Study On Character Of Pile-Soil Cooperative Work In The Composite Pile Foundation

With the development of economics in our country and the mass construction of infrastructure, how to use limited resource in such a large number of projects is very important for a developing country such as China. The composite pile foundation technology is more economic than other traditional method because it can reduce the number of pile greatly. For the great perspective of composite pile foundation, it becomes research highlight in Geotechnical Engineering. After decades of research by many experts, there is no perfect design theories and calculate methods yet. Further research on the character of pile-soil cooperative work in composite pile foundation is still needed.Because many facts need to be considered in the effect of pile-raft-soil working together, the composite pile foundation is hard to be implemented lacking of information. In this essay, the author analyze the working character of foundation with different position, thickness of soil beside pile, pile spacing, elastic modulus of pile, deformation modulus of soil and raft depth, by building 3-dimensional, non-linear FEA models with ABAQUS. It can be a reference for the design of composite pile foundation in real project, to make the design accord with real condition more closely.Make a set of field measurements for one project in Shaoxing city, including the stress of piles and soil and the settlement of the buildings. The results show that composite pile foundation can meet requirement of the buildings in using, reach the expected effect, and low the price.When loads on the pile top increasing, soil will enter the plastic stage. So it's important to choose an appropriate constitutive model. According to the geological conditions, this paper makes FEA calculations when the soil is adopted Drucker-Prager model, Mohr-Coulomb model and cap model respectively. It can be seen that the calculation results agree well with the real measurement results .At present, the existent design theories of composite pile foundation didn't forma valid method to confirm the number of piles still. Based on the project in Shaoxing city, the author analyze the characters of laying different number piles in composite pile foundation and designing by general pile foundation theory by FEA method. Through comparing the results, some conclusions are gained.