An experimental device and method for calibrating the accuracy of photogrammetric measurement of rock content in soil-rock mixtures

Abstract

The present invention relates to an experimental device and method for calibrating the accuracy of photogrammetric measurement of the stone content of a soil-rock mixture. The device comprises a motor, a rotating shaft, a transparent model box, a bracket, a high-definition camera, and a base. The bracket is mounted on the base, the motor is fixed to the bracket, the motor is in transmission connection with the rotating shaft, the rotating shaft passes through the transparent model box and is mounted on the bracket. The transparent model box is used to hold the soil-rock mixture and rotates synchronously with the rotating shaft. The high-definition camera is located directly below the transparent model box. The present invention can change the exposed surface of the soil-rock mixture displayed at the bottom of the soil model box by rotating the model box, simulating the randomness of the stone distribution on the exposed surface of the soil-rock mixture in nature, facilitating statistical analysis of errors and obtaining reliable error statistics.

Description

Technical Field

[0001] The invention belongs to the fields of geotechnical engineering and engineering geology, and in particular relates to an experimental device and method for calibrating the accuracy of photogrammetric measurement of the stone content of a soil-rock mixture. Background Art

[0002] Soil-rock mixtures are the most common geological bodies in nature. They are composed of a mixture of soil and rock. Their mechanical properties are closely related not only to the mechanical properties of the soil but also to the rock content. Accurately assessing the mechanical parameters of soil-rock mixtures is essential for calculating the deformation and bearing capacity of soil-rock mixture foundations and the stability of soil-rock mixture landslides. Due to the large particle size of rock, conventional experimental equipment cannot directly measure their mechanical parameters. The commonly used method is to use conventional experimental equipment to measure the mechanical parameters of the soil, then determine the rock content in the soil-rock mixture. Based on the rock content and soil mechanical parameters, statistical models are used to evaluate the mechanical parameters of the soil-rock mixture. Therefore, accurately assessing the rock content is key to determining the mechanical parameters of soil-rock mixtures.

[0003] Traditional methods for assessing rock content involve sieving a defined volume of soil-rock mixture on-site to separate soil and rock fragments. The rock fragment volume is then measured and divided by the total volume of the soil-rock mixture to determine the volumetric rock content. This method requires extensive on-site excavation, which is time-consuming and labor-intensive, and can easily disrupt the stability of the existing soil-rock mixture. To avoid disturbing the existing soil-rock mixture, photography can be used to capture the exposed surface of the soil-rock mixture. Using image processing techniques, rock fragments and soil fragments can be identified in the photographs. The ratio of the rock fragment area in the image to the total photographed area is then used to determine the rock content. Although this photogrammetry method is fast and convenient, it remains unclear whether the rock content obtained from two-dimensional images accurately represents the true rock content of the soil-rock mixture in three dimensions. Summary of the Invention

[0004] The present invention addresses the problem that existing photogrammetric methods for measuring the rock content of soil-rock mixtures cannot consider the influence of three-dimensional effects and have unknown accuracy. This invention provides an experimental device and method for simulating the possible exposure states of soil-rock mixtures with different rock contents, quickly obtaining two-dimensional photographs of the exposed surface, and analyzing the accuracy of photogrammetric measurements of rock content under different rock contents, providing a reference for engineering applications and for evaluating the accuracy of photogrammetric measurements of rock content in soil-rock mixtures.

[0005] To achieve the above object, the technical solution provided by the present invention is:

[0006] An experimental device for calibrating the accuracy of photogrammetric measurement of the stone content of a soil-rock mixture comprises a motor, a rotating shaft, a transparent model box, a bracket, a high-definition camera and a base; the bracket is mounted on the base, the motor is fixed on the bracket, the motor is connected to the rotating shaft through a transmission, the rotating shaft passes through the transparent model box and is mounted on the bracket, the transparent model box is used to hold the soil-rock mixture and rotates synchronously with the rotating shaft, and the high-definition camera is located directly below the transparent model box.

[0007] An experimental method for calibrating the accuracy of photogrammetric measurement of rock content in soil-rock mixtures comprises the following steps:

[0008] Step 1: Place a soil-rock mixture with a known volume of rock content into a transparent model box, and use a high-definition camera placed on the bottom plate to take a photo of the transparent bottom surface of the model box to obtain a photo of the exposed surface of the soil-rock mixture;

[0009] Step 2: The motor drives the rotating shaft to rotate the transparent model box on the bracket for several turns. After the rotation stops, the high-definition camera takes another photo of the bottom of the model box to obtain a photo of the exposed surface of the soil-rock mixture.

