抗剪强度分项系数的标准差反馈标定法
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摘要
基于可靠度理论的分项系数极限状态设计方法是当今岩土工程设计的一个趋势,分项系数的标定是确定设计参数的关键。岩土材料强度分项系数需反映材料参数的变异性,现有理论方法如安全系数校核法、一次二阶矩校核法、验算点校核法等理论标定方法,没有明确说明分项系数如何降低参数不确定性的影响,理论基础有待进一步完善。因此,提出岩土材料强度分项系数的标准差反馈标定法,该方法在目标可靠度的基础上,通过观察均值的调整对标准差调整的抵消作用,确定材料强度分项系数,由此确定的分项系数能充分反映强度参数的离散性。通过算例对该标定方法的实现进行了说明,并与验算点校核法进行了对比分析,指出标准差反馈标定法比验算点校核法更加合理。
Limit state design method based on reliability theory is a trend of modern geotechnical design. Calibration of the partial factors is a key to determine the design strength parameters. Although there are safety factor calibration methods, first order second moment method and designed points method to calibrate the partial factor theoretically, the mechanism of how the partial factors reflect the variance of the geotechnical materials is still unknown. The standard deviation feedback calibration method is then proposed to solve this problem. The core concept of this method is to adjust the mean value of the strength parameters to offset the influence of the standard deviation adjustment. A case study is given to illustrate the method. A comparison between this method and the design points method is taken out to see their different effects on the design strength parameters. The results show that the standard deviation feedback calibration method is more reasonable and the design points method will lead to a conservative design which would raise the budget ultimately.
Limit state design method based on reliability theory is a trend of modern geotechnical design. Calibration of the partial factors is a key to determine the design strength parameters. Although there are safety factor calibration methods, first order second moment method and designed points method to calibrate the partial factor theoretically, the mechanism of how the partial factors reflect the variance of the geotechnical materials is still unknown. The standard deviation feedback calibration method is then proposed to solve this problem. The core concept of this method is to adjust the mean value of the strength parameters to offset the influence of the standard deviation adjustment. A case study is given to illustrate the method. A comparison between this method and the design points method is taken out to see their different effects on the design strength parameters. The results show that the standard deviation feedback calibration method is more reasonable and the design points method will lead to a conservative design which would raise the budget ultimately.
引文
[1]陈立宏,王玉杰,陈祖煜,等.国外岩土工程极限状态设计方法的进展[C]//水利水电工程风险分析及可靠度设计技术进展.北京:中国水利水电出版社,2010:290-313.CHEN Li-hong,WANG Yu-jie,CHEN Zu-yu,et al.Progress of limit state design method in geotechnical engineering abroad[C]//Proceedings of the Symposium on Risk Analysis and Reliability Based Design for Water Resources and Hydropower Projects.Beijing:China Water Power Press,2010:290-313.
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[9]LOW B K,TANGW H.Efficient reliability evaluation using spreadsheet[J].Journal of Engineering Mechanics,1997,123(7):749-752.
[10]KULHAWY F H.Improving geotechnical uncertainty evaluation in reliability-based design[M]//Engineering Geology for Society and Territory.New York:Springer International Publishing,2015:343-346.
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[12]HOEK E.Practical rock engineering[EB/OL].https://www.rocscience.com/learning/hoek-s-corner/books,2016-01-10.
[2]GULVANESSIAN H,CALGARO J A,HOLICKYM.Eurocode—Basis of structural design[J].Civil Engineering,1990,144(6):8-13.
[3]BAECHER G B,CHRISTIAN J T.Reliability and statistics in geotechnical engineering[M].Chichester:John Wiley&Sons,Inc.,2003.
[4]陈文,陈立宏,孙平.岩土材料性能分项系数的标定[C]//水利水电工程风险分析及可靠度设计技术进展.北京:中国水利水电出版社,2010:314-335.CHEN Wen,CHEN Li-hong,SUN Ping.Calibration of partial factors of shear strength parameters of geotechnical materials[C]//Proceedings of the Symposium on Risk Analysis and Reliability Based Design for Water Resources and Hydropower Projects.Beijing:China Water Power Press,2010:314-335.
[5]陈祖煜,陈立宏,王玉杰,等.滑坡和建筑物抗滑稳定分析中的可靠度分析和分项系数设计方法[C]//水利水电工程风险分析及可靠度设计技术进展,北京:中国水利水电出版社,2010:27-39.CHEN Zu-yu,CHEN Li-hong,WANG Yu-jie,et al.Reliability analysis and partial factor design methods for slope stability[C]//Proceedings of the Symposium on Risk Analysis and Reliability Based Design for Water Resources and Hydropower Projects.Beijing:China Water Power Press,2010:27-39.
[6]中国电力企业联合会.GB 50199-94水利水电工程结构可靠度设计统一标准[S].北京:中国计划出版社,1994.China Electricity Council.GB50199-94 Unified design standard for reliability of hydraulic engineering structures[S].Beijing:China Planning Press,1994.
[7]FENTON G A.GRIFFITHS D V.Risk assessment in geotechnical engineering[M].New Jersey:John Wiley&Sons,Inc.,2008.
[8]吴振君,王水林,汤华,等.边坡可靠度分析的一种新的优化求解方法[J].岩土力学,2010,31(3):713-718.WU Zhen-jun,WANG Shui-lin,TANG Hua,et al.A new optimization approach for slope reliability analysis[J].Rock and Soil Mechanics,2010,31(3):713-718.
[9]LOW B K,TANGW H.Efficient reliability evaluation using spreadsheet[J].Journal of Engineering Mechanics,1997,123(7):749-752.
[10]KULHAWY F H.Improving geotechnical uncertainty evaluation in reliability-based design[M]//Engineering Geology for Society and Territory.New York:Springer International Publishing,2015:343-346.
[11]ZHANG Chuan-qing,ZHOU Hui,FENG Xia-ting,et al.A new interpretation for the polyaxial strength effect of rock[J].International Journal of Rock Mechanics and Mining Sciences,2010,47:496-501.
[12]HOEK E.Practical rock engineering[EB/OL].https://www.rocscience.com/learning/hoek-s-corner/books,2016-01-10.