顺向缓倾岩层临坡地基复合破坏模式与极限承载力计算  

Compound Failure Mode and Ultimate Bearing Capacity Calculation for Footing near Horizontal Consequent Slope

作　　者：胡惠华 王宏祥 张鹏 曹文贵[4] 刘榕 刘海波 HU Hui-hua;WANG Hong-xiang;ZHANG Peng;CAO Wen-gui;LIU Rong;LIU Hai-bo(Hunan Provincial Communications Planning,Survey and Design Institute,Changsha 410200,Hunan,China;Hunan Provincial Key Laboratory of Highway Construction and Maintenance Technology in Southern China,Changsha 410200,Hunan,China;Hunan Communications Research Institute Co.Ltd.,Changsha 410015,Hunan,China;School of Civil Engineering,Hunan University,Changsha 410082,Hunan,China;Hunan Construction Investment Group Co.Ltd.,Changsha 410004,Hunan,China)

机构地区：[1]湖南省交通规划勘察设计院有限公司,湖南长沙410200 [2]中南公路建设及养护技术湖南省重点实验室,湖南长沙410200 [3]湖南省交通科学研究院有限公司,湖南长沙410015 [4]湖南大学土木工程学院,湖南长沙410082 [5]湖南建设投资集团有限责任公司,湖南长沙410004

出　　处：《中国公路学报》2023年第6期49-57,共9页China Journal of Highway and Transport

基　　金：国家自然科学基金项目(52078206,51879104);湖南省交通科技进步与创新计划项目(201003,202119,202120)。

摘　　要：顺向缓倾岩层临坡地基的破坏模式及极限承载力,与层面抗剪性能及产状与组合关系密切相关。迄今为止,众多学者基于临坡地基极限承载力的滑移线法对这一问题开展了研究,这些方法可以考虑层面特征与组合关系的影响,相比其他方法具有明显优势。然而这些研究大多都假设主动朗肯区底部与优势结构面直接相接,忽略普朗特尔过渡区的范围,这在一些情况下会出现计算结果偏大等问题。针对上述问题,基于滑移线严格解,考虑地基中客观存在的普朗特尔过渡区,采用应力间断面静力分析的力矩平衡法,建立了顺向缓倾岩层临坡地基极限承载力试算方法。采用该方法对不同倾角的顺向缓倾岩层破坏模式进行了分类:当岩层倾角小于最小临界值βmin,时,岩体发生“自锁”,为均质破坏模式;当岩层倾角大于最大临界值(βmin,βmax)时,发生顺层滑动破坏;当岩层倾角位于区间βmax时,发生复合破坏模式。最后将该模型应用于洞庭溪沅水特大桥中。结果表明:忽略过渡区范围的双平面破坏模式在该工程中应用时,计算结果偏大;所提方法计算结果最小,符合潘家铮“极小值”原理,计算结果更准确。所提方法考虑了岩基中层面特征组合与客观存在的普朗特尔过渡区的影响,计算确定了顺向缓倾岩层临坡地基不同破坏模式下岩层倾角临界值,并通过试算确定复合破坏模式中抵抗力最小破坏面,是一种准确确定临坡地基承载力的新方法。The failure mode and ultimate bearing capacity of a footing near a horizontal consequent slope are closely related to the shear resistance of corresponding layers.Accordingly,many scholars have investigated the ultimate bearing capacity of slope footings based on the slip line theory.Current methods consider the influence of layer characteristics;however,most theoretical studies assume that the active Rankine zone intersects with the dominant structural plane,ignoring the Prandtl transition zone range.Therefore,in some cases,new problems may arise,i.e.,the calculation result can be too large.Regarding this,based on the strict solution of the slip line theory,the Prandtl transition zone,and the moment balance method of stress discontinuities,a trial calculation method for the ultimate bearing capacity of a footing near a horizontal consequent slope was established,and the failure modes of the clockwise gently inclined strata under different dip angles were classified in this study.When the dip angle of rock stratum is less than critical valueβmin,“self-locking”of rock mass occurs,which is a homogeneous failure mode;When the dip angle of rock stratum is greater than critical valueβmax,bedding sliding failure occurs;When the dip angle of rock stratum is in the interval(βmin,βmax),composite failure mode occurs.Finally,the model was applied to Yuanshui bridge and the results show that for the biplane failure mode,because the transition zone was ignored,shear failure of the rock mass occurred parallel to the structural plane near the slope,so the calculation result was large and the project is deemed dangerous.The calculation result of the proposed method is the smallest and conforms to Pan's minimum principle;and is therefore the most accurate considering this project.In summary,this method takes into account the unfavorable conditions of the slope and structural surface combined.In addition,it can be used to calculate and determine the critical value of the dip angle of the rock layer under different failure

关 键 词：道路工程 层状岩体 滑移线理论 极限承载力 临坡地基 力矩平衡法 

分 类 号：U416.1[交通运输工程—道路与铁道工程]