[0010] Step 3: Repeat step 2 to obtain multiple photos of the exposed surface of the soil-rock mixture at the bottom of the transparent model box;

[0011] Step 4: Process the obtained photos to obtain the area occupied by the stone blocks.

[0012] Step 5: Obtain the mean value, standard deviation and distribution law of the error through error analysis.

[0013] Step 6: Repeat steps 1 to 5 for soil-rock mixtures with different rock contents to obtain the corresponding mean value, standard deviation and distribution law of the error.

[0014] Preferably, in step 2, the transparent model box rotates 3-8 times and then stops.

[0015] Preferably, in step 3, the process of step 2 is repeated 30-50 times.

[0016] Preferably, in step 4, the specific steps of image processing include:

[0017] Step 4.1: De-noise the obtained image using a mean filter;

[0018] Step 4.2: Use the weighted average method to grayscale the denoised image and convert the RGB color image into a grayscale image;

[0019] Step 4.3: Use a Gaussian filter to denoise the grayscale image and eliminate the noise in the grayscale image;

[0020] Step 4.4: Use threshold binarization to set the grayscale value of the part with grayscale value greater than the threshold to 255, which is white, and the grayscale value of the part with grayscale value less than the threshold to 0, which is black. Gray and white are used to distinguish between blocks of stone and soil.

[0021] Preferably, in step 5, the specific process of error analysis is to divide the area occupied by the block of stone by the exposed surface area captured in the photo to obtain the calculated stone content corresponding to each photo, and the difference between the calculated stone content and the actual stone content of the soil-rock mixture.

[0022] Beneficial effects of the present invention:

[0023] 1. Due to the design of the experimental device of the present invention, the exposed surface of the soil-rock mixture displayed at the bottom of the soil model box can be changed by rotating the model box, simulating the randomness of the distribution of blocks on the exposed surface of the soil-rock mixture in nature, which is conducive to the statistical analysis of errors and the acquisition of reliable error statistical data.

[0024] 2. Since the present invention uses a high-definition camera to obtain pictures, the sampling efficiency is high, and pictures can be quickly obtained after each rotation of the model box, effectively improving the efficiency of experiments and data acquisition.

[0025] 3. Due to the accuracy determination method proposed in the present invention, high-definition camera photos can be obtained in real time, and the stone content can be quickly calculated. The mean value, standard deviation and distribution law of the error under the stone content can be obtained using statistical methods.

[0026] 4. The present invention provides reliable data support for the photogrammetry method to determine the stone content of soil-rock mixture, which is conducive to improving the accuracy of photogrammetry measurement of stone content. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 It is a structural schematic diagram of the present invention; DETAILED DESCRIPTION

[0028] In order to further understand the content of the present invention, the present invention is described in detail with reference to the examples. The following examples are used to illustrate the present invention but are not used to limit the scope of the present invention.

[0029] like Figure 1 As shown, this embodiment relates to an experimental device for calibrating the accuracy of photogrammetric measurement of the stone content of a soil-rock mixture, which includes a motor 1, a rotating shaft 2, a transparent model box 3, a bracket 4, a high-definition camera 5 and a base 7; the bracket 4 is installed on the base 7, the motor 1 is fixed on the bracket 4, the motor 1 is connected to the rotating shaft 2 by transmission, the rotating shaft 2 passes through the transparent model box 3 and is mounted on the bracket 4, the transparent model box 3 is used to hold the soil-rock mixture 6 and rotates synchronously with the rotating shaft 2, and the high-definition camera 5 is arranged directly below the transparent model box 3 for taking high-definition photos of the transparent model box 3.

[0030] Based on the above experimental device for calibrating the accuracy of photogrammetric measurement of the rock content of a soil-rock mixture, this embodiment further relates to an experimental method, which specifically includes the following steps:

[0031] Step 1: Place a soil-rock mixture with a known volume of rock content into a transparent model box, and use a high-definition camera placed on the bottom plate to take a photo of the transparent bottom surface of the transparent model box to obtain a photo of the exposed surface of the soil-rock mixture.

[0032] Step 2: The motor drives the rotating shaft to rotate the transparent model box on the bracket for 3 circles. After the rotation stops, the high-definition camera takes a picture of the bottom surface of the transparent model box again to obtain a picture of the exposed surface of the soil-rock mixture.

[0033] The process of step 3 and step 2 was repeated 30 times to obtain 30 photos of the exposed surface of the soil-rock mixture at the bottom of the transparent model box.

[0034] Step 4: Use an image processing program to process the 30 photos of the exposed surface of the soil-rock mixture in the transparent model box to obtain the area occupied by the rock blocks. Image processing mainly includes the following steps: ① De-noise the obtained image using a mean filter; ② Grayscale the denoised image using a weighted average method to convert the original RGB color image into a grayscale image; ③ De-noise the grayscale image using a Gaussian filter to eliminate noise within the grayscale image; ④ Use threshold binarization to set the grayscale value of the portion with a grayscale value greater than the threshold to 255, appearing white, and the grayscale value of the portion with a grayscale value less than the threshold to 0, appearing black, using gray and white to distinguish between rock blocks and soil.

