The Study Of Failure Model On Limit Equilibrium Of Gravel Pile Composite Foundation

As a common method in dealing with weak soil foundation, gravel pilecomposite foundation could be achieved by transferring the nature foundation intothe composite foundation composed of gravel pile and the surrounding soil body.The operating state and failure model of gravel pile composite foundation, to alarge degree, is based on the engineering properties of weak soil site. Therefore, itis of vital theoretical significance and practical application value to investigate thefailure model of composite foundation of gravel pile.In the present study, mechanisms in the bearing of gravel pile compositefoundation was analyzed on the basis of previous report and several project cases.Furthermore, common methods in calculating the bearing capacity of gravel pilecomposite foundation were compared. On this basis, novel method of capacitycalculation for gravel pile composite foundation was proposed by the introductionof rational assumption and failure model of pile body limit equilibrium constructedaccording to the plastic zone scope in the controlled foundation.A large number of engineering experience evidenced that gravel pilecomposite foundation was commonly exhibited as bulging shear failure, and itsbearing capacity depended on the hoop force of the ambient soil body. It wasassumed that the composite foundation was subject to complete solidification priorto the construction completion, and pile and soil matrix were both homogeneouselastomer; the weight of pile and soil body were omitted; in view of t he regulatingeffect of the cushion, the base pressures of pile cap and the surrounding soil wereassumed to be homogeneous, respectively, meanwhile the strength of pile and soilwere not affected by the cushion material, neglecting the thickness of cushion;when it was loaded, the pile body was firstly subject to shear failure, then thesurrounding soil yielded due to the bulging effect of pile cap, and gave rise toultimate limit state of bearing capacity for the composite foundation; insideshearing strength of the pile was zero within the scope of pile cap bulging, so thereinforced layer of the composite foundation could be calculated as an integralwhole. To this end, the bearing capacity of foundation for gravel pile wasdetermined according to the development scope of limit equilibrium area in thecontrolled foundation, to deduce to formula for calculating its bearing capacity. Theengineering example indicates that the method proposed in the study is simple andfeasible.