工程粘性土微观结构的定量评价

QUANTITATIVE APPROACH ON MICRO-STRUCTURE OF ENGINEERING CLAY

本文首先介绍了作者研制的温差真空干燥系统和作者同合肥工业大学一道研制的土体微观结构图片计算机定量分析系统,前者用于速冻粘土试样的干燥处理以保证其原始结构不受扰动,后者用于土结构图象的定量分析。从工程土体的系统性出发,作者提出了工程土的结构层次、结构状态以及结构状态熵的概念;另外,在不同压力和不同作用时间下对宁波粘土进行了结构定量分析,文中叙述了粘土结构状态参数——结构熵、结构单元的平均粒径、平均形状系数的变化规律,分析了结构变化与粘土特殊物理力学性质之间的关系。

This present paper concerns with the micro-structure of engineering clay and the method as well as the equipments to deal with it.At first, two instruments are introduced, one of them is a Temperature Gradient Vacuum Sublimation System designed by the author to dry the quiekly freezen samples of undisturbed clay. The success in developing of this equipment highly raises the degree to keep samples for structure analysis undisturbed, which has supplied reliable premise for later work; another equipment is a computed image processing system developed by the author & Hefei Polytechnic University for quantitatively studying of the micro-structure from clay's micro-images, by which, more quantitative informations about clay's micro-structure can be gotten.With system ideas, the these is analyses theoretically the engineering clay as a system, dividing the levels of clay structure, pointing out the main structure levels. It is concluded that the system of engineering clay has not fixed structure pattern but the structure state that may relatively stable at certain time and changes from one state to another with the variation of engineering circumstances. It is suggested that the confusion degree of the connections between clay particles can be used as quantitative parameter reflecting clay structure state and raised the concept of the entropy of structure state, pointing out its properties.From mechanic tests and structure analysis on Ningbo clay, following facts have been found:( 1 ) The arrangment entropy of clay reduces by logarithm with time under the charge of certain pressure.( 2 ) The entropy of clay goes down by logarithm with the increase of pressure.( 3 ) In average values, the area of particles of clay become bigger when pressure get to certain value, and the bigger the pressure is, the quicker the increase rate is.( 4 ) The average shape parameter of particles of clay is also becoming bigger with the increasing of pressure. This reflects that the particles are becoming flater and flater.It may be considered that these phenomenon of structure change of clay that are different from the other materials is the source of the special mechanical properties of clay system. Based on the changes of structure parameters of clay under charge of pressure stress and time, the mechanism of clay's behaviours under pressure has analysed, pointing out that the structure evolution is the internal facter of all properties and functions of clay.Finally, The paper points out possible foreground of utilities of micro-structure parameters by studying the relations between structure parameters and the engineering properties of clay.