Construction Technology Of Underwater Bored Pile In Complex Karst Cave Geology Areas

At present, with the vigorous development of the national economy, bored pile is the first choice for bridge foundation, such as highway, railway, and municipal, etc.,and its design theory and construction technology have gradually been improved.However, due to the construction of bored piles has a high degree of concealment, the process control is often more complex than the superstructure, more prone to quality hazards. The cause of the completed pile quality control is many, and the cave treatment is a very important work. If mishandled, quality accident will be produced;major losses to the national property probable are caused.For a long time, in the treatment of bridge pile foundation drilling in the cave area, the most of measures was used including the filling with rubble and clay, setting up steel retaining tube, grouting, or pouring into low grade concrete, etc.. However,due to the regional differences, and the complexity of the geology, if using only a of the processing method, the complex karst cave geology can’t be effectively resolved in the construction, especially for the karst geological conditions in the upper layer is silt clay, the lower limestone. This bored pile through karst caves in this case used the steel protecting tube and filling with rubble and clay to plug the cave, in order to reach stable wall of the hole, to guarantee the good quality.In this paper, using the bridge cross Jiujiang Saicheng Lake in Jiangxi province as engineering example, the underwater bored pile foundation construction technology through karst cave area were studied, and to put forward a complete set of construction quality control system. The difficulty of bored pile construction in Karst area of lies in the destruction of the continuity of the engineering geological conditions, compared with the pile through the normal conditions, its technology is more complex, and more types of diseases, such as slurry leakage, leakage of concrete, sticking, drill burying and partial hole etc. Combining with the constructionpractice in this paper, the disposal techniques of underwater bored grouting pile encounter cave are summarized, and to put forward processing methods suitable for different types of cave, as well as measures to deal with the universal problems in the construction.The technology research about underwater bored filling pile in karst areas, can better guidance for similar project construction, and speed up the construction process,to ensure the safety and to reduce quality accidents, improving the social effect and economic benefits.