管桩水泥土复合桩荷载传递机制试验研究

Experimental study of load transfer mechanism of composite pile of jet-mixing cement and PHC pile

为研究管桩水泥土复合桩荷载传递机制,结合工程实例,对其进行现场载荷试验及桩身光纤光栅应力测试.测量了桩身轴力、侧摩阻力及桩端阻力,分析了不同荷载下桩的荷载传递特性,比较该桩型区别于一般管桩的抗力特点.研究表明：管桩是竖向荷载的主要承担者,复合桩工作特性与刚性单桩相似;复合桩表现出摩擦桩的工作特性,桩端阻力只占桩顶荷载的8.2％ ～14.8％;复合桩荷载传递具有双层模式,桩顶荷载由管桩传递到水泥土桩再传递到桩间土并扩散到桩端持力层;水泥粉喷桩的施工及高强预应力混凝土（PHC）管桩的压入改善了桩周和桩端土体的物理力学性质及应力场分布,从而有效地提高了复合桩的承载力.

To study the load transfer mechanism of composite pile of jet-mixing cement and prestessed high-intensity concrete pile （CPCP） , static load and fiber bragg grating stress test were conducted on con- struetion site. Firstly, the axial force, the side friction resistance and the tip resistance of the piles were measured. Then, the load transfer mechanism at different load levels were analyzed and the resistance characteristics between normal pipe pile and CPCP were compared. Results showed that pipe pile carried the majority of vertical load in CPCP and cement pile characteristics was similar to that of rigidity pile, CPCP performed like friction pile, in which the pile end carried about 8.2% to 14. 8% of the total load. The load transfer of CPCP presents double-layer mode： load transfers from pipe pile to cement pile. then to surrounding soil, and finally spreaded to the bearing layer. Cement-soil pile and the PHC pile improved the physical mechanical property and stress distribution of surrounding and underlying soil of piles, thus enhancing the bearing capacity of composite pile.