Study on Pressing Pipe Pile into Complicated Foundation

Abstract

It was relatively difficult to press pipe pile statically into complicated ground. With mud of large proportion protecting holes, pushing piles into Pre-cited hole in sandy ground was introduced in this assay, and the requirement of engineering demands were fully met after a strict on-site test, which could be a worthy reference for the similar projects. Introduction The piles of pre-stress high-strength concrete have been widely used in many constructions in recent years. With the development of basic theory and engineering practice, the applied scope of pushing pre-stress high-strength concrete pile in ground gradually expanded, and there have been some successful cases in thin sand layer [1] or gravel layer [2]. The standard penetration test and static cone penetration test in dense sand layer showed that it was not a easy thing to press pre-stress high-strength concrete pile in complicated foundation. Pre-guide-hole technology in pile position is an effective measure to solve the difficult problem of jacking pile in sand [2, 3], and the constructing process of pre-guide hole and jacking pile would easily cause collapse in sand ground which made it extremely difficult to sink pile in soil. Combining with an engineering example, slurry pre-guide-hole construction techniques would be introduced to jack pre-stress high-strength concrete pile in sand ground in this assay. General Engineering Geology The construction is a high-rise residential of on the ground 28 layers and underground 1 layer, located in northeast district in Zhengzhou. The foundation is buried deep below ground 6 m, and the underground water level is 6 ~ 7 m under the surface . The project is located in the alluvial plain of the Yellow River, and the main soil from top to bottom are distributed as follows: First layer: miscellaneous soil, formed of construction waste and domestic waste, with an average thickness of 0.8m; Second layer: silty clay, locally inter bedded with silty layer, with an average thickness of 4.1m; Third layer: fine sand, medium dense to dense, saturated, with an average thickness of 25.2m; Fourth layer: hard plastic silty soil, clipped in several fine sand layers, with an average thickness of 50m.Considering the foundation form of high-rise residential in Zhengzhou area, and on the basis of safe, applicable, economic, durable principles, pre-stress high-strength concrete pile, filling pile and composite foundation of CFG pile were compared to find a better foundation form. Finally, the 15m PHC400-AB100-C80 pile was chosen as the foundation of high building. Pile square layout with a spacing of 1.5m*1.5m, and the bearing capacity characteristic value is 1200kN. A total of 1897 piles was used in the foundation. Difficulties During Constructing According to the construction sequence, construction technical difficulties were mainly as follows: