一种填方路堤反压护道断面设计的解析方法研究
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摘要
针对软弱地基上的高速公路填方路堤稳定性问题,利用整体圆弧法稳定性分析原理,推导了同时考虑滑动面上黏聚力c和内摩擦角?联合作用的平衡方程;并将滑面上内摩擦角?在滑面切向方向上的作用等效为黏聚力作用,提出在此条件下的等效黏聚力概念;进而利用平衡方程和等效黏聚力讨论了合理反压护道宽度和高度的确定方法。以某高速公路反压护道工程为背景,进行了护道断面尺寸的设计计算和分析,并将安全系数和滑体特征与规范推荐方法进行了对比分析。结果表明:相对只考虑黏聚力的计算结果,综合考虑黏聚力c和内摩擦角?联合作用的分析方法更接近大部分软弱地基内摩擦角非零的工程实际条件,且在获得相同安全系数时具有更优的断面尺寸(节约用地和土方量);该方法与规范推荐方法计算的安全系数有紧密的联系,其值取1.05时与规范容许值较为吻合;该方法能避免设计中依靠经验反复试算确定护道尺寸的盲目性,可减少设计工作量。
To investigate the stability of the expressway embankment on soft ground, the whole arc method is used to deduce a limit equilibrium equation with coupling variables of internal friction angle ? and cohesion c.The effect of internal friction angle on the tangential direction of slip surface is then assumed equivalent to cohesion effect, and the concept of equivalent cohesion is proposed. Based on the limit equilibrium equation and the equivalent cohesion, a procedure to calculate the optimal section size of loading berm is developed. The proposed procedure is used to design the section size of the loading berm and to determine the safety factor for a expressway embankment, and the calculated results are compared with the method from the code. The results show that because the combining effect of internal friction angle ? and cohesion c is considered, the proposed procedure has a greater advantage in acquiring the optimal section size of loading berm than the method recommended by the code, in which only cohesion is considered. The safety factor calculated by the proposed method is 1.05, which agrees well with the results obtained with the method from the code. The proposed method can avoid the shortcomings of traditional methods that require experience in determining the size of berm.
To investigate the stability of the expressway embankment on soft ground, the whole arc method is used to deduce a limit equilibrium equation with coupling variables of internal friction angle ? and cohesion c.The effect of internal friction angle on the tangential direction of slip surface is then assumed equivalent to cohesion effect, and the concept of equivalent cohesion is proposed. Based on the limit equilibrium equation and the equivalent cohesion, a procedure to calculate the optimal section size of loading berm is developed. The proposed procedure is used to design the section size of the loading berm and to determine the safety factor for a expressway embankment, and the calculated results are compared with the method from the code. The results show that because the combining effect of internal friction angle ? and cohesion c is considered, the proposed procedure has a greater advantage in acquiring the optimal section size of loading berm than the method recommended by the code, in which only cohesion is considered. The safety factor calculated by the proposed method is 1.05, which agrees well with the results obtained with the method from the code. The proposed method can avoid the shortcomings of traditional methods that require experience in determining the size of berm.
引文
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[15]中国建筑科学研究院.GB 50330-2013建筑边坡技术规范[S].北京:中国建筑工程出版社,2013.
[2]朱梅生.软土地区路堤合理断面之选择[J].土木工程学报,1964,11(2):48-60.ZHU Mei-sheng.Selection of reasonable cross-section of embankment in soft soil region[J].China Civil Engineering Journal,1964,11(2):48-60.
[3]王晓谋,袁怀宇.高等级公路软土地基路堤设计与施工技术[M].北京:人民交通出版社,2001.
[4]陈金锋,宋二祥.西南山区机场高填方边坡反压护道优化设计[J].工程力学,2012,29(6):85-97.CHEN Jin-feng,SONG Er-xiang.Optimized design of loading berm for highfill slope of airport in mountainous area of Southwest China[J].Engineering Mechanics,2012,29(6):85-97.
[5]张玉成,杨光华,胡海英,等.在软土地基上有反压护道路堤及堤坝的稳定计算[J].岩土力学,2007,28(10):844-848.ZHANG Yu-cheng,YANG Guang-hua,HU Hai-ying,et al.Stability study of embankment or dam with back berm on soft soil foundation[J].Rock and Soil Mechanics,2007,28(10):844-848.
[6]李建国,王珣.路基承载力与路堤稳定性及沉降关系研究[J].铁道工程学报,2014,188(5):21-27.LI Jian-guo,WANG Xun.Research on the relationship among roadbed bearing capacity,embankment stability and settlement[J].Journal of Railway Engineering Society,2014,188(5):21-27.
[7]ROY D,SINGH R.Mechanically stabilized earth wall failure at two soft and sensitive soil sites[J].Journal of Performance of Constructed Facilities,2008,22(6):373-380.
[8]曹海莹,窦远明.上硬下软型双层路基应力扩散特征及工程应用[J].公路交通科技,2012,29(2):29-34.CAO Hai-ying,DOU Yuan-ming.Characteristics of dry crust’s stress dispersion in two-layer roadbed and its engineering application[J].Journal of Highway and Transportation Research and Development,2012,29(2):29-34.
[9]宋二祥.土工结构安全系数的有限元计算[J].岩土工程学报,1997,19(2):1-7.SONG Er-xiang.Finite element analysis of safety factor for soil structures[J].Chinese Journal of Geotechnical Engineering,1997,19(2):1-7.
[10]张鲁渝,郑颖人,赵尚毅,等.有限元强度折减系数法计算土坡稳定安全系数的精度研究[J].水利学报,2003,34(1):21-27.ZHANG Lu-yu,ZHENG Ying-ren,ZHAO Shang-yi,et al.The feasibility study of strength-reduction method with FEM for calculating safety factors of soil slope stability[J].Journal of Hydraulic Engineering,2003,34(1):21-27.
[11]蒋鑫,邱延峻,魏永幸.基于强度折减法的斜坡软弱地基填方工程特性分析[J].岩土工程学报,2007,29(4):622-627.JIANG Xin,QIU Yan-jun,WEI Yong-xing.Engineering behavior of subgrade embankments on sloped weak ground based on strength reduction FEM[J].Chinese Journal of Geotechnical Engineering,2007,29(4):622-627.
[12]DUNCAN J M.State of the art:Limit equilibrium and finite element analysis of slopes[J].Journal of Geotechnical Engineering,1996,122(7):577-596.
[13]四川蜀通岩土工程公司.遂资眉(洪雅)高速公路遂宁至资阳段A合同段K9+500路基沉降工程地质勘察报告[R].成都:四川蜀通岩土工程公司,2012.
[14]中华人民共和国交通运输部.JTG/TD31-02-2013公路软土地基路堤设计与施工技术细则[S].北京:人民交通出版社,2013.
[15]中国建筑科学研究院.GB 50330-2013建筑边坡技术规范[S].北京:中国建筑工程出版社,2013.