TY - JOUR
T1 - Simulation of Lunar Soil With Irregularly Shaped, Crushable Grains
T2 - Effects of Grain Shapes on the Mechanical Behaviors
AU - Khademian, Zoheir
AU - Kim, Eunhye
AU - Nakagawa, Masami
N1 - Funding Information:
This work was supported by the Ryan Garvey Foundation (awarded to Dr. Eunhye Kim). The data used are listed in the figures and tables.
Publisher Copyright:
©2019. The Authors.
PY - 2019/5
Y1 - 2019/5
N2 - One of the challenges to overcome in Moon mining operations, such as soil handling, drilling, excavation, and wheeled movement, is understanding the mechanical behaviors of lunar soil, which is composed of grains characterized by highly irregular shapes. The impracticality of performing mechanical experiments on lunar soil samples has made computational techniques useful for exploring the mechanical behaviors of lunar soil. This paper uses particle flow code and describes a procedure for simulating lunar soil grains with specific size, shape, and strength distributions. We adopt data from soil samples 64501 and 60501 retrieved in Apollo 16. Lunar soil samples are simulated as assemblies of different shapes of grains consisting of rigid spheres connected through parallel bonds. We classify grains into four categories based on their shape: agglutinate, breccia A, breccia B, and plagioclase. We simulate each grain based on available imaging studies on their shape characteristics. We reveal the significance of grain shape irregularity through angle-of-repose tests on samples with and without irregularly shaped agglutinates. Results show that the shape irregularity increases the angle of repose by 6°. We repeat the test under different gravitational acceleration ranging from 0.1 to 25 m/s2 and show that for values below about 10 m/s2, the angle of repose is inversely related to the gravity but above 10 m/s2, remains independent of the gravity. We perform triaxial compression tests to investigate behaviors of simulated samples under confined loadings. The confinement varies from zero to 15 kPa, corresponding to the lateral in situ stress at depths up to 250 cm. The cohesion and friction angle derived from the triaxial tests are shown to agree with the lab and in situ measurements. This numerical practice and presented methodology pave the way for full-scale simulation of mining operations on the Moon surface.
AB - One of the challenges to overcome in Moon mining operations, such as soil handling, drilling, excavation, and wheeled movement, is understanding the mechanical behaviors of lunar soil, which is composed of grains characterized by highly irregular shapes. The impracticality of performing mechanical experiments on lunar soil samples has made computational techniques useful for exploring the mechanical behaviors of lunar soil. This paper uses particle flow code and describes a procedure for simulating lunar soil grains with specific size, shape, and strength distributions. We adopt data from soil samples 64501 and 60501 retrieved in Apollo 16. Lunar soil samples are simulated as assemblies of different shapes of grains consisting of rigid spheres connected through parallel bonds. We classify grains into four categories based on their shape: agglutinate, breccia A, breccia B, and plagioclase. We simulate each grain based on available imaging studies on their shape characteristics. We reveal the significance of grain shape irregularity through angle-of-repose tests on samples with and without irregularly shaped agglutinates. Results show that the shape irregularity increases the angle of repose by 6°. We repeat the test under different gravitational acceleration ranging from 0.1 to 25 m/s2 and show that for values below about 10 m/s2, the angle of repose is inversely related to the gravity but above 10 m/s2, remains independent of the gravity. We perform triaxial compression tests to investigate behaviors of simulated samples under confined loadings. The confinement varies from zero to 15 kPa, corresponding to the lateral in situ stress at depths up to 250 cm. The cohesion and friction angle derived from the triaxial tests are shown to agree with the lab and in situ measurements. This numerical practice and presented methodology pave the way for full-scale simulation of mining operations on the Moon surface.
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U2 - 10.1029/2018JE005889
DO - 10.1029/2018JE005889
M3 - Article
AN - SCOPUS:85065239249
SN - 2169-9097
VL - 124
SP - 1157
EP - 1176
JO - Journal of Geophysical Research: Planets
JF - Journal of Geophysical Research: Planets
IS - 5
ER -