基于上限定理确定岩溶区桩端极限承载力及其下伏溶洞顶板安全厚度  

Determination of ultimate bearing capacity of pile tip and safety thickness of cave roofs under pile tip in karst area based on upper bound theorem

作　　者：贺建清[1] 喻畅英 肖兰[1] 高文华[1] 

机构地区：[1]湖南科技大学岩土工程稳定控制与健康监测省重点实验室,湖南湘潭411201

出　　处：《自然灾害学报》2017年第2期47-52,共6页Journal of Natural Disasters

基　　金：国家自然科学基金资助项目(41272324);岩土工程稳定控制与健康监测省重点实验室开放基金项目(PKLHD201309)~~

摘　　要：嵌岩桩因单桩承载力高、沉降量小等优点而在工程中,尤其是高层建筑及大型构筑物中得到了广泛的应用。岩溶区嵌岩桩桩端岩层极易发生冲切破坏。引入用小而非零拉伸截断改进的M-C强度准则描述岩体的破坏特性,确定破坏面上单位面积的能量耗损率;从极限分析上限定理出发,构建了岩楔体平移破坏机构;根据桩端荷载和冲切圆台自重所做的外功率与冲切圆台破坏锥面的能量耗损率相等的条件,建立了虚功率方程,并由此得到了岩溶区桩端极限承载力的上限解及其下伏溶洞顶板安全厚度的计算公式。工程实例分析表明,该方法具有一定的可靠性,可为岩溶区类似建筑桩基的设计和施工提供参考。Rock socketed pile, due to its advantages as higher beanng capacity, smaller settlement and so on, has been widely used in engineering, especially high-rise buildings and large structures. Rock stratum at pile tip is prone to punching failure in Karst area. In this article, the modified M-C stress criterion with a small but not zero tension cut-off was introduced to describe the failure characteristics of rock masses. An expression was derived with the aforementioned M-C stress criterion for the energy dissipation rate per unit area. Based on the upper bound the- orem for the limit analysis of plasticity mechanics, the translational failure mechanism of rock wedge was put for- ward. The virtual power equation was deduced in terms of the rate of work done by load of pile tip and rock weight of punching cone equaling to the rate of energy dissipation along the sliding surface of punching cone, with which the upper bound solution of the ultimate bearing capacity of pile tip as well as the calculation formula of the safety thickness of cave roofs under pile tip were obtained in karst area. The engineering case analysis shows that the a- bove formulas have certain reliability, which can provide reference for the design and construction of similar building pile foundation in karst area.

关 键 词：嵌岩桩 冲切破坏 M-C强度准则 极限分析 极限承载力 安全厚度 

分 类 号：P315.93[天文地球—地震学] X93[天文地球—固体地球物理学]