Analysis On The Properities Of The Long-short-pile Composite Foundation

With the continuous development of national economy and expanding scale of constructions, the ground treatment technology develops rapidly in our country. Many new types of composite foundations have been put into practice. The long-short-pile composite foundation is one of them. The long-short-pile composite foundation is a new concept, which is different from the incompact material pile composite foundation, the flexible pile composite foundation and the rigid pile composite foundation. It is composed with rigid long piles,short flexible piles and soil. They work together to bear capacity and deformation. In recent year, The long-short-pile composite foundation is used in the eastern coastal area of our country, and it has achieved good economic benefits and social benefits.From the application of long-short-pile composite foundation, it has good prospects, and more and more geotechnical scholars and engineers are concerned about it. It is believed that the long-short-pile composite foundation treatment is one of the preferred methods in ground treatment. Reasonable model and analysis methods are used to reveal the bearing mechanism and deformation characteristic of the long-short-pile composite foundation, so that the mature theory and the improved technology of ground treatment are popularized widely. At the same time, it is very significative that reasonable design parameters are chosed to optimize the design of composite foundation.The following aspects are studied in this paper:Firstly, This paper reviews design concept and application of the long-short-pile composite foundation. Secondly, the methods to analyze the bearing capacity and the settlement of the long-short-pile composite foundation have been summarized. Finally, based on the unique advantages of numerical method, the model of the long-short-pile composite foundation is established, and some factors affecting the pile-soil stress,the pile-soil stress ratio,the load percent ratio and the settlement of the long-short-pile composite foundation such as the the thickness and module of cushion the length,module and diameter of long (short) pile and the distance between piles have been calculated and analysed by using finite element method. Some forms of pile plane layout of composite foundation have been simulated, and the author analyses the results such as the pile stress, the pressure changes of the basement and the settlement. The results can be referred for optimization design in practice.