【作者】 肖瑞； 张巍； 许林； 施斌； 唐心煜； 梁小龙；

【Author】 XIAO Rui;ZHANG Wei;XU Lin;SHI Bin;TANG Xinyu;LIANG Xiaolong;School of Earth Sciences and Engineering,Nanjing University;

【机构】 南京大学地球科学与工程学院；

【摘要】 砂土三轴试验中孔隙结构的演化规律与其力学性质和强度特征之间存在着重要关系。本文基于同步辐射显微CT扫描,结合南京河西粉细砂的三轴压缩实验,采用自主研发的土体细微观三轴压缩在线观测控制系统,得到了南京粉细砂饱和试样在不同围压下加载过程中孔隙结构的实时扫描图像。通过ImageJ和Avizo软件对扫描图像进行三维重构,获取砂土试样在加载过程中的孔隙结构空间图像,然后简化为孔隙网络模型,采用孔隙率、孔隙形状、孔隙半径等指标分析孔隙结构的演变过程。可以得到以下结论:(1)松散南京粉细砂在低围压下表现出典型的应变软化特征,随着围压的增大开始表现出应变软化-硬化的特征;(2)中密南京粉细砂均表现出应变软化-硬化特征,即由剪缩向剪胀转变,因此可以用孔隙率来表示峰值强度与残余强度的关系;(3)小孔隙相互连通是导致大孔隙出现的原因,进而使松散南京粉细砂出现"准稳态"状态。更多还原

【Abstract】 In the three axis test of sand,there is an important relationship between the evolution of pore structure and its mechanical properties and strength characteristics.This paper based on synchrotron radiation micro CT scanning,combined with three axial compression experiment of silty sand soil in Hexi area of Nanjing,using self-developed micro three axis compression observation control system online,get images of Nanjing fine sand saturated pores in the load under different confining pressure in the process of structure in real time.Three-dimensional reconstruction of scanned image by ImageJ and Avizo software,get the pore structure of space image of the sand sample in the loading process,and then simplified as pore network model,then porosity,pore shape and pore radius were used to analyze the pore structure evolution.The results show that:(1) the loose condition of Nanjing fine sand under pressure showed typical strain softening characteristics of low confining,with the increase of confining pressure began to show characteristics of strain softening-hardening;(2) in the moderate compact state,the Nanjing fine sand showed a strain softening-hardening characteristic during the triaxial compression test,that is,from the shear state to the dilatancy state.Therefore,the porosity can be used to express the relationship between the porosity of peak strength and residual strength.(3) the interconnection of small pores is the cause of the emergence of large pores,which led to the loose condition of Naniine;fine sand appeared "quasi-steady state".更多还原