Surficial water ice has been detected in the permanently shaded regions (PSRs) near the lunar poles. Water ice can be detected by its diagnostic absorption features of ice at 1.0, 1.25, 1.5, and 2.0 mu m, as well as high reflectance in the VIS region. However, the effects of particle size and shape, ice abundance, and phase angle on the VNIR spectra of ice mixtures remain poorly understood, posing a challenge for detections of water ice on the lunar surface. In this study, we measured the VNIR spectra of pure water ice and mixtures of water ice and a lunar highland regolith simulant (HRS). We investigated the effects of particle size of ice (0-250 mu m), particle shape of ice (angular vs. spherical), phase angle (0-105 degrees), and ice abundance (0-50 wt%) on the VNIR spectra of water ice and HRS mixtures from 350 to 2500 nm. Our results show that coarser ice particles exhibit stronger NIR absorptions and lower VIS reflectance, attributable to increased photon absorptions due to longer optical pathlengths. Similarly, the longer optical pathlengths of spherical particles relative to angular ones result in lower VIS reflectance. The forward scattering nature of water ice leads to increased VIS reflectance at high phase angles (>90 degrees), suggesting that high phase angles are optimal for lunar water ice detection. Phase angles have a negligible effect on the strength of the NIR absorptions of ice, especially when ice is present at low ice abundances (<20 wt%) in intimate mixtures with the HRS. Lastly, our findings suggest that the NIR absorptions near 1.25, 1.5, and 2.0 mu m rapidly deepen at very low ice concentrations (0-5 wt%). We also find a linear relationship between VIS reflectance and ice content in intimate mixtures with a HRS containing 0-50 wt% ice. The findings of this study offer a detailed framework for detecting and analyzing water ice on the lunar surface via VNIR spectroscopy.

In slurry shield tunneling, the stability of tunnel face is closely related to the filter cake. The cutting of the cutterhead has negative impact on the formation of filter cake. This study focuses on the formation time of dynamic filter cake considering the filtration effect and rotation of cutterhead. Filtration effect is the key factor for slurry infiltration. A multilayer slurry infiltration experiment system is designed to investigate the variation of filtrate rheological property in infiltration process. Slurry mass concentration CL, soil permeability coefficient k, the particle diameter ratio between soil equivalent grain size and representative diameter of slurry particles d(10)/D-85 are selected as independent design variables to fit the computational formula of filtration coefficient. Based on the relative relation between the mass of deposited particles in soil pores and infiltration time, a mathematical model for calculating the formation time of dynamic filter cake is proposed by combining the formation criteria and formation rate of external filter cake. The accuracy of the proposed model is verified through existing experiment data. Analysis results show that filtration coefficient is positively correlated with slurry mass concentration, while negatively correlated with the soil permeability coefficient and the particle diameter ratio between soil and slurry. As infiltration distance increases, the adsorption capacity of soil skeleton to slurry particles gradually decreases. The formation time of external filter cake is significantly lower than internal filter cake and the ratio is approximately 3.9. Under the dynamic cutting of the cutterhead, the formation time is positively associated with the rotation speed of cutter head, while negatively with the phase angle difference between adjacent cutter arm. The formation rate of external filter cake is greater than 98% when d(10)/D-85 <= 6.1. Properly increasing the content or decreasing the diameter size of solid-phase particles in slurry can promote the formation of filter cake.