摘要
常规动三轴试验不能实现试样细观结构的观测,对原有CKC型振动三轴仪实施可视化改进,开发用于试验过程试样细观结构观测的试验系统。在砂土振动液化试验中,利用显微数码摄录技术全程动态摄录整个试验过程砂土细观结构的变化,从摄录录像中提取特征时刻的数字图像照片,导入自主开发的数字图像细观结构分析软件DeoDIP,对比分析液化前后砂土细观结构(颗粒定向性、接触法向、接触数)的演化规律,追踪标志砂颗粒的运动轨迹。结果表明:液化时,颗粒长轴没有明显的优选方向,制样引起的初始各向异性被消除;接触法向呈现各向异性特征,其主方向在整个试验过程中一直偏于竖直方向;平均接触数发生了损失,液化排水后得到恢复,说明试样振动密实。液化前,各标志颗粒具有基本相同的运动轨迹,颗粒运动以平动为主,旋转作用很小,颗粒运动与试样变形保持较好的整体性;颗粒之间相对运动加剧,颗粒之间不断接触分离,部分颗粒出现悬浮现象,且颗粒旋转明显。可视化三轴试验结果不仅有助于研究砂土液化的细观力学机理,并能为液化细观数值模拟提供试验基础。
A modified CKC cyclic triaxial apparatus is used to monitor the evolution of granular soil microstructures during cyclic triaxial tests.Micro digital screening techniques are used to capture the change of microstructures of sand samples during liquefaction induced by cyclic loading.Digital images at certain stages of the tests are cut from the videos and further processed by self-developed software named GeoDIP.The microfabric evolutions including particle orientation,contact normal and number of contacts are analyzed.Labeled particles are traced to study the micro mechanism of soil deformation.It is found that there is no preferred orientation of the long axes of particles in liquefied samples.The main direction of contact normal between particles orients vertically whether the sample is liquefied or not.The samples experience a significant loss of contact number during liquefaction,but the number regains a lot after post-liquefaction drainage.Soil particles exhibit obvious translational motion before liquefaction,but start to move relatively and rotate when liquefaction occurs.The results of this study can not only explore the micro mechanism of sand liquefaction,but also provide an experimental basis for numerical modeling of sand liquefaction.
出处
《岩土工程学报》
EI
CAS
CSCD
北大核心
2011年第1期81-87,共7页
Chinese Journal of Geotechnical Engineering
基金
国家自然科学基金项目(90815008
50909057)
同济大学岩土及地下工程教育部重点实验室开放基金项目(KLE-TJGE-0904)
关键词
砂土液化
可视化动三轴试验
细观结构
组构各向异性
颗粒旋转
sand liquefaction
visualized cyclic triaxial test
microstructure
fabric anisotropy
particle rotation
