礁灰岩嵌岩桩的端承特性试验研究

Experimental research on end bearing characteristics of rock-socketed pile in reef limestone

为服务中马友谊大桥项目中的桩基础设计,探究礁灰岩嵌岩桩的桩端承载特性,利用在拟建桥基处钻孔取得的礁灰岩样,开展室内物理力学性质试验和端承桩模型试验研究,得到桩端礁灰岩样在三向受压状态下的强度和破坏规律。试验表明,桩端应力较无侧限压缩试验提高明显,桩端应力的增长趋势受岩样强度和结构类型影响较大。在不同结构类型的礁灰岩中,桩端应力随桩顶位移的变化曲线呈现不同的增长趋势。考虑到实际桩径和模型试验的比尺对试验的影响,试验依据《建筑基桩检测技术规范》(JGJ106—2014)确定出不同结构类型礁灰岩的单桩竖向抗压极限承载力,并结合现场试桩试验结果进行强度折减,得到不同结构类型礁灰岩的极端阻力标准值的设计参考值。

In order to serve the pile foundation designs in China-Maldives Friendship Bridge construction project, and investigate the end bearing characteristics of rock-socketed pile in coral reef limestone, indoor mechanical tests and end bearing pile model tests were carried out on the reef limestone cores drilling from the bridge foundation position. By these means,the strength and failure law of reef limestone samples under three direction compression in the pile end are obtained. Experiment results show that the pile end stress are obviously higher than the uniaxial compression strength,and greatly influenced by specimen structure and strength. In different structure specimens,the pile end stress curve are in different growth trend with pile top displacement. In the processing of test results, we determined the vertical compressive ultimate bearing capacity of single pile in different structure specimens according to the technical code for testing of building foundation piles(JGJ106—2014). Considering the influence of diameter scale between actual pile and model test,the design reference of ultimate end bearing value in different structure types of reef limestone are determined after reduction associate with in-situ pile test result.