Toward Estimating Soil Crack Volume.

Accurate estimates of soil crack volume in expansive soils are important for hydrology models to correctly partition precipitation into runoff and infiltration.  As expansive soils lose water, the soil subsides and large surface cracks form.  Vertical soil movement is relatively easy to measure, and scientists have tried to relate changes in the vertical direction with soil crack volume by assuming equi-dimensional shrinkage and using lab-based shrinkage curves.  Another measurement of soil volume change with water loss is the coefficient of linear extensibility (COLE).  For soils with high COLE values, soil subsidence is assumed to occur at a 1 to 3 ratio with water loss.  However, subsidence rates compared to volume loss are observed at less than 1 to 3 on in situ soil pedons.   Additionally, most field research is conducted on high COLE soils without much attention to soils with moderate shrink swell potential.  The goal of this research is to investigate field subsidence with water loss of soils of varying COLE values.  Several soils with varying COLE values will be chosen and vertical soil movement and water content will be measured.  Additionally, soil crack volume will be measured and related to vertical soil shrinkage.