An Experimental Study Of The Relationships Between Color, Degree Of Saturation And Matrix Suction Of Unsaturated Soils

Rainfall is one of the major influencing factors of landslides. Owing to seepage resulting from rainfall, the matrix suction in unsaturated soil zone is reduced, which causes the decrease of the shear strength. So, accurate measurement of matrix suction has important engineering and academic significance. However, due to the limitations of experimental techniques, it is time-consuming to measure the matrix suction of unsaturated soil. Rapid measurement of matrix suction becomes one of the primary research problems at this stage in unsaturated soil field.Sand and silt were the main research types of unsaturated soil. This paper researched the relationship between color and matrix suction of unsaturated soil, based on saturation. Matrix suction can be predicted by related indicators on color values of a soil. So, rapid measurement of matrix suction can be realized.Firstly, saturated soil was dried by microwave oven drying method. In this process, colored pictures of soil were taken with camera at different time. Meanwhile, the water content of soil was obtained. Corresponding to the degree of saturation at the same time, the digital information of images of soil was gained by means of digital image recognition capabilities. And the relationship between color and saturation of soil could be gained in the dehumidifying process of soil.Secondly, it was designed production of soil humidifying experiment device in this paper. With this test device, two dry soils were humidified. Compared with dehumidifying test, the relationship between color and saturation of soil was got in the same approach. The relationship between color and matrix suction of unsaturated soil was found in the dehumidifying and moistening test. The results showed that it was similar to the hysteresis phenomenon of adsorption and desorption soil-water characteristic curve.Finally, desorption soil-water characteristic curve, on the basis of the relationship between saturation and matrix suction of sand and silt, was obtained by means of the test measured data through SWCC pressure meter. In comparison with the curve of color and saturation of soil, the relationship between color and matrix suction of soil was obtained. Through the experimental analysis, the conclusion can be drawn that the relationship between color and matrix suction of soil is direct, and some change rules exist between them.