考虑不同边界条件的风积沙-土工格栅拉拔试验离散元模拟研究  

Discrete element simulation on aeolian sand-geogrid pull-out test with different boundary conditions

作　　者：杜炜 聂如松[1,2] 李列列 谭永长 张杰 祁延录 DU Wei;NIE Ru-song;LI Lie-lie;TAN Yong-chang;ZHANG Jie;QI Yan-lu(School of Civil Engineering,Central South University,Changsha,Hunan 410075,China;MOE Key Laboratory of Engineering Structures of Heavy Haul Railway,Central South University,Changsha,Hunan 410075,China;College of Water Resources and Hydropower,North China University of Water Resources and Electric Power,Zhengzhou,Henan 450045,China;Xinjiang Railway Survey and Design Institute Co.,Ltd.,Urumqi,Xinjiang 830011,China)

机构地区：[1]中南大学土木工程学院,湖南长沙410075 [2]中南大学重载铁路工程结构教育部重点实验室,湖南长沙410075 [3]华北水利水电大学水利水电学院,河南郑州450045 [4]新疆铁道勘察设计院有限公司,新疆乌鲁木齐830011

出　　处：《岩土力学》2023年第6期1849-1862,共14页Rock and Soil Mechanics

基　　金：中国铁路乌鲁木齐局集团有限公司科技研究开发计划课题(No.WLMQ-KGHZGS-HRTL-GGB-2020-0032);国家自然科学基金(No.51878666);高速铁路建造技术国家工程实验室开放基金项目(No.HSR201905)。

摘　　要：室内土工格栅拉拔试验物理模型边界及加载装置通常是刚性的,但土工格栅工程应用的边界条件往往不能与室内拉拔试验物理模型边界相对应。为了研究边界条件对拉拔试验结果的影响,在室内三轴和拉拔试验的基础上,运用三维离散元方法,对土工格栅加筋风积沙的拉拔试验展开数值模拟,研究加载顶面刚、柔性加载方式和模型前壁刚、柔性边界4种组合条件即刚性顶面刚性前壁(RTRP)、柔性顶面刚性前壁(FTRP)、刚性顶面柔性前壁(R_(T)F_(P))、柔性顶面柔性前壁(F_(T)F_(P))对筋土界面宏细观特性的影响。分析了不同组合条件下拉拔力与拉拔位移的关系、界面剪切强度、试样内部应力链、孔隙率分布和颗粒旋转规律,分析了刚性加载板和柔性边界颗粒位移、F_(T)F_(P)组合下土工格栅的变形以及拉拔过程中剪切带的演化规律。研究表明,模型前壁的刚、柔性边界对拉拔力和拉拔位移曲线模式以及界面摩擦角的影响很大。刚性前壁边界条件下,拉拔力和拉拔位移曲线呈加工软化型;柔性前壁边界条件下,拉拔力和拉拔位移曲线近似呈双折线型。当模型前壁由刚性变为柔性时,界面摩擦角减小了7°~8°。当法向应力小于90kPa时,建议FTRP组合、R_(T)F_(P)组合和F_(T)F_(P)组合的拉拔力峰值折减系数分别取0.9、0.6和0.7。4种组合在拉拔试验过程中试样体积增加,呈剪胀特性。RTRP和FTRP组合剪切带厚度分布为颗粒平均粒径的5.38倍和10.79倍;R_(T)F_(P)与F_(T)F_(P)组合剪切带的分布范围更广。该研究成果有助于深入揭示刚、柔加载方式以及刚、柔前壁边界下土工合成材料和风积沙的相互作用机制。The boundary and loading device of the physical model of laboratory geogrid pull-out tests are usually rigid,but the boundary conditions of the geogrid in engineering application cannot always correspond to the physical model boundary of laboratory pull-out test.In order to study the effect of boundary conditions on the pull-out test results,this paper uses three-dimensional discrete element method to carry out numerical simulation on the pull-out tests of geogrid-reinforced aeolian sand based on the laboratory triaxial and pull-out tests.The effects of four combination conditions,namely rigid top surface and rigid front wall(RTRP),flexible top surface and rigid front wall(FTRP),rigid top surface and flexible front wall(R_(T)F_(P)),and flexible top surface and flexible front wall(F_(T)F_(P)),on the macroscopic and mesoscopic characteristics of reinforced soil interface are studied.The relationship between pull-out force and pull-out displacement,interface shear strength,force chain,porosity distribution and particle rotation law were analyzed under different combination conditions.The displacement of rigid loading plate and flexible boundary particles,the deformation of geogrids under F_(T)F_(P) combination,and the evolution law of shear band during pull-out were examined.The results show that the rigid and flexible boundary of the front wall of the model has a great influence on the pull-out force curve pattern and interface friction angle.Under rigid front wall boundary conditions,the pull-out force and displacement curves are machining softening,while the pull force and displacement curves are approximately double-folded under the boundary condition of flexible front wall.When the front wall of the model changes from rigid to flexible,the friction angle of the interface decreases by 7º−8º.When the normal pressure is less than 90 kPa,it is suggested that the peak reduction coefficients of the FTRP combination,R_(T)F_(P) combination and F_(T)F_(P) combination should be 0.9,0.6 and 0.7,respectively.In the pro

关 键 词：拉拔试验 边界条件 离散元法 风积沙 

分 类 号：TU411[建筑科学—岩土工程]