Interaction Analysis Of Multi-element Composite Foundation With Superstructure And Raft Footing

Multi-element composite foundation is an important breakthrough based on composite foundation theory in the period of from theory to practice with the ground treatment technology and it has sufficient theory evidence and good application prospect. With the continuous development of engineering technology, analysis to interaction of multi-element composite foundation and raft footing and superstructure has realistic necessity. Based on the research of predecessors, numerical analysis research to the interaction of multi-element composite foundation and raft footing and superstructure is preceded. Influence analysis of different pile dispose schemes to the interaction is the emphasis. Corresponding main work and achievements are as follows:①Multi-element composite foundation, raft footing and superstructure finite analysis theories are investigated, which include the corresponding constitutive model, computation element, thick plate analysis theory and so forth. Point to the influence of three kinds of unitary-element composite foundations that include rigid, soft, granular cases to the interaction of superstructure and footing with unitary-element composite foundation, investigation was carried out. The basis for the succedent research is prepared well.②Point to the influence of three kinds of two-element composite foundations that include granular-soft pile combination, granular-rigid pile combination, soft-rigid pile combination to the interaction of superstructure and footing with two-elements composite foundation, investigation was carried out. The pile disposal schemes use five modes including ’uniformly-spaced’, ’inner part strong and outer part weak’, ’outer part strong and inner part weak’, ’center part strong with inner and outer part weak’ and ’center part weak with inner and outer part strong’. The order of every pile disposal scheme for every single controlling target of raft settlements, raft and superstructure internal moment force from the best case to worst case is obtained. Comparisons show that every pile disposal scheme has its own shortcomings and advantages. Generally, pile disposal mode of ’center part weak with inner and outer part strong’ can not only reduce the raft settlements, but also decrease the internal force of superstructure and raft properly and it is a relatively optimal pile disposal mode. ③Point to the influence of three-element composite foundation combined wih granular-soft-rigid pile to the interaction of superstructure and footing with three-element composite foundation, investigation was carried out. The pile disposal schemes use seven modes including ’uniformly-spaced’, ’outer part strong and center part soft with inner part weak’, ’outer part strong and center part weak with inner part soft’, ’outer part soft and center part strong with inner part weak’, ’outer part soft and center part weak with inner part strong’, ’outer part weak and center part strong with inner part soft’ and ’outer part soft and center part soft with inner part strong’. The order of every pile disposal scheme for every single controlling target of raft settlements, raft and superstructure internal moment force from the best case to worst case is obtained. Comparisons show that every pile disposal scheme has its own shortcomings and advantages. Generally, pile disposal mode of ’outer part strong and center part weak with inner part soft’ can not only reduce the raft settlements, but also decrease the internal force of superstructure and raft properly and it is a relatively optimal pile disposal mode.④Select ’outer part strong and center part weak with inner part soft’ combination of granular-soft-rigid pile three-element composite foundation as the representative of multi-element composite foundation. Point to the influence of raft footing and superstructure to the interaction of superstructure and footing with multi-element composite foundation, investigation was carried out. Influence law of raft thickness, raft concrete strength, number of superstructure floors and superstructure floor height to the interaction of superstructure and raft foundation with multi-element composite foundation is investigated. Some useful conclusions are obtained.⑤Point to the influence of asymmetrical loads to the interaction of superstructure and footing with three-element composite foundation, three-element composite foundation wih the abolve seven granular-soft-rigid pile combination modes was choosed. In the center part heavy outside part weak loads distribution case, comparisons show that every pile disposal scheme has its own shortcomings and advantages. Generally, three pile disposal modes of ’outer part weak and center part soft with inner part strong’, ’outer part soft and center part weak with inner part strong’, ’uniformly-spaced’ can not only reduce the raft settlements, but also decrease the internal force of superstructure and raft properly and are the relatively optimal pile disposal modes. In the center part weak outside part heavy loads distribution case, generally, three pile disposal modes of ’uniformly-spaced’, ’outer part weak and center part strong with inner part soft’, ’outer part soft and center part strong with inner part weak’ are the relatively optimal pile disposal modes.⑥C++ language is used for devise of multi-element composition foundation, superstructure and raft footing interaction analysis program MSRIAP-2009. And the corresponding numerical computation analysis for the interaction of multilayer frame structure and raft footing with multi-element composition foundation can be carried out. The analysis results are available to corresponding science research and engineering practice.