素混凝土劲性水泥土复合桩承载机理分析

Analysis of load-bearing mechanism of composite foundation of plain concrete reinforced cement-soil mixing piles

在软基中先施打半刚性水泥土类桩(M桩),水泥未硬凝时再施打劲性桩,形成素混凝土劲性水泥土复合桩(MC桩)。结合工程实例,根据现场静载试验、应力监测及ABAQUS有限元计算结果,研究了素混凝土劲性水泥土复合桩的受力性状,分析总结了素混凝土劲性复合桩的承载机理。通过与常规劲性桩的比较表明:(1)素混凝土劲性水泥土复合桩呈现复合地基性状;(2)素混凝土桩身应力集中显著,沿深度急剧减小,至桩端接近为"0",通过劲芯传递到侧壁和桩端的水泥土体中,增大了荷载作用于水泥土体的面积,使复合桩全长范围内的侧阻力和端阻力得到充分发挥;(3)素混凝土桩芯比常规劲性桩更能与水泥土协调匹配,不会刺入水泥土外芯的底端。

Plain concrete reinforced cement-soil mixing pile （MC pile） is a new kind of composite pile, which is made of semirigid cement-soil mixing pile （M pile） and rigid plain concrete pile （C pile）. The diameter of M pile is 500-700 mm; the diameter of C pile is 220-280 mm; and C pile constructs in the center of M pile before it congeals. This composite pile can exert the carrying capacity of soil, improve load pipeline and depth, control the advance extent by adjusting diameter, intensity of concrete, and so on; so it has been widely used along river and sea in Jiangsu Province. The pile＇s working property and load-beating mechanism are analyzed based on the plate loading test, stress test, and ABAQUS software. Compared to general reinforced mixing pile, MC pile works as a kind of composite foundation. Stress centralizes C pile and rapidly diminishes along with depth; and the stress in the end of pile is close to zero. MC pile exerts the carrying capacity of soil around the pile, because C pile can transfer load to cement-soil mixing pile. MC pile doesn＇t penetrate into cement-soil mixing pile like general reinforced mixing pile; for the capability of C pile is more close to cement-soil＇s.