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

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 moon/terrestrial environments and water in pressure chamber on the properties of QH-E, are discussed.