# Research on the Compactness of Lunar Soil Simulant Based on Static Cone Penetration Test
## 1 Introduction
The above-mentioned experiments took the differences between the environments of the Earth and Moon into account and carried out penetration tests under various conditions considering factors such as gravity, depth, and penetration angle. Numerical simulations have been widely applied to static cone penetration tests to simulate the lunar environment. [PERSON] et al. [11] utilized the discrete element software PFC2D 5.0 to conduct a comparative analysis of static cone penetration tests under the gravitational fields of the Earth and the Moon, aiming to investigate the differences in the results of static cone penetration tests under high- and low-gravity fields. [PERSON] et al. [12] analyzed the impacts of model size, relative density, confining pressure stress, and boundary conditions on cone tip resistance through the discrete element simulation of static cone penetration tests and established the relationship between cone tip resistance and critical state parameters. [PERSON] et al. [13] performed numerical simulations of triaxial shear tests and static cone penetration tests in the lunar environment using the three-dimensional discrete element method. They proposed a model for calculating the shear strength index of lunar soil based on normalized cone tip resistance, making use of the results of triaxial and cone penetration test simulations and referring to the empirical formula derived from ground cone penetration test data. [PERSON] et al. [14] developed a model coupling finite and discrete element methods for static cone penetration and discussed the effects of penetration velocity, penetration depth, and cone tip angle on cone tip resistance. [PERSON] al. [15] explored the influence of different particle shapes and size distributions in the discrete element model on cone tip resistance and lateral frictional resistance in static cone penetration simulations. They compared the simulation results with those of static cone penetration tests on JSC-1A lunar soil simulant, concluding that particle size and shape distribution are the two most important factors affecting the strength of lunar soil. However, the established studies lack consideration of the inhomogeneity of lunar soil compactness at different depths. Therefore, it is important to prepare lunar soil simulants with varying compactness states in the depth direction and conduct research via static cone penetration tests. In this way, a model of the relationship between the compactness of lunar soil and the cone tip resistance in static cone penetration tests can be established, which is crucial for determining the compactness profile of lunar soil in the depth direction. In this paper, layered compaction barrels are used to conduct static cone penetration tests of a lunar soil simulant under different compactness. Due to the effect of gravity, there will be a phenomenon during the vibration and compaction process where the compactness of the lunar soil simulant in the lower layer is high and that in the upper layer is low. However, the true compactness of the lunar soil simulant at different depths can be obtained through stratified measurement, accounting for the influence of variations in compactness. Then, the static cone penetration test results can be associated with the real compactness of the lunar soil simulant at different depths, allowing a model of the relationship between cone tip resistance and lunar soil simulant compactness to be obtained and thus providing a reference for in situ test results of construction on the lunar surface.