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考虑地层空间变异性的岩溶区基础可靠度分析
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Reliability Analysis of Footings Lying on Karst Area Considering Spatially Variability of Stratum
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    摘要:

    基于随机场理论和 Karhunen-Loeve 展开构造随机场以模拟具有空间变异性的地 层,并结合有限元极限分析法和蒙特卡洛模拟对含溶洞地层上的基础开展可靠度分析 .本文 重点是通过大量数值模拟进行全面参数分析,探究地层中溶洞特征(如溶洞埋深、溶洞水平偏 移距离)以及土体空间变异性参数(如土体相关长度、土体变异系数)对基础极限承载力以及 失效概率的影响;进而结合可视化溶洞-基础体系破坏模式深入揭示岩溶区基础失效概率变 化机理;最后将有限元极限分析结果与已有研究进行对比,验证了数值模型的准确性及研究 结论的可靠性 .结果表明体系破坏线发散度越大,则基础在受荷破坏时可能发展出的破坏路 径越多,从而导致失效概率提高;此外,下伏溶洞距基础越远或土体空间变异性越强则基础失 效概率越高,且失效概率将随所选取安全系数的增加而大幅降低 .在前期设计中若采用本文 方法进行可靠度分析,为确保安全性,安全系数应尽量大于2并采用下限理论进行分析.

    Abstract:

    This study simulates the soils with spatial variability by random field theory and Karhunen-Loeve ex? pansion. Reliability analysis of strip footing lying on karst area is carried out based on finite element limit analysis and Monte Carlo simulation. The emphasis of this study is performing the parametric analysis through finite element modeling,in order to explore the effect of karst cave parameters(including depth and horizontal offset distance of karst caves)and spatial variability parameters(including correlation length and coefficient of variation)on the ulti? mate bearing capacity and failure probability of footings. Then,combined with the visualization of failure patterns of cave-footing system,the variation mechanism of footing failure probability is revealed. Finally,the finite element analysis results are compared with the existing research results to verify the accuracy of the numerical model and the reliability of the research conclusions. The results indicate that the higher the disperse degree of failure curve is,the more failure paths may develop under external loads,which leads to a higher failure probability of the footing. Fur? thermore,the footing failure probability increases with the increase of distance between the karst cave and the footing. The higher spatially variability of soils also leads to a higher failure probability of the footing. And the failure probability decreases significantly with the increasing factor of safety. If the method proposed in this paper is used for reliability analysis in the advanced design,the safety factor should be larger than 2 as far as possible and the lower limit theory should be used for analysis,in order to guarantee the safety.

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吴高桥 ,聂建国.考虑地层空间变异性的岩溶区基础可靠度分析[J].湖南大学学报:自然科学版,2022,49(7):45~53

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  • 在线发布日期: 2022-08-18
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