Soil moisture detection research, which influences crop growth, land use, and soil erosion, is receiving significant attention. This study proposes a nondestructive, integrated ultrawideband (UWB)-based framework for soil moisture measurement and prediction. The method utilizes a UWB-loaded unmanned aerial vehicle (UAV) to gather radar echo data, circumventing soil damage issues inherent in current research and equipment. We first employ time-frequency analysis methods to convert the echo signals into 2-D spectrograms, constructing datasets labeled with soil moisture. Then, a trained neural network is used to predict the soil moisture at single point. Additionally, a novel interpolation method is proposed to enhance prediction accuracy (ACC) for the ridge-furrow structure of farmland. The experimental results demonstrate that the proposed algorithm achieves a soil moisture measurement ACC of 98% in both vegetated and nonvegetated conditions, indicating strong robustness. In terms of moisture distribution prediction, the mean squared error (mse) of soil moisture spatial distribution prediction is reduced by 42% compared to traditional methods. Therefore, this system provides technical support for efficient, large-scale, and nondestructive soil information collection.

Foundation elements with rough (textured) surfaces mobilize larger interface shear resistance than ones with conventional smooth or random rough surfaces when sheared against soils under monotonic loading. The overall performance of foundation elements such as piles supporting offshore wind turbines, suction caissons supporting tidal energy converters, soil nails, and soil anchors installed in cohesive soils could be enhanced through utilizing rough (textured) surfaces to resist applied static and/or cyclic loading. This paper describes the shear behavior of smooth and rough (textured) surfaces in kaolinite clay and kaolinite clay-sand mixture soils under static and cyclic axial loading. The experimental investigation presented herein consists of a series of interface shear tests performed on 3D printed rough (textured) surfaces and a 3D printed smooth reference surface utilizing the Cyclic Interface Shear Test system. The paper includes a description of the interface testing system components, cohesive soil specimens' preparation procedure, smooth and rough (textured) surfaces details, testing procedure, and results of static and cyclic tests. Test results indicate that kaolinite clay-sand mixture soil mobilized larger static and post-cyclic interface shear resistance and volume contraction relative to kaolinite clay soil when sheared against the smooth reference surface. When tested against rough (textured) surfaces with variable asperity height, larger shear resistance was mobilized and larger soil dilation greater than that mobilized by the reference untextured surface in both soils. The results also indicate rough (textured) surfaces exhibited a prevalent frictional anisotropy increases with asperity angle and height in cohesive soils, the surfaces mobilized larger shear resistance and volume change in one direction (i.e., against the asperity right-angled side) than the other direction (i.e., along the asperity inclined side).

To assess the stability of coral sand foundation in complex environments, the undrained monotonic and cyclic shear tests were conducted in the laboratory. The test results indicate that the coral sand exhibits pronounced inherent anisotropy in the vertical direction. Under complex consolidation conditions, significant stress-induced anisotropy can also be observed. With increasing generalized shear strain (gamma g), both the generalized monotonic and cyclic shear modulus (Ggm, Ggd) exhibit a decreasing trend irrespective of consolidation ratio (kc) and inclinations of major principal stress (alpha c). Additionally, a strong linear relationship is evident between Ggm and Ggd, suggesting a consistent reduction pattern of Gg for various loading modes. The investigation on the inclination of the failure line (phi FL) for monotonic and cyclic shear is also conducted. The test results show that consolidation conditions have minimal influence on phi FL during monotonic shear, but exert a significant impact on phi FL during cyclic shear. A novel index called the consolidation parameter (eta) is proposed to quantitatively assess the relationship between kc, alpha c and phi FL. The average values of phi FL for cyclic shear increase with increasing eta, indicating the non-failure zone of coral sand during undrained cyclic shear will shrink with higher values of kc and alpha c.

