An image-based method for quick measurement of the soil shrinkage characteristics curve of soil slurry

Abstract

This paper presents a new method for determining the shrinkage curve. In this method, a 10 mm high, 80 mm diameter cylindrical dish with smooth interior is filled completely with soil slurry and placed on an electronic balance and then subjected to drying. Images of the soil surface are taken periodically from a fixed location, from which the surface area of the shrinking soil mass is determined by converting the images to binary images. The decreasing bulk volume of the soil is determined from the surface area and the varying thickness of the soil, which is determined from the known initial and measured final thickness (measured with calipers) and assuming that the change in specimen thickness is proportional to the change in its radius at any stage of drying. This method compares favorably with results of the balloon method using the same slurry sample material. Data from this method also fits very well to an existing shrinkage curve equation. This method is effortless, less time consuming than existing methods, and data acquisition can be automated. In addition, the shrinkage curve can be obtained in a relatively short period of 48 h as compared to existing methods that take days or even weeks. The limitation of measuring the shrinkage curve on soil slurry as presented in this work is that it does not represent the structural shrinkage zone.