Discrete Element Modeling of Strength Properties and Failure Modes of Qh-E Lunar Soil Simulant at Low Confining Stresses

Abstract

In this paper, discrete element method (DEM) is used to investigate the strength properties and failure modes of QH-E lunar soil simulant at the low confining stress. The deviator stress-axial strain curves and volumetric strain-axial strain curves are obtained based on DEM simulations, which are basically consistent with the experimental results at the low confining stresses, and the lower confining stress is, the closer to the experimental curves will obtain. Moreover, for a given low confining stress, the effects of porosity and friction coefficient on strength properties of QH-E samples are discussed. The results show that the peak stress, residual stress and axial strain corresponding to the peak stress obviously decrease with the increase of the porosity, while slightly increase with the increase of the friction coefficient. Furthermore, the whole failure processes and failure modes at different low confining stresses are also observed by DEM simulations. The simulated results indicate that the V-type shear zone (double shear bands) is the main failure mode at the low confining stress, and then the V-type shear zone gradually changes to a single shear band (along the horizontal direction about 52 o) with the increase of the confining stress.

Discrete Element Modelling of Triaxial Compression Test of QH-E Lunar Soil Simulant under Hydrostatic Compression

“…In the geotechnical problem of lunar soil PFC numerical simulation, parallel-bonded model is used to study the triaxial compression mechanical properties of lunar soil simulant because lunar soil has a certain amount of apparent cohesion [19], [20], which has been successfully applied to simulate mechanical properties of lunar soil simulant [4], [17], [18]. By drawing the Mohr's circles and their common tangent based on our previous experimental data [8], the average cohesion is 3.1 kPa and the friction angle is 51.55°, whereas the average cohesion is 18.80 kPa and the friction angle is 48.17° for QH-E lunar soil simulant with particle density of 1640 kg/m3 at low and conventional stress levels, respectively.…”

“…Due to the mechanical properties of soil are not only closely related to the loading environment but also depend on stress paths and directions in granular materials [15], [16]. In our previous work, the strength and deformation behavior of QH-E lunar simulant under conventional triaxial compression path and constant mean principal stress path have been studied by 3-dimension particle flow code (PFC3D) numerical simulations [17], [18], however, the volume-change behavior of QH-E lunar simulant under hydrostatic compression path has not been studied well enough in geotechnical engineering literature.…”

Study on Mechanical Properties of QH-E Lunar Soil Simulant under Conventional Triaxial and Cyclic Triaxial Tests

“…The discrete element method (DEM) is becoming an emerging research direction in the field of lunar soil to study the basic physical, mechanical, and geotechnical engineering properties of lunar soil and numerical simulation of the interaction between lunar probes and lunar soil. Particle flow code (PFC) as an effective discrete element numerical simulation method, has been widely applied to investigate the mechanical behaviors of lunar soil under triaxial compression tests [15][16][17][18]. In our previous studies [16][17][18], PFC3D simulations were performed to investigate the static mechanical behaviors (strength and deformation characteristics) of QH-E lunar soil simulant under triaxial compression tests.…”

“…Particle flow code (PFC) as an effective discrete element numerical simulation method, has been widely applied to investigate the mechanical behaviors of lunar soil under triaxial compression tests [15][16][17][18]. In our previous studies [16][17][18], PFC3D simulations were performed to investigate the static mechanical behaviors (strength and deformation characteristics) of QH-E lunar soil simulant under triaxial compression tests. In this paper, the static and dynamic characteristics of QH-E lunar soil simulant under conventional triaxial and cyclic triaxial tests are further investigated by using PFC3D simulations.…”

Relation between Microstructures and Macroscopic Mechanical Properties of Earthen-Site Soils

“…With the rapid development of computer technology, the study of mechanical behavior extends from laboratory and field tests to numerical simulation. Particle agglomerates modeled by particle flow codes were used to investigate the effects of size [ 37 ], porosity, and friction coefficient [ 38 ] on strength properties of soils. The two-dimensional particle assembly model can study the influence of contact laws [ 39 ], particle shape [ 40 ], and particle breakage [ 41 , 42 , 43 ] on mechanical parameters, and simulate various laboratory tests to capture the macroscopic behavior of granular media [ 44 , 45 , 46 ].…”