适用于显微CT扫描的微型动三轴仪研制与试验验证

Development of miniature dynamic triaxial apparatus for microct scanning and its experimental verification

土体的微观结构对其宏观力学性质有着很大的影响,为了能更深入研究土体在循环荷载作用下的微观结构演化与其宏观力学特性之间的联系,研制了一种适用于工业显微CT(computerizedtomography)扫描的微型动三轴仪。该仪器主要由控制采集箱系统、主机系统、气水转换器组成。其具有体积较小、试样小型化(直径×高=10 mm×20 mm)、便于操作、兼容性强等优点,可在无需改装已有CT设备前提下对试样进行旋转扫描。以丰浦砂干砂样为材料,采用微型和常规动三轴仪进行了不同围压(50,100,200,300 k Pa)和循环荷载作用下的不固结不排水试验,并对测得的初始动弹性模量E_(0),动剪切模量G_(d),阻尼比l进行了对比分析。结果表明:微型动三轴仪测得的初始动弹性模量E_(0),动剪切模量G_(d),阻尼比λ与常规动三轴仪测得的结果基本相近。试验结果误差较小,验证了该仪器的可靠性。

The microstructure of soil has a great influence on the macroscopic mechanical properties.Therefore,to study the relationship between the macroscopic mechanical properties and the microstructure evolution of soil under the cyclic loading,a miniature dynamic triaxial apparatus is developed,which is suitable for industrial micro CT(computerized tomography)scanning.The apparatus is mainly composed of the acquisition control system,loading device system,and air-liquid converter.It has the advantages of small volume,miniaturization of the specimen(diameter×height=10 mm×20 mm),convenient to operate,strong compatibility,and the specimen can be rotating-scanned without refitting the existing CT equipment.By using the miniature dynamic triaxial apparatus and conventional dynamic triaxial apparatus,a series of unconsolidated-undrained triaxial tests on Toyoura sand under cyclic loading and different confining pressures(50,100,200 and 300 kPa)are carried out,and the initial dynamic elastic modulus(E_(0)),dynamic shear modulus(G_(d))and damping ratio(l)are comparatively analyzed.The results show that the experimental curves of the initial dynamic elastic modulus(E_(0)),dynamic shear modulus(G_(d))and damping ratio(l)exhibit a similar evolution.The difference of experimental data is small,thus,the reliability of the miniature dynamic triaxial apparatus is verified.