试验研究

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

大粒径卵砾石地层影响半径大、渗透系数高、地下水补给量大,若采用降水方法进行地下水控制,将导致严重的水资源浪费;而该类地层可适用的帷幕止水方法种类较少,且不同止水方案对工期、造价影响较大。以北京地区某深基坑工程实例为分析条件,提出了多管同步注浆止水帷幕方案,通过开展工程场区内的现场注浆模型试验,系统研究了多管同步注浆的施工工艺、注浆材料及施工参数等关键技术指标。通过现场测定及室内分析,大粒径卵砾石地层袖阀管同步注浆扩散半径大于0. 5 m,注浆固结体渗透系数约5, 2×10^(-6) cm/s,可有效降低卵砾石地层的渗透性、极大程度减少基坑抽排水量,是一种可靠的深基坑工程止水辅助施工技术,可为类似地层条件下深基坑工程地下水控制设计及施工提供参考。

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.