礁灰岩嵌岩桩的模型试验

Model test on rock-socketed pile in reef limestone

援建马尔代夫的马累-机场岛跨海大桥项目作为我国"一带一路"的经济建设规划之一,桥梁桩基坐落于与我国南海珊瑚礁岩土体结构极为相似的珊瑚礁中。由于国内外开展珊瑚礁嵌岩桩的设计经验不足,故需要通过试验方法获取珊瑚礁嵌岩桩的承载特性和相关数据。对取自马累岛和机场岛桥基位置的礁灰岩岩芯开展室内桩基承载特性试验研究。测得礁灰岩的密度、相对密度、饱和单轴抗压强度、三轴剪切强度等基本物理力学指标,结合礁灰岩中嵌岩桩模型试验结果,获得模型桩承载力随桩端位移的变化规律。试验结果表明:桩岩界面先后经历弹性剪切、剪应力跌落和摩擦剪切3个阶段。在弹性剪切阶段,界面剪切变形以弹性变形为主,极限弹性位移η呈现出随弹性模量E增大而递减的趋势。在剪应力跌落阶段,应力软化急剧,并很快过渡到界面的摩擦剪切。通过试验发现,在低围压下,礁灰岩的残余侧摩阻力与饱和单轴抗压强度呈正相关关系。随着围压增大,残余侧摩阻力受围压影响较大。

As one of ＇the Belt and Road Initiative＇ economic development program, the Cross-sea Bridge in Male-Airport island was constructed by China. The foundation of the bridge was located in coral reef which was similar to the geotechnical structure in South China Sea. Due to lack of design experience of rock-socketed pile in coral reef in China and overseas, it is necessary to obtain the load-bearing characteristics and relevant data of rock-socketed pile in coral reef by appropriate test method. Indoor experimental study was conducted on mechanical properties of reef limestone cores that came from pile foundation of the bridge in Male-Airport island. Basic physical and mechanical parameters such as density, relative density, saturate uniaxial compressive strength and triaxial shear strength of the reef limestone were tested. Combining the consequence with the results from model rock-socketed pile test on the reef limestone, the variation law of the bearing capacity with the pile tip displacement was obtained. The investigation suggested that the interface of the pile and rock experienced elastic shear, shear stress drop and fiction shear stage. In the elastic shear stage, the shear deformation was mainly elastic deformation, and the ultimate elastic displacement decreased with the increase of the elastic modulus. In the stage of shear stress drop, the stress rapidly softened, and transformed to the fiction shear stage. In the test, the shaft resistance of reef limestone was positively correlated with the saturate uniaxial compressive strength under low confining pressure. Meanwhile, shaft resistance was greatly influenced by the confining pressure when confining pressure rose.