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Description
With plans of establishing human settlements on the moon, extraction and utilization of water resources from the lunar subsurface arose as one of the hot research topics in geotechnics. Through lunar explorations, water ice was detected at the PSRs (Permanently Shadowed Regions) of several lunar craters. Several sites are deemed to hold relatively large amount of water ice, however, the detailed information on the lunar geology is yet a mystery. To study the geophysical and geomechanical characteristics of the lunar soils, artificial simulants that duplicate the mineralogy of the lunar soils are frequently used. Use of lunar simulants are due to the scarcity of the real lunar soils retrieved from the Moon. Using available lunar simulants and based on the collected knowledge of the lunar geology, an experimental study was conducted to observe the geophysical and geomechanical behaviour of frozen lunar soils.
Among many types of lunar simulants, LMS-1 (Lunar Mare Simulant) was used for the study. A total of eight cylindrical samples were created with varying water content, dry density, and with two different sample preparation methods. Dry pluviation and moist tamping techniques were adopted for the sample preparation methods. The samples had dimensions of 25.4mm in diameter and 50.8mm in height. The compacted specimens were frozen inside a freezer for a minimum of 24 hours and tested inside the climate chamber at a constant temperature of -9°C. Wave velocities, electrical resistivities and unconfined compressive strengths (UCS) were measured for all eight samples, and among them, four samples were scanned using a CT scanner to observe the homogeneity of the samples that were prepared using two different sample preparation methods.
The results indicated that the geophysical and geomechanical behaviour was highly dependent on the water content of the material. The shear wave velocities were increasing with increase in water content while the effect of dry density was relatively less pronounced. The electrical resistivity showed an opposite trend where the increase in water content yielded a decrease in electrical resistivity. For the UCS, the higher water content had stronger compressive strength. The UCS was also dependent on the dry density of the material where an increase in dry density led to an increase in UCS. The CT scans of dry pluviation was relatively more homogenous compared to the moist tamped samples. The experimental results, however, did not indicate significant differences between the two chosen preparation methods.
References
geophysical and geomechanical behaviour of frozen lunar simulants. - Kim (2023)
| Keywords | Lunar soil, geotechnics, geophysics, laboratory experiment |
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