Ttudy On Engineering Characteristics Of Long-short-pile Composite Foundation Under High-rise Buildings

With the continuous of foundation treatment technology progress, the appliance of composite foundation is more and more widely in civil engineering, a large number of the new foundation is applied to practical engineering projicts. Among them, that the long-short pile composite foundation as a relatively new form of composite foundation, it has been more and more attention of geotechnical engineering experts due to its remarkable economic and social benefits, but also facing a series of new problems. At present the mechanism about the long-short pile composite foundation, the theoretical research is not sufficient, and even there is no more perfect the design theory of the concept and calculation method. For beeter promotion and development of this new composite foundation, a systematic research on its engineering properties is very important. This artical mainly adopts thoretical analysis and engineering practice, and by means of analysis simulation of long-short pile composite foundation engineering properties are discussed and analyzed.Based on consulting a large amount of relevant documents, summarized the basic theory until now about the long-short pile composite foundation at domestic and abroad,development situation and its calculation method;Analysis of the long-short pile composite foundation and the length of pile composite foundation, concluded the two kinds of pile foundation are differenced on the structure and design concept; In the long-short pile composite foundation design and calculation,in bearing capacity calculation, compared the superposition method and the area weighted method step by step, two kinds of method to calculate the consistency. In terms of settlement, combined wih previous experience and achievement, deduces a new settlement calculation model, the result of calculation is more tally with the actual. Finally, this conclusion is validated by practical engineering case of theaccuracy and reliability, It is very important value for the long-short pile composite foundation theory research and application.This artical is based on foundation of the fundamental mode, analyzes the long-short composite foundation distortion characteristics with ABAQUS finite element software,by changing the load value, mattress layer thickness, mattress layer modulus, long pile module,long pile length, short pile modulus and short pile length, studied the long-short composite foundation engineering character and its mechanism, for its settlement and the load-bearing characteristics are discussed and analyzed, the main contents are as follows:(1)Generated three-dimensional model of long-short pile composite foundation by ABAQUS, then doing loading test, verify the feasibility of ABAQUS analysis long-short pile composite foundation. Get the change rule of stress disribution under foundation, settlement,axial stress of pile and stress ratio with the increase of load.(2)From the load parameters, mattress layer and pile analysis parameters of the the three major aspects, analyzed effects of paramenters on the long-short pile composite foundation settlement, axialstress of pile and pile-soil stress ratio, and according to the calculated results summarized the reasonable value range of parameters.