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现浇X形桩是通过等截面周边扩大原理,将圆形截面的正拱变为反拱而成的。作为一种新型的异型截面桩,目前对其极限承载力的计算仍采用规范中建议的经验公式。结合南京桥北污水处理厂地基处理工程的现场静载荷试验,应用有限元软件ABAQUS,建立刚性荷载下现浇X形混凝土桩复合地基的模型,模拟不同桩身模量、桩周土模量、桩长、褥垫层厚度和模量等参数下现浇X形混凝土桩复合地基的荷载-沉降关系,从而得出复合地基的极限承载力。结果表明,现浇X形桩单桩复合地基极限承载力比等截面面积的圆形桩单桩复合地基增大20%以上,X形桩4桩梅花形复合地基极限承载力比等截面面积的圆形桩大12.35%。极限承载力随桩身模量、褥垫层模量、桩周土体模量或者桩长的增大而增大,而且在众多影响因素中桩周土体模量对复合地基极限承载力的影响最为明显。
Cast-in-place X-shaped pile is expanded by the principle of equal section around the arch, the arch of the circular cross-section becomes inverted arches. As a new type of profiled section piles, the ultimate bearing capacity is still calculated using the empirical formula recommended in the specification. Based on the site static load test of foundation treatment project in Nanjing Qiaobei WWTP, the finite element software ABAQUS was used to establish the model of cast-in-situ X-shaped concrete pile composite foundation under rigid load. The simulation results of different pile moduli, , The thickness and modulus of cushion under load-settlement of X-shaped concrete pile composite foundation load-settlement relationship, so as to obtain the ultimate bearing capacity of composite foundation. The results show that the ultimate bearing capacity of cast-in-situ X-shaped pile composite foundation is larger than that of circular pile single pile composite foundation with equal cross-sectional area by more than 20%, and the ultimate bearing capacity of X-shaped piles of four plum-shaped composite foundation is larger than the equivalent cross- Circular pile big 12.35%. The ultimate bearing capacity increases with the increase of pile body modulus, cushion modulus, soil bulk modulus or pile length, and the influence of soil bulk modulus on the ultimate bearing capacity of composite foundation The impact is most obvious.