Quantification of Cracks and Shrinkage Using Image Analysis

Abstract

Surface cracks and shrinkage in soil affects its geotechnical properties in various ways. Permeability of soil changes due to cracks in clay barriers which lead to development of preferential flow paths for transportation of contaminants. Development of cracks may also lead to decrease in bearing capacity of soil. In case of earth embankments, cracks reduce strength and lead to seepage and percolation problems. Integrity and stability of landfill liners are affected by surface cracks, apart from leachate infiltration. Alignment of embedded pipes can be changed due to the surface shrinkage. They can cause slope instability and can contributes to the land slides in hilly areas. Hence, knowledge of surface cracks and the shrinkage behaviour of soil is essential to improve the understanding and prediction of changes of unsaturated hydraulic properties in heterogeneous and non-rigid soils. This paper is an attempt to introduce a novel methodology for quantifying surface cracks and shrinkage that appears in soil after desiccation under atmospheric conditions using image analysis technique. ImajeJ software has been used for image processing and Matlab for the calculation of surface cracks and shrinkage area. The samples used for the study is synthetic soil obtained by mixing bentonite and fly ash in various proportions. The effect of variable parameters like sample thickness, moisture content, fly ash content and fibres content on the surface cracks and shrinkage of the bentonite-fly ash mix have been studied. From results it was found that CDF and CIF depends on the chosen parameters i.e. fly ash content, moisture content, fibres content and specimen thickness. There was a reduction in CDF and CIF values with increase in fly ash content and fibres content, while it was increased with the increase in moisture content and specimen thickness