粗粒土颗粒接触力学特性及细观接触模型研究
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摘要
将石灰岩粗粒土颗粒之间的接触形式简化为点–面接触,通过颗粒接触试验研究粗粒土的粒间法向、切向接触力学特性,并归纳出粗颗粒细观接触模型的具体形式。利用该细观模型,对粗粒土大型直剪试验进行离散元(PFC)数值模拟,通过数值计算结果与试验实测数据进行对比,验证粒间接触模型及细观参数的适用性。最后,对粗粒土颗粒接触特性及其接触模型的进一步深入研究进行分析和讨论。研究结果显示,实测的粒间接触力与接触位移关系曲线可以利用指数小于1的幂函数进行拟合;同时,为了对切向接触刚度进行统一的衡量,定义切向位移为5 mm时的切向力为切向接触强度(切向力有峰值时取峰值切向力)。对比大直剪试验的实测与计算结果发现,粒径较大(2~5,1~2 cm)时计算误差非常小;但对于含有更细小颗粒的级配试样,计算误差偏高。在细观尺度内,颗粒粒径在何种范围内会表现出与大颗粒不同的接触性质,有待借助更精细设备进一步探究。
The inter-particle contact of coarse-grained soils consist of limestone is simplified as point-surface contact. The particle contact models of coarse-grained soils are obtained through experimental investigation on the normal and tangential contact properties. The large shear tests of coarse-grained soils are simulated numerically with the discrete element method(PFC) using proposed micro contact models. The contact models and micro parameters are verified by comparing simulated results with measured data. The contact behaviors and contact models of coarse-grained soils are further discussed. The results show that the relationship between contact forces and displacements are fitted with power functions with an exponent less than 1. In order to measure the tangential contact stiffness,the tangential force corresponding to the tangential displacement of 5 mm is defined as the tangential contact strength,particularly,the peak tangential force is defined as the contact strength if a peak value occurs. Comparing the simulated results of large shear tests with measured data shows that the calculation errors are really small for soils with large particle diameters(2–5,1–2 cm). For the grading samples with smaller granules,the calculation errors are larger.
The inter-particle contact of coarse-grained soils consist of limestone is simplified as point-surface contact. The particle contact models of coarse-grained soils are obtained through experimental investigation on the normal and tangential contact properties. The large shear tests of coarse-grained soils are simulated numerically with the discrete element method(PFC) using proposed micro contact models. The contact models and micro parameters are verified by comparing simulated results with measured data. The contact behaviors and contact models of coarse-grained soils are further discussed. The results show that the relationship between contact forces and displacements are fitted with power functions with an exponent less than 1. In order to measure the tangential contact stiffness,the tangential force corresponding to the tangential displacement of 5 mm is defined as the tangential contact strength,particularly,the peak tangential force is defined as the contact strength if a peak value occurs. Comparing the simulated results of large shear tests with measured data shows that the calculation errors are really small for soils with large particle diameters(2–5,1–2 cm). For the grading samples with smaller granules,the calculation errors are larger.
引文
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[19]HARDIN B O.Crushing of soil particles[J].Journal of Geotechnical Engineering,1985,111(10):1 177–1 192.
[2]迟世春,周雄雄.堆石料的湿化变形模型[J].岩土工程学报,2017,39(1):48–55.(CHI Shichun,ZHOU Xiongxiong.Slaking deformation model for rockfill materials[J].Chinese Journal of Geotechnical Engineering,2017,39(1):48–55.(in Chinese))
[3]FU W X,ZHENG X,LEI X Z,et al.Using a modified direct shear apparatus to explore gap and size effects on shear resistance of coarse-grained soil[J].Particuology,2015,23(6):82–89.
[4]潘家军,程展林,余挺,等.不同中主应力条件下粗粒土应力变形特性试验研究[J].岩土工程学报,2016,38(11):2 078–2 084.(PAN Jiajun,CHENG Zhanlin,YU Ting,et al.Experimental study on stress-strain characteristics of coarse-grained soil under different intermediate principal stresses[J].Chinese Journal of Geotechnical Engineering,2016,38(11):2 078–2 084.(in Chinese))
[5]周文权,冷伍明,刘文劼,等.低围压循环荷载作用下饱和粗粒土的动力特性与骨干曲线模型研究[J].岩土力学,2016,37(2):415–423.(ZHOU Wenquan,LENG Wuming,LIU Wenjie,et al.Dynamic behavior and backbone curve model of saturated coarsegrained soil under cyclic loading and low confining pressure[J].Rock and Soil Mechanics,2016,37(2):415–423.(in Chinese))
[6]CHOO H,KIM J,LEE W,et al.Relationship between hydraulic conductivity and formation factor of coarse-grained soils as a function of particle size[J].Journal of Applied Geophysics,2016,127:91–101.
