用于颗粒土微观力学行为试验的微型三轴试验仪

颗粒土的微观力学行为（如土颗粒的运动与破碎等）决定着其宏观应力-应变行为，如应变局部化、应力硬化等。为研究颗粒土的微观力学行为，开发了一台微型三轴试验装置。它的轴向加载系统由伺服控制的步进转动马达与涡轮传动的减速器组成，围压由GDS压力控制器提供，压力室采用高透光率，高强度的轻质材料制成。借助于X射线显微CT及图像处理分析技术，该装置能实现对干砂土微尺寸试样（直径为8 mm，高度为16 mm）在三轴剪切条件下微观特性的无损检测。采用该三轴试验装置对粒径为0.60～1.18 mm 的LBS（Leighton Buzzard sand）试样在1.5 MPa的围压下进行了试验。结果显示，试验装置测得应力-应变曲线合理，显微CT 图像特征清晰，能够用于颗粒土体微观土力学行为的试验研究。

A mini-triaxial apparatus for testing of micro-scale mechanical behavior of granular soils

The micro-scale mechanical behavior of granular soils (e.g., particle movement and particle breakage, etc.) governs their macro-scale stress and strain behavior, such as strain localization and stress hardening, etc. To study the micro-scale mechanical behavior of granular soils, a mini-triaxial apparatus is developed in this paper. The axial loading system of the apparatus is composed of a servo-controlled stepping motor and turbine-driven reducer. The confining pressure is provided by a GDS pressure generator, and the chamber is fabricated with a highly transparent material with high strength and low density. In conjunction with an X-ray micro CT image processing and analysis techniques, this apparatus can be used for non-destructive detection of the micro-scale characteristics of a mini dry sample (i.e., 8 mm in diameter and 16 mm in height) under triaxial shearing. A triaxial test of a Leighton Buzzard sand (LBS) sample with an initial grading of 0.60-1.18 mm under a confining pressure of 1.5 MPa is carried out using this apparatus. The results show a reasonable stress-strain curve and CT images with easily distinguishable features, which demonstrates that the apparatus can be used for testing of the micro-scale mechanical behavior of granular soils.