# Research on the Compactness of Lunar Soil Simulant Based on Static Cone Penetration Test
## 1 Introduction  
Lunar construction represents a bottleneck that urgently needs to be overcome for future exploration. Conducting construction on the lunar surface and establishing lunar bases are of great significance for enabling long-term human habitation on the Moon [1]. The heterogeneity of lunar soil at different depths presents formidable challenges to the construction of lunar bases. This characteristic is likely to cause the failure of the drilling process and pose instability-related risks to lunar bases. The static cone penetration test was first carried out during the Apollo and Luna landing programs, allowing the physical and mechanical properties of lunar soil to be deduced. [PERSON] et al. [2] conducted static cone penetration tests on lunar soil samples retrieved by Apollo 11 under the looestest and densest conditions. The results showed that, at the same compactness level, the penetration resistance increases with an increase in penetration depth. Moreover, the greater the compactness, the higher the penetration resistance becomes. [PERSON] et al. [3] conducted a comparative analysis of the results of static cone penetration tests at the Apollo15 lunar landing site and the physical-mechanical properties of lunar soil, and determined cohesion and internal friction angle. The Luna 13 mission utilized a fuel-powered engine to insert a conical probe into the lunar soil to measure its mechanical property parameters. Subsequently, the physical and mechanical properties of the soil were calibrated using lunar soil simulants [4]. [PERSON] et al. [5] employed a centrifuge to simulate gravitational variations, aiming to investigate the changes in the cone tip resistance of lunar soil simulants. The experimental results demonstrated that, under diverse moderate-gravity conditions, the normalized cone tip resistance initially ascended to a peak value and subsequently declined to a constant value with the increase in penetration depth. Additionally, both the peak and the stable values of the normalized cone tip resistance exhibited a decreasing trend with the augmentation of gravitational acceleration. [PERSON] et al. [6] investigated the penetration resistance of the CUMT-1 lunar soil simulant under magnetically simulated lunar gravity conditions. They analyzed the impacts of the low lunar gravity and the special characteristics of lunar soil through a series of micro-penetration tests. The results indicated that an increase in gravity led to a non-linear increase in penetration resistance, which was more pronounced at low relative densities. [PERSON] et al. [7] conducted research on the impacts of porosity and vertical stress on cone tip resistance and lateral frictional resistance in both the Earth and Moon environments. The results demonstrated that cone tip resistance and lateral frictional resistance increase with the increase in compactness in both environments. Moreover, as the vertical stress increases, the influence of compactness becomes more prominent. [PERSON] et al. [8; 9; 10] designed an experimental device for a static cone penetration model box. They conducted static cone penetration tests on the TJ-1 lunar soil simulant at three different penetration angles to explore its mechanical properties. The results showed penetration-shear failure in the lunar soil simulant in the surface layer of the foundation. The penetration resistance increased with an increase in penetration depth under the three penetration angles, and the penetration resistance increased with an increase in penetration angle at the same penetration depth. Through a comparative analysis of static cone penetration tests and static load tests, an empirical formula suitable for calculating the bearing capacity of lunar soil was explored, and the relationship between plate load tests and static cone penetration tests was established. Subsequently, this relationship was verified through large-scale outdoor tests.