The Application Research Of High Pressure Jet Grouting Pile In Expressway Soft Foundation

High pressure jet grouting pile technology has been introduced into China for more than forty years since 1970s. At that time, this technology was mainly used in consolidation of soft-soil foundation,it was applied in impermeable dam after 1980s.At present, it has bee n spreaded over the country, and applied in large-scale projects such as the Xuan-Da expressway and Jing-Qin expressway. The technology has remarkable characters of safety, better suitability on soil, lower noises, high pile shaft strength, controllable consolidation figure, aboundant material, lower price and so on; so it is widely applied in consolidation of building foundation, deep foundation pit excavation and retaining, stability of slope, impermeable dam, etc.Soft loess foundation of Yin-Zhong expressway mainly distributes in the ditch spot which expressway acrosses the mountainous area, the distributed scope and basal surface is relation with the river erosion degree. Water content of soft loess in this area is high, W=24.5~35.1%,W≥WL,natural void ratio e0=0.68~1.31, the compressibility is big, the intensity is low. The degree of saturation is big, Sr=81.7%. IL=1.10,mostly assumes soft plastic to flow plastic, the engineering geology nature is bad. After the analysis and computation, the ground biggest subsidence quantity is 815.5mm, the bearing capacity of the foundation is about 70~100kPa. The soil filling depth of this soft foundation generally is 3~7.95m, the bearing capacity of the foundation should above 150~200kPa, the subsidence quantity should be smaller than 300mm, the stable safety factor should be bigger than above 1.1.Obviously this soft loess foundation cannot satisfy the request of the highway engineering, also because the depth of fill is bigger, the soil body and the ground are unstable, can produce skids. The basic principle of FEM and analysis software used in the paper are introduced, the construction procedure of Yin-zhong expressway is simulated,the stress, the strain and displacement characteristic are analyzed . Simultaneously established the model which had broken pile and the pile spacing changed .according the contrast results studied the influence of the flaw pile to the ground reinforcement .Taking Yin-Zhong expressway subgrade treatment for an example, This paper designs and construct High pressure sprinkling grouting composite foundation. Analysis the question which met in the construction process .Through the research of the article, the author advances personal opinions and suggestion on reasonably selecting parameters of devise, which has been proved by engineering data.