High circular polarization ratio (CPR) characteristics were found in permanently shaded regions (PSRs) near the lunar poles. High CPR was regarded as a water ice index. The compact-polarimetric (CP) miniature radio frequency (Mini-RF) radar transmits left-circularly polarized signals and receives horizontally polarized ($S_{\text {HL}}$ ) and vertically-polarized ($S_{\text {VL}}$ ) echoes from the lunar surface. Statistics of the CPR data show its relations with the relative phase ($\delta$ ) between $S_{\text {HL}} $ and $S_{\text {VL}} $ and the degree of polarization ($m$ ) but few interpretations were provided. The average CPR data reach the maximum and minimum at $\delta =\pm 90{\circ }$ , respectively. As $m$ becomes very small, the CPR approaches 1. It has been found that CPR is also affected by surface roughness and incidence angle of radar waves. The CPR is now expressed in CP mode to explain the Mini-RF observation. Full-polarimetric radar echoes and CP parameters of the lunar surface are numerically simulated using the bidirectional analytic ray-tracing method. Single-bounce and multiple-bounce scattering components are included in the simulation. Radar images of the lunar crater are simulated with the digital elevation model (DEM) data. The $H-\alpha $ decomposition derived from the full-polarimetric simulation is presented to analyze $\delta $ and $m$ . Simulated radar images with different surface roughness are analyzed statistically to study the functional dependences of $\delta $ , ${m}$ , and CPR on incidence angle and roughness. Relationships among $\delta $ , $m$ , and CPR are used to analyze the effects of incidence angle, roughness, TiO2, and rock abundance on the scattering components. The CPR, $m$ , and $\delta $ of PSR craters of different ages are compared with those of nonpolar craters. The results indicate that the CPR, $m$ , and $\delta $ are unlikely to be unambiguous evidence of water ice.

Direct sampling has never been performed in the permanently shadowed regions (PSRs) of lunar poles up to now. In the Chinese Chang'e-7 (CE-7) mission, a mini-flyer will fly from the lander in a solar illuminated region at the lunar south polar region to the nearby PSRs to collect samples for analysis. In this letter, four potential craters of the lunar south pole, including Shackleton, Shoemaker, de Gerlache, and Slater are discussed for this proposal. Design principles of the landing site, sampling site, and flight route are presented. The local surface slopes are calculated using a digital elevation model (DEM) to select a flat area as a potential landing site, which should allow ample time for solar illumination to support the rover from the lander and allow the flyer to reach the neighboring PSRs. Mini-RF data are applied for further validation of the flat landing and sampling sites, particularly for some rocky rough surfaces that are not identified in DEM and optical images of PSRs. The craters de Gerlache and Slater are found to be suitable for further analysis when high-resolution synthetic aperture radar (SAR) data are acquired by the new polarimetric SAR carried by CE-7.

Circular polarization ratio (CPR) was regarded as an important index for water ice existence in permanently shadowed region (PSR) of the Moon poles. However, some studies have intuitively described that the double bounce scattering caused by dihedral structure of stone facets may yield high CPR as well. In this paper, a numerical model of the Moon cratered rough surface with volumetric scatterers, e.g. rock-stones, is developed. The bidirectional analytic ray tracing (BART) method is applied to numerically solve high-order scattering of lunar rough surface and volumetric rock-stones. The lunar surface is modeled by Digital Elevation Model (DEM) data from Lunar Reconnaissance Orbiter (LRO) Lunar Orbiter Laser Altimeter (LOLA). It is the first numerical approach to quantitatively analyze how the cratered surface topography, discrete stones and radar local incidence etc. affect and enhance the CPR.

Dielectric inversion of lunar permanently shadowed region (PSR) of moon poles has been studied for estimation of possible water-ice content. The Campbell model was directly applied to mini-SAR data for inversion on the Hermite-A crater region. However, this letter presents quantitative analysis that the lunar surface topography, i.e., surface roughness and slopes, and underlying dielectric media, and so on, can significantly affect this inversion. The model is actually degenerated into a half-space model without topographic account. This letter presents a two-layer model of Kirchhoff-approximation surface/small perturbation approximation subsurface to take account of all these topographic factors for PSR dielectric inversion.