A non-destructive prediction method for shear strength parameters of real lunar soil
By combining funnel tests, drum tests, and numerical simulations, the problem of measurement error in the shear strength parameters of real lunar soil was solved, and accurate shear strength prediction was achieved, providing a reliable safety guarantee for lunar mining.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- CHINA UNIV OF MINING & TECH (BEIJING)
- Filing Date
- 2026-03-20
- Publication Date
- 2026-06-19
AI Technical Summary
Current technology relies on Earth-simulated lunar soil for shear strength studies, which leads to significant errors in the measurement of actual lunar soil shear strength parameters and makes it impossible to accurately predict the safety and stability of lunar mining.
The static and dynamic angles of repose of real lunar regolith were obtained through funnel and drum experiments. The particle shape and roughness were measured by combining SEM scanning electron microscopy, 3D CT scanning and 3D white light interferometry. Lunar regolith particles were reproduced in numerical simulation using rblock elements, and a numerical model was constructed to predict shear strength parameters.
This method enables non-destructive prediction of real lunar soil shear strength parameters, improves the accuracy of numerical simulation, reduces errors, and ensures the safety and stability of lunar mining.
Smart Images
Figure CN122242019A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of lunar mining technology, and in particular to a non-destructive method for predicting the shear strength parameters of real lunar soil. Background Technology
[0002] As the closest celestial body to Earth, the Moon is rich in mineral resources, including silicates, oxides, sulfides, and natural metals, such as new minerals not found on Earth, such as clinopyroxene (CaFe6(SiO3)7) and zircon (ZrSiO2).
[0003] The shear strength properties of lunar regolith are a key mechanical indicator affecting the stability and safety of lunar surface engineering. However, due to the extreme scarcity of real lunar regolith samples, most existing studies rely on Earth-simulated lunar regolith to approximate its physical and mechanical behavior. Since there are certain differences between the two in terms of shear strength properties, conclusions drawn entirely from simulated lunar regolith may contain significant errors.
[0004] Therefore, providing a non-destructive prediction method for real lunar soil shear strength parameters to overcome the difficulties in existing technologies is a problem that urgently needs to be solved by those skilled in the art. Summary of the Invention
[0005] In view of this, the present invention provides a non-destructive prediction method for the shear strength parameters of real lunar soil, which not only ensures the use of real lunar soil as is, but also uses numerical simulation to predict its shear strength parameters, providing a new means for subsequent lunar mining research.
[0006] To achieve the above objectives, the present invention adopts the following technical solution: A non-destructive prediction method for real lunar soil shear strength parameters includes the following steps: Lunar soil samples were obtained, and the static angle of repose of the lunar soil was determined by the funnel test, while the dynamic angle of repose of the lunar soil was obtained by the roller test. Typical particles of different sphericity were selected from lunar soil samples by SEM scanning electron microscopy. Three-dimensional particle data were obtained by scanning the typical particles with three-dimensional CT. Two-dimensional morphological features of the particles were obtained by the subdivision method. The particle shape data were simulated in numerical simulation by combining rblock elements to reproduce the real lunar soil particle shape in two dimensions. The surface roughness of typical particles was measured using a 3D white light interferometer, and the sliding friction coefficient of typical particles was obtained. The particle size distribution of lunar soil samples was measured using a particle size analyzer to obtain particle size distribution curves; A numerical model is constructed based on real lunar soil particles, typical particle sliding friction coefficients, and particle size distribution curves in a two-dimensional angle, combined with a specific contact model. Based on the constructed numerical model, simulated static and dynamic angles of repose are obtained. The simulated static and dynamic angles of repose of lunar soil are compared and optimized to obtain a reliable set of parameters. Based on this set of parameters, a numerical model for simulating direct shear of lunar soil is established. The shear strength parameters of real lunar soil in the test data were predicted using a numerical model of direct shear of simulated lunar soil.
[0007] Optionally, obtaining the static angle of repose of the lunar regolith includes: A real lunar soil cone was obtained by using a glass funnel and a glass rod to conduct a real lunar soil funnel experiment on the lunar soil sample. Linear fitting is performed on the cone profile by connecting the highest and lowest points of the cone profile, and the angles of the slopes on the left and right sides of each cross section of the cone are calculated and fitted respectively. The average of the results from the two fitting methods is taken as the static rest angle.
[0008] Optionally, obtaining the dynamic repose angle of the lunar regolith includes: Lunar soil samples were stored in a vacuum chamber, which was then fixed to a roller testing machine for rotation. The slope angle at the instant of separation between lunar soil and the vacuum tank wall is defined as the upper angle of repose, and the slope angle that finally stabilizes after separation is defined as the lower angle of repose. Let the average of the upper and lower repose angles be taken as the dynamic repose angle.
