考虑地应力作用的嵌岩桩基础岩体完整性系数评价

岩体完整性系数是桩基设计中评价岩体完整程度的重要指标之一。根据在建的济南恒大国际金融中心(总高518 m)嵌岩桩设计对岩体完整性评价的需求,在现场岩体纵波速度测试的基础上,开展了原位地应力(围压)条件下,桩端持力层深度岩块纵波速度测试,结果表明:强风化辉长岩(埋深69~80 m)的完整性系数为54.1%~58.8%,微风化辉长岩(埋深94~99 m)的完整性系数为77.2%~94.4%。随着风化程度的降低,地应力作用对岩体完整性系数的影响增强,考虑地应力作用下强风化地层的岩体完整性系数(均值)降低了2.1%,微风化地层的岩体完整性系数(均值)降低了5.2%。建议在超深嵌岩桩基础设计中,需考虑原位地应力对岩体完整性系数的影响。研究结果对嵌岩桩岩体完整性系数评价及超高层建筑地基勘察具有一定指导意义。

Rock mass integrity evaluation and application of rock-socketed pile foundation in Jinan Area

Rock mass integrity is one of the most important indicators for the evaluation of rock-socketed pile foundation. Based on the requirement and logging while drilling of Jinan HengdaInternational Financial Center which is being built, the compressive wave velocities of typical gabbro cores were measured in the laboratory with different confining pressures. After that the rock mass integrity were computed. Compared with the compressive wave velocities without confining pressure, the rock mass integrities of the cores with confining pressure were more suitable for reflecting the real situation. The result shows that the fracture development, which is influenced by different degree of weathering, in the rock is the major influence factor of rock mass integrity. The rock mass integrity of highly weathered gabbro in Jinan district, whose depth is 69-80m, is between 54.1% and 58.8%, while the weakly weathered gabbro, whose depth is 94-99m, is from 77.2% to 94.4%. The mean value of rock mass integrity with confining pressure of highly weathered gabbro decreases 2.1%, while the mean value of rock mass integrity with confining pressure of weakly weathered gabbro decreases 5.2%. It should be considered for the influence of rock mass integrity with confining pressure in the design of super deep project in the future. The result of this paper will be useful and instructive for the rock-socketed pile and foundation investigation of super highrise building.