帷幕注浆在富水地层桩基施工中的应用

研究目的:帷幕注浆具有施工机具不受空间的限制、无大量返浆和废液需要处理以及对地下水和环境无污染等优点,对不同地层均能取得土体强度增加、渗透系数明显减小的工程效果,并产生良好的护壁作用。采用帷幕注浆可解决在渗透系数大、承压水头高的地层中进行特大桥桩基施工中面临成孔困难的问题,本文进一步探讨了该工艺在西南地区某长江大桥施工中的应用经验。研究方法:结合某长江大桥桩基施工的工程实例,论述了帷幕注浆的设计要点、施工工艺,并且介绍了判定帷幕注浆止水效果的原位测试方法,对测试结果进行了深入的分析。研究结果:在正常的压力状态下,地层的综合渗透系数在10-5cm／s数量级;在水压力大于0．3 Mpa情况下帷幕可能会出现水力劈裂现象,导致渗透系数增大。研究结论:采用帷幕注浆止水效果明显,保证了桩基的顺利施工。

APPLICATION OF CURTAIN GROUTING IN THE PILES CONSTRUCTION OF WATERY STRATA

Research purpose: This method of Curtain Grouting had the advantages of selection for construction equipment without limit of time and space, little flush fluid of grout-recycling in the hole and wastewater that are not particularly treated and no pollution to underwater and environment. And then the strengths of all kinds of strata soil treated by this method had a great increment, the permeability of which decreases greatly. And strata soil treated could protect borehole walls and cores. The problem, which was difficulty of forming boreholes in the piles construction of watery strata with high peermeability and high confined water head, could be solved by application of curtain grouting and further discussed the application experience of this technology in southwest area of Yangtze River Bridge. Research method: As the practical engineering of Yangze River Bridge for example, this paper discussed the key points, construction technology and test method of water proof in situ. Research result: The result of test in situ revealed that the permeability of all kinds of strata soil was about 10-5 cm/s in an average water pressured state, but maybe increase so that strata soil maybe hydrosplitted in the water pressure that was more than 0.3 MPa. Research conclusion: The conclusion demonstrated that the curtain grouting technology could prevent water very well when holes were dug.