[0009] Optionally, obtaining a two-dimensional shape includes: Import the 3D scanned particle shape into Rhino software for 3D subdivision to obtain the 2D shape; Two-dimensional shapes are filled with triangular facets, and the actual two-dimensional shapes of lunar soil particles are constructed based on the filled shapes.
[0010] Optionally, obtain the typical particle sliding friction coefficient. The expression is: , in, S q This refers to particle roughness.
[0011] Optionally, the contact models include rblock-rblock contact simulation and rblock-facet contact simulation; The rblock-rblock contact simulation uses the Arrlinear model with the rolling resistance rrfric set to 0. The maximum attractive force and range of the Adhesive part of the Arrlinear model are used to linearly approximate the van der Waals force between real lunar soil particles. The sliding friction coefficient of particles with different sphericity is set by the user. If the simulation effect is not good, the rolling resistance rrfric is appropriately increased to make the simulated angle of repose close to the angle of repose of the lunar soil laboratory test. The rblock-facet contact simulation uses the rrlinear model.
[0012] As can be seen from the above technical solution, compared with the prior art, the present invention provides a non-destructive prediction method for real lunar soil shear strength parameters, which has the following beneficial effects: 1) The indirect testing of shear strength parameters (internal friction angle, cohesion) in the indoor test and the acquisition of various parameters in the numerical simulation of the present invention are all based on real lunar soil, which solves the error caused by the current method of obtaining shear strength parameters by simulating lunar soil instead of real lunar soil; 2) In the numerical simulation of the present invention, the main influencing factors of soil shear strength parameters such as the shape, roughness, and particle size distribution of real lunar soil particles are considered in a coordinated manner, and the rationality of the selection of numerical model parameters is verified by the indoor test results of the angle of repose of real lunar soil, ensuring the accuracy of numerical simulation; 3) After processing the three-dimensional shape of real lunar soil particles with Rhino software, the present invention combines the rblock unit in PFC to achieve perfect reproduction of real lunar soil particles; compared with the traditional simulation method of clump and cluster units, the particle shape characterization accuracy of this method is higher. Attached Figure Description
[0013] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the provided drawings without creative effort.
[0014] Figure 1 This is a flowchart of a non-destructive prediction method for real lunar soil shear strength parameters disclosed in this invention; Figure 2 This is a schematic diagram of the method for predicting real lunar soil shear strength parameters disclosed in this invention. Figure 3 This is a schematic diagram of the indoor angle of repose test of real lunar soil disclosed in this invention; Figure 4 This is a schematic diagram illustrating the acquisition of real lunar soil particle shape characteristics as disclosed in this invention; Figure 5This is a schematic diagram illustrating the acquisition of real lunar soil particle roughness as disclosed in this invention; Figure 6 This is a partial real lunar soil particle size distribution curve disclosed in this invention; Figure 7 This is a schematic diagram of the numerical simulation lunar soil contact model based on real lunar soil disclosed in this invention; Figure 8 This is a prediction diagram of the actual lunar soil shear strength parameters disclosed in an embodiment of the present invention. Detailed Implementation
[0015] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.
[0016] Reference Figure 1 and Figure 2 As shown, this invention discloses a non-destructive prediction method for real lunar soil shear strength parameters, comprising the following steps: Lunar soil samples were obtained, and the static angle of repose of the lunar soil was determined by the funnel test, while the dynamic angle of repose of the lunar soil was obtained by the roller test. Typical particles of different sphericity were selected from lunar soil samples by SEM scanning electron microscopy. Three-dimensional particle data were obtained by scanning the typical particles with three-dimensional CT. Two-dimensional morphological features of the particles were obtained by the subdivision method. The particle shape data were simulated in numerical simulation by combining rblock elements to reproduce the real lunar soil particle shape in two dimensions. The surface roughness of typical particles was measured using a 3D white light interferometer, and the sliding friction coefficient of typical particles was obtained. The particle size distribution of lunar soil samples was measured using a particle size analyzer to obtain particle size distribution curves; A numerical model is constructed based on real lunar soil particles, typical particle sliding friction coefficients, and particle size distribution curves in a two-dimensional angle, combined with a specific contact model. Based on the constructed numerical model, simulated static and dynamic angles of repose are obtained. The simulated static and dynamic angles of repose of lunar soil are compared and optimized to obtain a reliable set of parameters. Based on this set of parameters, a numerical model for simulating direct shear of lunar soil is established. The shear strength parameters of real lunar soil in the test data were predicted using a numerical model of direct shear of simulated lunar soil.