[7]FARGNOLI V,BOLDINI D,AMOROSI A.Twin tunnel excavation in coarse grained soils:observations and numerical back-predictions under free field conditions and in presence of a surface structure[J].Tunnelling and Underground Space Technology,2015,49:454–469.
[8]杨鸽,朱晟.考虑堆石料空间变异性的土石坝地震反应随机有限元分析[J].岩土工程学报,2016,38(10):1 822–1 832.(YANG Ge,ZHU Sheng.Seismic response of rockfill dams considering spatial variability of rockfill materials via random finite element method[J].Chinese Journal of Geotechnical Engineering,2016,38(10):1 822–1 832.(in Chinese))
[9]魏匡民,陈生水,李国英,等.基于状态参数的筑坝粗粒土本构模型[J].岩土工程学报,2016,38(4):654–661.(WEI Kuangmin,CHEN Shengshui,LI Guoying,et al.Constitutive model for coarse-grained dam materials considering state parameter[J].Chinese Journal of Geotechnical Engineering,2016,38(4):654–661.(in Chinese))
[10]JIANG J W,XIANG W,ROHN J,et al.Research on mechanical parameters of coarse-grained sliding soil based on CT scanning and numerical tests[J].Landslides,2016,13(5):1 261–1 272.
[11]ALIKARAMIC R C,ANDO E,GKIOUSAS-KAPNISIS M,et al.Strain localisation and grain breakage in sand under shearing at high mean stress:insights from in situ X-ray tomography[J].Acta Geotechnica,2015,10(1):15–30.
[12]蔡正银,李小梅,关云飞,等.堆石料的颗粒破碎规律研究[J].岩土工程学报,2016,38(5):923–929.(CAI Zhengyin,LI Xiaomei,GUAN Yunfei,et al.Particle breakage rules of rockfill mater ials[J].Chinese Journal of Geotechnical Engineering,2016,38(5):923–929.(in Chinese))
[13]NASEHI S A,UROMEIHY A,NIKUDEL M R,et al.Influence of gas oil contamination on geotechnical properties of fine and coarsegrained soils[J].Geotechnical and Geological Engineering,2016,34(1):333–345.
[14]KHUNTIA S,MUJTABA H,PATRA C,et al.Prediction of compaction parameters of coarse grained soil using multivariate adaptive regression splines(MARS)[J].International Journal of Geotechnical Engineering,2015,9(1):79–88.
[15]张季如,张弼文,胡泳,等.粒状岩土材料颗粒破碎演化规律的模型预测研究[J].岩石力学与工程学报,2016,35(9):1 898–1 905.(ZHANG Jiru,ZHANG Biwen,HU Yong,et al.Predicting the particle breakage of granular geomaterials[J].Chinese Journal of Rock Mechanics and Engineering,2016,35(9):1 898–1 905.(in Chinese))
[16]徐文杰,王识.基于真实块石形态的土石混合体细观力学三维数值直剪试验研究[J].岩石力学与工程学报,2016,35(10):2 152–2 160.(XU Wenjie,WANG Shi.Meso-mechanics of soil-rock mixture with real shape of rock blocks based on 3D numerical direct shear test[J].Chinese Journal of Rock Mechanics and Engineering,2016,35(10):2 152–2 160.(in Chinese))
[17]周健,张津,王强强.石膏颗粒接触试验研究[J].同济大学学报:自然科学版,2016,44(1):67–72.(ZHOU Jian,ZHANG Jin,WANG Qiangqiang.Experimental study on contact of gypsum particles[J].Journal of Tongji University:Natural Science,2016,44(1):67–72.(in Chinese))
[18]JIANG M J,YU H S,LEROUEIL S.A simple and efficient approach to capturing bonding effect in naturally microstructured sands by discrete element method[J].International Journal for Numerical Methods in Engineering,2007,69(6):1 158–1 193.
[19]HARDIN B O.Crushing of soil particles[J].Journal of Geotechnical Engineering,1985,111(10):1 177–1 192.