The Horizontal Bearing Mechanism And Behavior Of Composite Foundation By Finite Element Analysis

With rapid development of national economy, the foundation establishment and its scale in our country become larger and larger, its difficult continuously increase.Civil engineering functionalization, three-dimensional urban construction, high speed of transportation, and peoples living condition improvement have become the characteristic of modern civil engineering. In the field of civil engineering, with the superstructure compare, a lot of uncertain factor of foundation, make the problem more complicated. More and more natural foundation can not satisfy the project requestment,as a result composite foundation development rapidly. The composite foundation technology can fairly make good use of foundation both the strengthen body and natural foundation to bear the building (structure) loads ,and its economic application relatively. However, in contrast with the wide use of the composite foundation, its theoretical research is very much lag behind, which seriously restrains the development and betterment. At present ,lots of research concentrate in the mechanism and behavior under vertical loads, less research on horizontal loads.In order to strengthen theoretical research on horizontal loads, this paper use the three-dimensional finite element methods to analysis the horizontal displacment and contact element between pile-top and cushion.In this paper, firstly, the basic theory of composite foundation is introduced,and describe the research and application of the rigid pile composite foundation,discussing the CFG pile composite foundation working mechanism and failure mode briefly. According to the experimental data and Technical Code for Ground Treatment of Buildings (JGJ 79-2002), use the Finite element method software ANSYS9.0 to establish 2D planar strain model ,through the analysis of this simiplified model,acquaint the operation mechanism of the procedure ,and the behavior of the structure. Then establishing the three-dimensional calculation model and to give out the difference of two kinds of establishing methods. Finialy, It based on enterprise integrated model to investigate that the effects of different affecting factors on the horizontal load behavior of the composite foundation , with which the distribution law of horizontal displacement along pile head,draws the following conclusions:1. When the other conditions were identical, horizontal displacement of pile head decrease with the increase of vertical load;2. When the other conditions were identical, horizontal displacement of pile head decrease with the increase of cushion thickness; 3. When the other conditions were identical, horizontal displacement of pile head decrease with the decrease of cushion compression modulus;4. When the other conditions were identical, horizontal displacement of pile head decrease with the increase of embedded foundation;5. When the other conditions were identical, horizontal displacement of pile head decrease with the increase of pile soil compression modulus;With the result of the numerical analysis, vertical load at proper level will enhance the horizontal load bearing capacity of composite foundation; Due to the effect of the cushion layer in the composite foundation , the horizontal load transferred to piles will be decreased ;the bigger embedded foundation will also decrease the displacement of pile head and the pile will be safer. These conclusions will play a role of guidance for engineering practice, and lay down a basis for further developing the theory for composite foundation.