[0035] Step 5. In the error analysis program, divide the area occupied by the stone blocks by the exposed surface area captured in the photo to obtain the calculated stone content corresponding to each photo. The difference between the calculated stone content and the actual stone content of the soil-rock mixture is the error. Count the stone content errors of 30 photos, and use MATLAB to obtain the average, standard deviation, and distribution of the errors.

[0036] Step 6: Repeat the above steps for soil-rock mixtures with different stone contents to obtain the corresponding error mean, standard deviation and distribution law as a reference for practical application.

[0037] The existing experimental data are shown in Table 1:

[0038] Table 1

[0039]

[0040]

[0041] In summary, the greater the stone content of the soil-rock mixture, the smaller the error during measurement.

[0042] In practical applications, the stone content is calculated based on the photos taken. The error mean value, standard deviation and distribution law corresponding to the calculated stone content can be obtained according to the experiment to evaluate the range of the actual stone content of the soil-rock mixture and provide a reference for evaluating and calculating the mechanical parameters of the soil-rock mixture.

[0043] Although the specific embodiments of the present invention have been described in detail above, the present invention is not limited to the above embodiments. Within the scope of knowledge possessed by ordinary technicians in this field, various changes can be made without departing from the purpose of the present invention. Modifications or deformations that do not involve creative work are still within the scope of protection of the present invention.

Claims

1. An experimental method for calibrating an experimental device for photogrammetrically measuring the rock content of a soil-rock mixture, characterized in that: The experimental device includes a motor, a rotating shaft, a transparent model box, a bracket, a high-definition camera, and a base; the bracket is mounted on the base, the motor is fixed to the bracket, the motor is connected to the rotating shaft, the rotating shaft passes through the transparent model box and is mounted on the bracket, the transparent model box is used to hold a soil-rock mixture and rotates synchronously with the rotating shaft, and the high-definition camera is located directly below the transparent model box; The experimental method includes the following steps: Step 1: Place a soil-rock mixture with a known volume of rock content into a transparent model box, and use a high-definition camera placed on the bottom plate to take a photo of the transparent bottom surface of the model box to obtain a photo of the exposed surface of the soil-rock mixture; Step 2: The motor drives the rotating shaft to rotate the transparent model box on the bracket for several turns. After the rotation stops, the high-definition camera takes another photo of the bottom of the model box to obtain a photo of the exposed surface of the soil-rock mixture. Step 3: Repeat step 2 to obtain multiple photos of the exposed surface of the soil-rock mixture at the bottom of the transparent model box; Step 4: Process the obtained photos to obtain the area occupied by the stone blocks; Step 5: Obtain the mean value, standard deviation and distribution law of the error through error analysis; Step 6: Repeat steps 1 to 5 for soil-rock mixtures with different stone contents to obtain the corresponding mean value, standard deviation, and distribution law of the error.

2. The experimental method for calibrating the experimental device for photogrammetrically measuring the rock content of soil-rock mixture according to claim 1, characterized in that: In step 2, the transparent model box rotates 3-8 times and then stops.

3. The experimental method for calibrating the experimental device for photogrammetrically measuring the rock content of soil-rock mixture according to claim 1, characterized in that: In step 3, repeat the process of step 2 30-50 times.

4. The experimental method for calibrating the experimental device for photogrammetrically measuring the rock content of soil-rock mixture according to claim 1, characterized in that: In step 4, the specific steps of image processing include: Step 4.1: De-noise the obtained image using a mean filter; Step 4.2: Use the weighted average method to grayscale the denoised image and convert the RGB color image into a grayscale image; Step 4.3: Use a Gaussian filter to denoise the grayscale image and eliminate the noise in the grayscale image; Step 4.4: Use threshold binarization to set the grayscale value of the part with grayscale value greater than the threshold to 255, which is white, and the grayscale value of the part with grayscale value less than the threshold to 0, which is black. Gray and white are used to distinguish between blocks of stone and soil.

5. The experimental method for calibrating the experimental device for photogrammetrically measuring the rock content of soil-rock mixture according to claim 1, characterized in that: In step 5, the specific process of error analysis is to divide the area occupied by the block of stone by the exposed surface area captured in the photo to obtain the calculated stone content corresponding to each photo, the difference between the calculated stone content and the actual stone content of the soil-rock mixture, and the average value, standard deviation and distribution law of the error are obtained through MATLAB.

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