Research On Mechanism And Bearing Characters Of Y-section Pile Considering Abnormality Effect

Y-section pile is a new type of pile, whether the side friction is non-uniform distributed along its inverted arch arc, whether there is friction-weakening effect, how to determine the ultimate bearing capacity and tip resistance ration, it is necessary to research these issues. The studies include:(1) combine the cavity expansion theory to deduce the non-uniform distribution of skin friction and the ultimate tip resistance;(2) calculate skin friction additional stress oefficient and study its variation based on the non-uniform distribution model;(3) establish the theory of settlement and ultimate bearing capacity;(4)study the variation of skin friction, tip resistance and tip resistance ration of Y-section pile by numerical simulation, and compare the results with theoretical calculations. The innovation and perspectives are as follows:(1)Research the distribution traits of soil pressure and skin friction, calculate the ultimate tip resistance, using the function expression based on Y-shaped section parameters and soil parameters to establish the model of the pile skin friction and tip resistance and get the non-uniform distributed traits of skin friction, then study the variations of skin friction, tip resistance and tip resistance ration with the parameters of L、R、θ、s、δ. The skin friction is unevenly distributed, it is larger at the sharp corners while smaller at the midpoint of the arc.(2)Combine the function expression of non-uniform distribution model and mindlin formula to establish the calculation method of additional stress oefficient considering the cross-sectional shape and the non-uniform distribution traits by numerical integration and analyze the influences of the parameters L、R、θ、s、δ, then compare the conclusion with the uniform distribution solution and Geddes solution. Compared with the uniform distribution solution, the skin friction of the non-uniform distribution is less focused to the central axis, so the additional stress oefficient is smaller.(3) Calculate pile’s settlement under different loads according the skin friction additional stress oefficient based on non-uniform distribution model and tip resistance stress oefficient, predict ultimate bearing capacity of Y-section pile by the load-settlement rules, then compare the result with the method of ultimate skin friction and tip resistance and investigate influencing factors of the settlement and ultimate bearing capacity of Y-section pile.(4)Study the feature and variation of skin friction, tip resistance, settlement, Q-s curve and tip resistance ration of Y-section pile by finite element software, contradistinguish the result with theoretical calculations.