摘要
针对非对称荷载下溶洞顶板极限承载力问题,引入抛物线形式的Hoek-Brown强度准则,并假定非对称荷载下溶洞顶板的冲切破坏体为轴对称旋转体。采用极限分析上限法建立了冲切破坏体的功能方程,利用变分原理和偏导求得了非对称荷载下溶洞顶板冲切破坏模式的极限承载力计算表达式。最后通过室内试验验证了理论方法的合理性,并分析了厚径比h/D、荷载位置偏移量e及岩体地质力学分类指标GSI对溶洞顶板极限承载力的影响。结果表明:(1)当e一定时,随着厚径比h/D的增加,顶板极限承载力大致呈线性增长,增大到一定值时,溶洞对顶板承载力无影响,顶板极限承载力趋向于完整基岩承载力;(2)当h一定时,随着荷载位置偏移量e的增大,溶洞顶板极限承载力呈非线性增长,增大到一定值时,溶洞对顶板承载力无影响,顶板极限承载力接近完整基岩承载力;(3)当h一定时,随着GSI的增大,顶板极限承载力增长的幅度逐渐变大。其中对于h为2D的溶洞顶板,且当GSI为44,e为0,0.25l,0.5l时,顶板的极限承载力分别为1.8,2.2,3.6 kN;当GSI为100时,相应的极限承载力分别为24,29,43 kN,近似为前者的12倍。因此GSI的选取对承载力的确定有重要意义,可为实际工程设计提供参考。
Aiming at the problem of the ultimate bearing capacity of karst roof under asymmetric load, the Hoek-Brown strength criterion in parabolic form is introduced, and the punching failure body of the karst roof under asymmetric load is assumed to be axisymmetric rotating body. Then, the functional equation of the punching failure body is established using the limit analysis upper bound method, and the expression of the ultimate bearing capacity of the punching failure mode of cave roof under asymmetric load is obtained by using the variational principle and the partial derivative. Finally, the rationality of the theoretical method is verified by laboratory test, and the influences of thickness-diameter ratio h/D, load position offset e and rock mass geomechanical classification indicator GSI on the ultimate bearing capacity of cave roof is analyzed. The result shows that(1) When e is constant, the ultimate bearing capacity of roof increases approximately linearly with the increase of thickness-to-diameter ratio h/D. When it increases to a certain value, the karst has no influence on the bearing capacity of roof, and the ultimate bearing capacity of roof tends to that of intact bed rock.(2) When h is constant, the ultimate bearing capacity of karst roof increases nonlinearly with the increase of the load position offset e. When it reaches a certain value,the bearing capacity of roof is not affected by karst cave, and the ultimate bearing capacity of roof is close to that of complete bedrock.(3) When h is fixed, the ultimate bearing capacity of roof increases gradually as the GSI increases. Wherein, for the karst roof whose h is 2D, and when GSI is 44, e is 0, 0.25l and 0.5l, the ultimate bearing capacity of the roof are 1.8, 2.2, 3.6 kN. When the GSI is 100, the corresponding ultimate bearing capacity is 24, 29, 43 kN respectively, which is approximately 12 times the former. Therefore, the selection of GSI has important significance for the determination of bearing capacity, which can provide a reference for practical engineering design.
作者
刘一新
雷勇
邓加政
刘泽宇
欧阳鹏博
LIU Yi-xin;LEI Yong;DENG Jia-zheng;LIU Ze-yu;OUYANG Peng-ho(Key Laboratory of Geotechnical Engineering for Stability Control and Health Monitoring of Hunan Province,Hunan University of Science and Technology,Xiangtan Hunan 411201,China;Guangzhou Zhongke Huada Engineering Technology Inspection Co.,Ltd.,Guangzhou Guangdong 510220,China)
出处
《公路交通科技》
CAS
CSCD
北大核心
2020年第4期104-110,共7页
Journal of Highway and Transportation Research and Development
基金
国家自然科学基金项目(51878270)。
关键词
隧道工程
极限承载力
极限分析上限法
岩溶顶板
冲切破坏
tunnel engineering
ultimate bearing capacity
limit analysis upper bound method
karst roof
punch failure
