Research On The Mechanism Performance Of The Vertical Bearing Behavior Of The Long-short Pile-raft Foundation

Piled raft foundation is a widely used configuration of pile cluster, many domesticand foreign scholars had spent lots of time and energy on the researches. During thedesign of piled-raft foundation we always face the problem that more than onesupporting courses are available. If the lower supporting course is seleeted as thebearing stratum of pile foundation, the bearing capacity and settlement requirements areall will be meted but this will waste much money and bring larger constructiondiffieulty;if the upper supporting course is selected as the bearing stratum of pilefoundation, the settlement requirement is unsatisfied.Some researchers have proposed anew type of foundation named long and short piles-raft foundation,at present,thisfoundation has some application in practical engineering,but it is still a lack oftheoretical research,so the system theoretical research need to be done before a largenumber of engineering applications. According to the current study of piled raftfoundation and research results in the field at home,this paper makes in-depth researchon the property of long and short piles-raft foundation by large-scale finite elementanalysis software ABAQUS. The major work of this paper is focused on several aspectsas follows:1. Subject proposed and review the appliciation and development of the pilefoundation, pile group foundation and long and short piles foundation.2. Summarize the property and calculation methods of vertical loaded pile(including single pile and pile group), and describes the raft theory and pile-soilinteraction analysis method.3. Inruoduce the basic principles of the finite element method, and compare twocommonly used soil elastoplastic constitutive model (M-C model and D-P model), andanalysis how to achieve the pile-soil interaction in ABAQUS.4. On the basis of a three-dimensional model of the long and short-raft foundation,by altering long pile length, short pile length, shallow bearing stratum elastic modulus,deep bearing stratum elastic modulus, pile spacing, raft thickness and etc,analyze theinfluence of the average vertical displacement of top pile and maximum displacemnet,axial force and pile-soil load sharing ratio.5. Analyze an engineering example by ABAQUS and compared with the measuredvalues; analyze the main factors of the long and short-raft foundation by dimensional analysis; summarizes the design ideas.