低围压水平下QH-E模拟月壤三轴试验技术与力学特性

Techniques for triaxial compression tests on simulant lunar soil QH-E and its mechanical behaviors under low confining stress

月球的低重力环境对月面浅层月壤力学特性的影响很大。利用清华大学取自吉林省靖宇县境内的火山灰岩研制出的模拟月壤（QH-E）,对GCTS公司生产的STX型动/应力路径三轴仪重新配置高精度的传感器,并采取专门的试验技术,成功实施了一系列低围压水平（3.13~25 k Pa）的三轴压缩试验。试验结果表明,在低围压水平下：模拟月壤具有显著的剪胀效应;与常规围压水平（50~150 k Pa）结果相比,同一相对密度模拟月壤的峰值摩擦角更高;相对密度越高,峰值摩擦角越大;切线模量和剪切模量均随着围压和相对密度的减小而减小;剪胀角随围压的减小和相对密度的增大而增大,且低围压水平下剪胀角对围压变化十分敏感。最后就低围压下QH-E模拟月壤与饱和砂土特性的差异,及重力场环境和施加围压的介质的影响进行了讨论。

A series of typical triaxial compression tests are conducted on simulant lunar soil QH-E, which is originated from cinerite from Jingyu County, Jilin Province and is developed by＇ Tsinghua University. For the triaxial compression tests on QH-E under low confining stress, highly sensitive transducers are used to measure the volume change in the water surrounding the triaxial test specimen and to control the confining stress. The test results indicate that the QH-E under low confining stresses （3.13 ~25 kPa） shows the conspicuous dilatancy behavior. Compared with the results from the conventional confining stresses （50~ 150 kPa）, the peak friction angle of QH-E under low confining stresses is larger. The higher the relative density of QH-E, the larger the peak friction angle. Both the tangent modulus and the shear modulus of QH-E decrease with the decrease of the confining stress and relative density, while the dilatancy angle increases with the decrease of the confining stress and the increase of the relative density. Moreover, under low confining stresses the differences of the properties between the QH-E in this study and the saturated sands in the literatures, and the influences of both the m0on/terrestrial environments and water in pressure chamber on the properties of QH-E, are discussed.