Mechanical Properties of QH-E Lunar Soil Simulant at Low Confining Stresses

Abstract

The low-moon gravity has a significant influence on the mechanical properties of lunar soils at low-stress levels. To better understand the shear strength and deformation behavior of lunar soils at low confining stress and to facilitate the modeling and simulation of lunar activities, a series of consolidated drained triaxial compression tests were performed on numerous samples of lunar-soil simulant developed by Tsinghua University, China (named as QH-E). Great care was taken to conduct the experimental studies at low confining stresses such that reliable results can be obtained. The measured data suggest that QH-E samples exhibited strain-softening behavior with typical residual shear strength behavior characteristics. It was also found the residual internal friction angle φcs approximately 40°, regardless of confining stress, σ3 and relative density, Dr, whereas the peak apparent cohesion intercept ca−p is not equal to zero owing to the nonlinear behavior of shear strength of QH-E. However, the residual value of apparent cohesion intercept ca−cs is equal to zero. The rate of change of dilatancy angle at low confining stress values is greater than those at the conventional confining stress values. Further, based on the measured data from this study, two empirical models were suggested to predict the tangent modulus E and shear modulus G of QH-E at low confining stress, and according to the prediction models for internal friction angle and dilatancy angle in the literature, the model parameters of QH-E at low confining stress were determined.