考虑颗粒破碎的堆石料湿化变形特性离散元模拟研究
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摘要
堆石料广泛应用于土石坝和山区机场地基的填筑工程中,其湿化变形可能会影响工程的正常使用甚至威胁其安全性。颗粒破碎是导致湿化变形的重要原因,然而目前对于堆石料湿化过程中颗粒的破碎规律尚不明晰。该文采用离散单元法,分别模拟了侧限条件下单线法和双线法湿化变形试验,比较了单、双线法湿化变形的差异。采用Hardin破碎率表征颗粒破碎量,分析了湿化过程中颗粒破碎量与填筑体应变及颗粒间摩擦耗能等的关系。此外,还讨论了湿化路径、颗粒形状、材料软化系数对湿化变形的影响。研究结果表明:侧限条件下湿化变形随应力水平增加而增加,且单线法测得的湿化变形大于双线法。湿化路径对总变形量有一定影响,先湿化后加载可有效降低总变形量。加载过程中,颗粒破碎以棱角破碎为主,且多棱角颗粒的试样湿化变形大于浑圆颗粒试样。Hardin破碎率与试样摩擦耗能的关系受湿化路径的影响,与应变的关系不受湿化路径的影响,仅与试样初始状态和材料特性有关。
Rockfill materials are widely used in civil engineering, such as dams, railways, and airport foundations in mountain areas. Significant wetting deformation may affect the serviceability or even the safety of rockfill infrastructure. Particle breakage is an important reason for wetting deformation. However, the relation between particle breakage and wetting deformation remains unclear and further study is necessary. The discrete element method was used to simulate single-line and double-line wetting tests, and the differences between the two methods were discussed. The relationships between particle breakage characterized by Hardin index, strain and friction energy were analyzed. Furthermore, the effect of wetting path, particle shape and softening coefficient on wetting deformation were investigated. The preliminary results showed that the wetting deformation increased with the stress applied, and larger wetting deformation was observed with the single-line method. During the loading process, particle breakage mainly occurs at the corners of particles. Angular particles experience more breakages and larger wetting deformation under one-dimensional compression than rounded particles. Moreover, the relationship between the Hardin index and friction energy dissipation is affected by the wetting path, while the relation between Hardin index and the strain is unique and depends exclusively on the initial density and intrinsic parameters of the material.
Rockfill materials are widely used in civil engineering, such as dams, railways, and airport foundations in mountain areas. Significant wetting deformation may affect the serviceability or even the safety of rockfill infrastructure. Particle breakage is an important reason for wetting deformation. However, the relation between particle breakage and wetting deformation remains unclear and further study is necessary. The discrete element method was used to simulate single-line and double-line wetting tests, and the differences between the two methods were discussed. The relationships between particle breakage characterized by Hardin index, strain and friction energy were analyzed. Furthermore, the effect of wetting path, particle shape and softening coefficient on wetting deformation were investigated. The preliminary results showed that the wetting deformation increased with the stress applied, and larger wetting deformation was observed with the single-line method. During the loading process, particle breakage mainly occurs at the corners of particles. Angular particles experience more breakages and larger wetting deformation under one-dimensional compression than rounded particles. Moreover, the relationship between the Hardin index and friction energy dissipation is affected by the wetting path, while the relation between Hardin index and the strain is unique and depends exclusively on the initial density and intrinsic parameters of the material.
引文
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[2]徐明,宋二祥.高填方长期工后沉降研究的综述[J].清华大学学报自然科学版,2009(6):786―789.Xu Ming,Song Erxiang.Review of long-term settling of high fills[J].Journal of Tsinghua University(Science and Technology),2009(6):786―789.(in Chinese)
[3]殷宗泽,费余绮,张金富.小浪底土坝坝料土的湿化变形试验研究[J].水利水电科技进展,1993(4):73―76.Yin Zongze,Fei Yuqi,Zhang Jinfu.Trixial test research on wetting deformation for materials of Xiaolangdi arch and rock fill dam[J].Advances in Science and Technology of Water Resources,1993,13(4):73―76.(in Chinese)
[4]李广信.堆石料的湿化试验和数学模型[J].岩土工程学报,1990,12(5):58―64.Li Guangxin.Experimental study and mathematic simulation on wetting behavior of rock fill[J].Chinese Journal of Geotechnical Engineering,1990,12(5):58―64.(in Chinese)
[5]左元明,沈珠江.坝壳砂砾料浸水变形特性的测定[J].南京水利水运工程学报,1989(1):107―113.Zuo Yuanming,Shen Zhujiang.Deformation character of gravel sand due to wetting[J].Journal of Nanjing Hydraulic Research Institute,1989(1):107―113.(in Chinese)
[6]曹光栩,宋二祥,徐明.碎石料干湿循环变形试验及计算方法[J].哈尔滨工业大学学报,2011,43(10):98―104.Cao Guangxu,Song Erxiang,Xu Ming.Study on experiment and calculation method of dry-wet cycle characteristics of rockfills[J].Journal of Harbin Institute of Technology,2011,43(10):98―104.(in Chinese)
[7]丁艳辉,袁会娜,张丙印.堆石料非饱和湿化变形特性试验研究[J].工程力学,2013,30(9):139―143.Ding Yanhui,Yuan Huina,Zhang Bingyin.Unsaturated wetting deformation characteristics of rockfill materials[J].Engineering Mechanics,2013,30(9):139―143.(in Chinese)
[8]Alonso E E,Romero E E,Ortega E.Yielding of rockfill in relative humidity-controlled triaxial experiments[J].Acta Geotechnica,2016,11(3):455―477.
[9]魏松,朱俊高.粗粒料三轴湿化颗粒破碎试验研究[J].岩石力学与工程学报,2006,25(6):1252―1258.Wei Song,Zhu Jungao.Study on wetting breakage of coarse-grained materials in triaxial test[J].Chinese Journal of Rock Mechanics and Engineering,2006,25(6):1252―1258.(in Chinese)
[10]Zhao Z H,Song E X.Particle mechanics modeling of creep behavior of rockfill materials under dry and wet conditions[J].Computers&Geotechnics,2015,68:137―146.
[11]Zhou M J,Song E X.A random virtual crack DEM model for creep behavior of rockfill based on the subcritical crack propagation theory[J].Acta Geotechnica,2016,11(4):827―847.
[12]Xu M,Hong J T,Song E X.DEM study on the effect of particle breakage on the macro-and micro-behavior of rockfill sheared along different stress paths[J].Computers&Geotechnics,2017,89:113―127.
[13]姜浩,徐明.碎石料应力路径大型三轴试验的离散元模拟研究[J].工程力学,2014,31(10):151―157.Jiang Hao,Xu Ming.Study of stress-path-dependent behavior of rockfills using discrete element method[J].Engineering Mechanics,2014,31(10):151―157.(in Chinese)
[14]Eeckhout E M V.The mechanisms of strength reduction due to moisture in coal mine shales[J].International Journal of Rock Mechanics&Mining Sciences&Geomechanics Abstracts,1976,13(2):61―67.
[15]Baud P,Zhu W,Wong T F.Failure mode and weakening effect of water on sandstone[J].Journal of Geophysical Research Solid Earth,2000,105(B7):16371―16389.
[16]Nakata Y,Hyodo M,Hyde A F L,et al.Microscopic particle crushing of sand subjected to high pressure one-dimensional compression[J].Soils&Foundations,2001,41(1):69―82.