Eunhye Kim

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.

This study demonstrates possible scenarios of double-layered umbrella pipe system installed over a longwall take down room in a western coal mine, where holes are drilled and cased from an adjacent entry in advance of undermining. Finite difference analysis in FLAC 3D with strain hardening gob model is used because this method is a complex and rigorous way for solving boundary value problems, such stress and strain in a continuum and at an excavation boundary due to undermining. Support system was simulated with two different methods: composite material method and beam element method. We realized that the composite material method is very conservative compared to beam element method. Thus, in the rest of the simulation, we used the beam element method to investigate the effect of different angles of umbrella pipes on the roof support. To validate the modeling results, we compare the numeral modeling results with empirical formula widely used in subsidence calculation. Also, this computer simulation compared displacement of roof between in the presence and absence of this pipe umbrella support system. In this paper, we demonstrated that a relative stiffness increase ∼185% for a reinforced zone can decrease the displacement ∼ 12.5 cm (∼ 5 in.) in the longwall recovery room roof based on results from the equivalent stiffness method. This reduction is a substantial amount, which could be really beneficial to mine operators during mining processes.