Measurement of Degree of Saturation on Model Ground by Digital Image Processing

Abstract

The degree of saturation of ground is conventionally measured at discrete points using transducers, soil moisture sensors, etc. In this paper, a novel method was developed to directly measure the degree of saturation of continuous region of ground by noting the variation in color of the ground as the amount of moisture in the soil changes. In this research, a series of experiments was conducted for the purpose of developing a method to measure the degree of saturation of ground by digital image processing. From photo images taken at various soil moisture contents, the colors of the images were converted into numerical values which were then related to known degrees of saturation. The results of the experiments showed that a method to measure the degree of saturation of ground by image processing was possible. The relation between degree of saturation and luminance value can be expressed in terms of second degree function. Good results were obtained for two soil samples with diŠerent colors and grain size distributions. The margin of error was in the order of ±5z. The method was validated through vertical seepage tests, where good agreements were obtained between the measured degrees of saturation by tensiometers and those estimated from the proposed method. The method illustrates the possibility of measuring the degree of saturation of a larger portion of the ground, which is di‹cult to perform using conventional procedures. With this method, contour diagrams of degree of saturation can be produced, making it possible to visualize the propagation of the saturated region.

Face stability of shallow tunnels in partially saturated soil: centrifuge testing and numerical analysis

“…This occurs for degrees of saturation greater than 60%, for which the calibration curves show high variations of saturation for small luminance value variations. Yoshimoto et al (2011) experienced similar difficulties. However, the model is less sensitive to luminance variations corresponding to saturation values below 60% and the decreasing trend of the degree of saturation with increasing distance from the water table is fairly correctly described.…”

“…The degree of saturation of the soil in the model needs to be measured to properly address the unsaturated state. A method has been developed by Yoshimoto et al (2011) to measure the degree of saturation of unsaturated soils by means of digital image correlation (DIC). From photo images taken at various soil moisture contents, the colours of the images are converted into numerical values, which are then related to known degrees of saturation.…”

Laboratory Experiments of Drainage, Imbibition and Infiltration under Artificial Rainfall Characterized by Image Analysis Method and Numerical Simulations

“…Application of the LRM for characterizing flow dynamics in porous media was mainly restricted to qualitative observations, focusing for instance on the location of the water table. Then, Persson (2005) [40] and Yoshimoto et al (2011) [41] directly measured the degree of saturation of an unsaturated porous medium with the LRM by relating variations in the color of the medium to water content changes. A feasibility study with small samples of different soil materials was proposed in the technical note of Persson (2005) [40].…”

“…A feasibility study with small samples of different soil materials was proposed in the technical note of Persson (2005) [40]. Otherwise, Yoshimoto et al (2011) [41] used a bright red food dye and disconnected calibration and experiments to achieve this goal. Belfort et al (2017) [23] combined the advantages of these two approaches to determine water content, and Cremer et al (2017) [42] have proposed an automatic image analysis that detects fingers in infiltration patterns and evaluates their width, velocity, and frequency.…”

“…Therefore, the developed procedure has to account for data conversion, evaluation of the resolution size, selection of a sensitive channel, correction of brightness values for the LRM, and definition of a calibration curve. Concerning color specification, it could be defined either with traditional grey-scale values [34,43], or with red, green and blue (RGB) mean intensities [41]. Gerhard and Kueper (2003) [44] found that the best correlation with fluid saturation was obtained for the saturation component using the hue-saturation-brightness (HSB) system.…”