[0017] Furthermore, refer to Figure 3 As shown, obtaining the static angle of repose of the lunar regolith includes: To avoid the influence of electrostatic forces on the properties of real lunar soil, a real lunar soil funnel test was conducted on the lunar soil sample using a glass funnel and a glass rod. The entire test process was recorded using a high-speed camera. Finally, after the funnel test was completed, a real lunar soil cone was obtained, and the outline of the real lunar soil cone was photographed from different angles. Linear fitting is performed on the cone profile by connecting the highest and lowest points of the cone profile, and the angles of the slopes on the left and right sides of each cross section of the cone are calculated and fitted respectively. The average of the results from the two fitting methods is taken as the static rest angle.
[0018] Furthermore, obtaining the dynamic repose angle of the lunar regolith includes: Lunar soil samples were stored in a vacuum chamber, which was then fixed to a roller test machine and rotated clockwise at a speed of 0.1 rad / s. The particle flow process was recorded using a high-speed camera. The slope angle at the instant of separation between lunar soil and the vacuum tank wall is defined as the upper angle of repose, and the slope angle that finally stabilizes after separation is defined as the lower angle of repose. Let the average of the upper and lower angles of repose be taken as the dynamic angle of repose.
[0019] Furthermore, the dynamic and static angles of repose were measured repeatedly, and the average value of the multiple tests was taken as the dynamic and static angles of repose obtained in the experiment to reduce experimental error.
[0020] Furthermore, refer to Figure 4 As shown, obtaining a two-dimensional shape includes: Representative particles of different shapes were found using SEM (scanning electron microscopy). Then, these particles were scanned using 3D CT technology to obtain their 3D particle shapes and calculate the sphericity value of each particle, classifying the particles according to sphericity. Import the 3D scanned particle shape into Rhino software for 3D subdivision to obtain the 2D shape; Two-dimensional shapes are filled with triangular facets, and the filled shape file is exported as an STL file. In PFC, the STL format shape file is used to construct realistic two-dimensional shapes of lunar regolith particles using its built-in rblock units.
[0021] Specifically, the rblock unit significantly outperforms the clump and cluster units in simulating particle shapes, and the particle shapes constructed by the rblock unit are highly similar to the real particle shapes.
[0022] Furthermore, the sliding friction coefficient of typical particles was obtained. The expression is: , in, S q For particle roughness, the expression is: , in, u To measure the number of data points, It is the elevation of the i-th data point relative to the base plane.
[0023] Furthermore, in numerical modeling, the range command is used to apply different coefficients of sliding friction to particles with different sphericity. , among which Figure 5 As shown, combining the roughness between particles with real lunar soil particles of different sphericities reflects both the shape of real lunar soil particles and the surface roughness of the lunar soil particles.
[0024] Furthermore, the particle size distribution of the actual lunar soil was measured using a particle size analyzer to obtain the particle size distribution gradation curve of the actual lunar soil, such as... Figure 6 As shown; since the particle size distribution curves of real lunar soil are quite extensive, establishing a numerical model based on the real particle size distribution curves may result in very slow calculations. Therefore, in numerical simulations, it is necessary to simplify the particle size distribution curves of real lunar soil to a certain extent, so as to ensure the computational efficiency of numerical simulations without changing the basic principles of the particle size distribution of real lunar soil.
[0025] Based on fundamental knowledge of soil mechanics and a review of relevant literature, for general mechanics and engineering problems, it is possible to ensure the median particle size. d 50 Without altering the particle size distribution, computational efficiency can be improved. The number of particles in the two-dimensional simulation unit test must be greater than 2000, and the number of particles in the three-dimensional simulation unit test must be greater than 40000.
[0026] Furthermore, refer to Figure 7 As shown, the contact models include rblock-rblock contact simulation and rblock-facet contact simulation; The rblock-rblock contact simulation uses the Arrlinear model with the rolling resistance rrfric set to 0. The maximum attractive force and range of the Adhesive part of the Arrlinear model are used to linearly approximate the van der Waals force between real lunar soil particles. The sliding friction coefficient of particles with different sphericity is set by the user. If the simulation effect is not good, the rolling resistance rrfric is appropriately increased to make the simulated angle of repose close to the angle of repose of the lunar soil laboratory test. The rblock-facet contact simulation uses the rrlinear model.
[0027] Furthermore, a numerical model for the roller and funnel experiment was established, with the gravity field of the numerical model being the Earth's gravity field of 9.81 m / s². 2 An angular velocity of 0.1 rad / s was applied to the drum sample, and the funnel test was a free fall under a gravitational field. Referring to the calculation methods of dynamic and static angles of repose in the laboratory test, the dynamic and static angles of repose of the numerical simulation of lunar soil were compared and calibrated with the laboratory test results to ensure that the angle difference between the two was <2°, thus obtaining a reliable set of numerical simulation parameters. Based on this set of parameters, a numerical model for simulating direct shear of lunar soil was constructed.
