Fragmentation due to Desiccation and Shallow Failures in Clay Slopes: Fid-Bau Portal

Fragmentation due to Desiccation and Shallow Failures in Clay Slopes

Vallejo, Luis E. / Kutschke, Walter G.

High temperatures can be very damaging to clays forming part of natural slopes. High temperatures cause cracking of the clays. The cracking is the result of evaporation and shrinkage. The present study deals with the formation and evolution of cracks in clays as result of high temperatures. At the beginning of the desiccation process of a clay, few cracks form. As time passes, these original cracks interconnect producing the complete fragmentation of the clay. At the end of the fragmentation process, the clay is formed of clay fragments of different sizes. This study uses the fractal dimension concept from fractal theory to measure the particle size distribution of the fragments. The fractal analysis was conducted on bentonite clay samples desiccated in the laboratory and on the giant desiccation polygons found in clays forming part of the Great Basin Playas in the United States. These giant desiccation polygons have three very distinctive shapes: regular random, irregular random, and orthogonal polygon. The level of fragmentation of the clays was measured by the fragmentation fractal dimension. The fragmentation fractal dimension was found to be equal to 2.21 for the regular random polygons, 1.96 for the irregular random polygons, and 3.89 for the orthogonal desiccation polygons. The effect of the level of fragmentation on the stability of shallow failures that the desiccated clay areas could develop is also analyzed in this study.