基于PFC2D的土体缓冲落石冲击能力研究
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摘要
常用的拦石墙、棚洞等落石防护措施均需布置土体来缓冲落石造成的冲击力,其缓冲能力在进行防护措施结构设计时应合理考虑。颗粒流程序PFC2D(Two-dimensional Particle Flow Code)可有效模拟落石冲击土体和结构的动态过程,用来分析不考虑土体缓冲效应下的落石冲击力,结果与瑞士算法基本一致,略大于日本算法。进一步地,取不同厚度的素填土、粉质黏土和砂质粉土3种缓冲土层,分析不同坠落高度条件下落石经过土体缓冲后对结构的冲击力,发现土体的缓冲能力与土层厚度、缓冲能力与坠落高度均大致呈指数函数关系;坠落高度对缓冲能力的影响基本不随缓冲土体选材改变而变化;同样厚度条件下粉质黏土缓冲能力最大,素填土次之,砂质粉土最小。研究成果表明实际工程中缓冲土层厚度宜设定为2～3 m。
In the design of rockfall protection structure, the cushioning capacity of soils on stone cutoff wall or shed-tunnel against rockfall's impact force should be taken into consideration properly. PFC2 D could simulate the dynamic process of rockfall impacting on the soil and structure effectively. The calculated result of rockfall's impact force by PFC2 D with no consideration of soil's cushioning capacity is consistent with that by Swedish algorithm(proposed by Dr. Vincent Labiouse) and slightly larger than that by Japanese algorithm(proposed by Japanese Road Association). Furthermore, the impact forces of rockfall from different heights on structure with soil cushions—plain filling soil, silty clay, and sandy silty soil each of different thicknesses—are analyzed. The cushioning capacity of soil is in exponential function relation with soil cushion's thickness and rockfall's height; while the influence of falling height on cushioning capacity does not change with the change of soil material. Given the same soil thickness, the cushion capacity of silty clay is the largest, followed by that of plain filling soil and sandy silty soil in sequence. From an economic point of view, the thickness of soil cushion is recommended to be within 2-3 meters in engineering practice.
In the design of rockfall protection structure, the cushioning capacity of soils on stone cutoff wall or shed-tunnel against rockfall's impact force should be taken into consideration properly. PFC2 D could simulate the dynamic process of rockfall impacting on the soil and structure effectively. The calculated result of rockfall's impact force by PFC2 D with no consideration of soil's cushioning capacity is consistent with that by Swedish algorithm(proposed by Dr. Vincent Labiouse) and slightly larger than that by Japanese algorithm(proposed by Japanese Road Association). Furthermore, the impact forces of rockfall from different heights on structure with soil cushions—plain filling soil, silty clay, and sandy silty soil each of different thicknesses—are analyzed. The cushioning capacity of soil is in exponential function relation with soil cushion's thickness and rockfall's height; while the influence of falling height on cushioning capacity does not change with the change of soil material. Given the same soil thickness, the cushion capacity of silty clay is the largest, followed by that of plain filling soil and sandy silty soil in sequence. From an economic point of view, the thickness of soil cushion is recommended to be within 2-3 meters in engineering practice.
引文
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[15] 石崇,徐卫亚. 颗粒流数值模拟技巧与实践[M]. 北京: 中国建筑工业出版社, 2015.
[2] 梁建强. 湖北兴山发生落石事故致5人死亡2人受伤[N/OL].中华网,(2015-4-22)[2016-08-26].http://news.xinhuanet.com/2015-04/22/c_1115051396.html.
[3] JTG D30—2004,公路路基设计规范[S]. 北京: 人民交通出版社, 2004.
[4] 铁道部第二勘测设计院. 铁路工程设计技术手册《隧道》[M]. 北京: 中国铁道出版社,1995.
[5] 杨其新,关宝树.落石冲击力计算方法的试验研究[J]. 铁道学报, 1996,18(1):101-106.
[6] 叶四桥,陈洪凯,唐红梅. 落石冲击力计算方法的比较研究[J]. 水文地质工程地质, 2010, 37(2):59-64.
[7] KAWAHARA S, MURO T. Effects of Dry Density and Thickness of Sandy Soil on Impact Response Due to Rockfall[J]. Journal of Terramechanics, 2006,43(3):329-340.
[8] LABIOUSE V, HEIDENREICH B. Half-scale Experimental Study of Rockfall Impacts on Sandy Slopes[J]. Natural Hazards and Earth System Sciences,2009, 9(6):1981-1993.
[9] PICHLER B, HELLMICH C, MANG H A. Determination of the Indentation Resistance of Gravel as the Basis for Safety prognoses of Gravel-buried Steel Pipelines Subjected to Rockfall[J]. Icf11 Italy, 2013,8(2):5572-5577.
[10] 王玉锁,李俊杰,李正辉,等. 落石冲击力评定的离散元颗粒流数值模拟[J]. 西南交通大学学报, 2016,51(1):22-29.
[11] 李爽,刘洋,吴可嘉. 砂土直剪试验离散元数值模拟与细观变形机理研究[J]. 长江科学院院报,2017,34(4):104-110,116.
[12] 苏明. 考虑颗粒破碎的粗粒料力学特性研究综述[J]. 长江科学院院报,2015,32(5):82-88.
[13] 徐士良,朱合华. 公路隧道通风竖井岩爆机制颗粒流模拟研究[J]. 岩土力学,2011,32(3):885-890,898.
[14] 孙新坡,何思明,樊晓一,等. 崩塌体与拦石墙冲击动力演化过程及参数敏感性[J]. 成都理工大学学报(自然科学版),2017,44(2):232-238.
[15] 石崇,徐卫亚. 颗粒流数值模拟技巧与实践[M]. 北京: 中国建筑工业出版社, 2015.