大直径嵌岩桩桩端极限承载力计算方法  

Calculation methods for ultimate end bearing capacity of large diameter rock-socketed piles

作　　者：张琦[1,2] 刘军[1,2] 戴国亮[1,2] 龚维明[1,2] 

机构地区：[1]东南大学混凝土及预混凝土结构教育部重点实验室,南京210096 [2]东南大学工程学院,南京210096

出　　处：《东南大学学报（自然科学版）》2018年第1期118-124,共7页Journal of Southeast University：Natural Science Edition

基　　金：国家自然科学基金青年基金资助项目(41602300); 江苏省青年基金资助项目(BK20150618); 中国矿业大学深部岩土力学与地下工程国家重点实验室开放基金资助项目(SKLGDUEK1503); 贵州省交通厅科技资助项目(2015-122-051)

摘　　要：为更加准确获得大直径嵌岩桩桩端极限承载力,假定桩端岩体整体连续滑裂破坏、桩周岩体剪切破坏、桩周岩体微裂纹断裂破坏3种可能的极限状态,基于岩体二维、三维Hoek-Brown(H-B)破坏准则、岩体微裂纹Ⅰ-Ⅱ型复合判据,提出4种大直径嵌岩桩桩端岩体极限承载力的计算方法.引用现有实测数据对所提出的计算方法进行对比分析和验证,结果表明所提出的4种计算方法均比较接近实测值,尤其是基于Ⅰ-Ⅱ型复合判据的桩周岩体微裂纹断裂的桩端极限承载力计算结果与实测值最为接近.进一步研究了大直径嵌岩桩的尺寸效应,研究表明,桩端极限荷载与嵌岩深度及桩径密切相关,嵌岩桩桩端极限荷载随嵌固深度的增大而增大,而随桩径的增大而减小.4种计算方法中基于Ⅰ-Ⅱ型复合判据的桩周岩体微裂纹断裂计算方法与现场实测规律更加相符.To obtain the ultimate bearing capacity of the large diameter rock-socketed piles,three ultimate states of the rock mass on the pile tip are considered,w hich are the continuous slip failure on the pile tip,the shear failure surrounding the pile tip and the fracture of the micro-cracks surrounding the pile tip. Based on tw o-dimensional,three-dimensional Hoek-Brow n failure criteria and the micro-crack Ⅰ-Ⅱ composite criterion,four calculation methods for the ultimate bearing capacity of the pile end on the large diameter rock-socketed piles are proposed. Using the existed measured data,the proposed calculation methods are analyzed and verified. The results of the four proposed methods are close to the measured values,especially the result of the calculation method based on the Ⅰ-Ⅱcomposite criterion considering the fracture of the micro-cracks surrounding the pile tip. The size effect on the large diameter rock-socketed piles is further studied. The result show that the ultimate bearing load of the pile end is closely related to the rock-socketed depth and pile diameter,and the results show that the ultimate bearing load of the rock-socketed pile increases with the increasing of the rock-socketed depth and decreases with the increasing of the pile diameter. The results obtained by the calculation method based on the Ⅰ-Ⅱ composite criterion considering the fracture of the micro-cracks surrounding the pile tip are consistent with the observed results from the field among the four calculation methods.

关 键 词：嵌岩桩 桩端端承力 计算方法 破坏模式 复合判据 

分 类 号：TU47[建筑科学—结构工程]