Study On Engineering Properties Of Composite Foundation Of Rigid-Flexible And Long-Short Piles

Firstly, the basic theories and the development of composite foundation are summarized in this paper, and the mechanism and the calculating theory for the rigid-flexible and long-short piles composite foundation are introduced and analyzed.Then, the author systematically analyzes the engineering characteristic of the composite foundation of rigid-flexible and long-short piles. The numerical analysis is presented by using ABAQUS programme and Drucker-Prager elastic-plastic model is included. The author calculates and analyzes the effects of some important parameters to the settlement and load percent ratio of this kind of composite foundation, such as the module and length of the piles, the module and thickness of cushion, and so on.The results of the numerical analysis indicate that:1. The settlement of the foundation occurs mainly in the region under the pile cap.2. At certain point under the pile the stress come to the maximum and it will move upwards along the pile with the load increasing.3. According to the horizontal displacement curves of the soil, the length of flexible pile can confine the displacement of the soil, so the settlement of the foundation will decrease.4. The major influence factors on load percent are the length of rigid pile and the thickness of cushion. The percent increases while the length increases until it reach a certain length, therefore the pile have an effective length. The load percent on the rigid pile will attain the maximum value without cushion. It is obvious that the cushion can diminish the stress concentration.5. Both the length of the rigid pile and the module and the thickness of the cushion have major effect on the settlement of the soil.Finally, the test data of Jingyuan project in Jiaojiang city is summarized. The results calculated by ABAQUS are in accord with the results of the test very well.