With the development of ground treatment technique,rigid pile composite-foundation has been widely used in the ground improvement of high-rise building with raft foundation.Yet,for rigid pile composite-foundation ,the bearing capability and failure mechanism of the group pile composite-foundation under different load level,and the difference between single pile composite-foundation and group pile composite-foundation is still a worthy research problem at the present time. Large-scale model tests were carried to investegate the bearing behaviour and failure mechanism of rigid pile composite foundation with unequal pile spacing under the raft foundation.the interaction between pile and soil is discussed based on the test results.The distribution of stress of pile top and soil among pile,the settlement under different load level,load carriedby pile and soil with the variation of load level are studied,and the difference between the bearing capacity determined by group pile or single pile composite foundation load test and that determined by empirical formula was analysised.Finally,the level of safety,failure pattern and the development of failure of rigid pile composite foundation were studied and some suggestions were given.
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