[0028] In one specific embodiment, refer to Figure 8 As shown, direct shear tests were conducted on the lunar soil numerical model under different confining pressures (due to the special environmental conditions of the moon, the confining pressure here is mainly low confining pressure). The shear stress-displacement curves under different confining pressures were recorded. The shear strength parameters (cohesion and internal friction angle) of the real lunar soil were predicted in the numerical simulation using the Mohr-Coulomb criterion.
[0029] This application can not only be used to predict the shear strength parameters of real lunar soil, but can also be extended to other lunar soils, precious soils, and other soil types whose strength parameters are difficult to obtain through direct shear tests. It can accurately obtain their shear strength parameters without damaging the soil's strength properties. It can be understood and implemented by those skilled in the art without any inventive effort.
[0030] The above description of the disclosed embodiments enables those skilled in the art to make or use the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.
Claims
1. A non-destructive prediction method for real lunar soil shear strength parameters, characterized in that, Includes the following steps: Lunar soil samples were obtained, and the static angle of repose of the lunar soil was determined by the funnel test, while the dynamic angle of repose of the lunar soil was obtained by the roller test. Typical particles of different sphericity were selected from lunar soil samples by SEM scanning electron microscopy. Three-dimensional particle data were obtained by scanning the typical particles with three-dimensional CT. Two-dimensional morphological features of the particles were obtained by the subdivision method. The particle shape data were simulated in numerical simulation by combining rblock elements to reproduce the real lunar soil particle shape in two dimensions. The surface roughness of typical particles was measured using a 3D white light interferometer, and the sliding friction coefficient of typical particles was obtained. The particle size distribution of lunar soil samples was measured using a particle size analyzer to obtain particle size distribution curves; A numerical model is constructed based on real lunar soil particles, typical particle sliding friction coefficients, and particle size distribution curves in a two-dimensional angle, combined with a specific contact model. Based on the constructed numerical model, simulated static and dynamic angles of repose are obtained. The simulated static and dynamic angles of repose of lunar soil are compared and optimized to obtain a reliable set of parameters. Based on this set of parameters, a numerical model for simulating direct shear of lunar soil is established. The shear strength parameters of real lunar soil in the test data were predicted using a numerical model of direct shear of simulated lunar soil.
2. The non-destructive prediction method for real lunar soil shear strength parameters according to claim 1, characterized in that, Obtaining the static angle of repose of lunar regolith includes: A real lunar soil cone was obtained by using a glass funnel and a glass rod to conduct a real lunar soil funnel experiment on the lunar soil sample. Linear fitting is performed on the cone profile by connecting the highest and lowest points of the cone profile, and the angles of the slopes on the left and right sides of each cross section of the cone are calculated and fitted respectively. The average of the results from the two fitting methods is taken as the static rest angle.
3. The non-destructive prediction method for real lunar soil shear strength parameters according to claim 1, characterized in that, Obtaining the dynamic repose angle of lunar soil includes: Lunar soil samples were stored in a vacuum chamber, which was then fixed to a roller testing machine for rotation. The slope angle at the instant of separation between lunar soil and the vacuum tank wall is defined as the upper angle of repose, and the slope angle that finally stabilizes after separation is defined as the lower angle of repose. Let the average of the upper and lower repose angles be taken as the dynamic repose angle.
4. The non-destructive prediction method for real lunar soil shear strength parameters according to claim 1, characterized in that, Obtaining two-dimensional shapes includes: Import the 3D scanned particle shape into Rhino software for 3D subdivision to obtain the 2D shape; Two-dimensional shapes are filled with triangular facets, and the actual two-dimensional shapes of lunar soil particles are constructed based on the filled shapes.
5. The non-destructive prediction method for real lunar soil shear strength parameters according to claim 1, characterized in that, Obtain the typical particle sliding friction coefficient The expression is: ， in, S q This refers to particle roughness.
6. The non-destructive prediction method for real lunar soil shear strength parameters according to claim 1, characterized in that, Contact models include rblock-rblock contact simulation and rblock-facet contact simulation; The rblock-rblock contact simulation uses the Arrlinear model with the rolling resistance rrfric set to 0. The maximum attractive force and range of the Adhesive part of the Arrlinear model are used to linearly approximate the van der Waals force between real lunar soil particles. The sliding friction coefficient of particles with different sphericity is set by the user. If the simulation effect is not good, the rolling resistance rrfric is appropriately increased to make the simulated angle of repose close to the angle of repose of the lunar soil laboratory test. The rblock-facet contact simulation uses the rrlinear model.