Creep Damage to Structures on Expansive Clay Slopes

A damage survey of residences in subdivisions in San Antonio and Waco, Texas was conducted and a variety of site conditions were recorded. The damage was measured as the width, length, location and orientation of all cracks in the brick veneer exterior of each building. The site conditions included slope; drainage; size, number, type, and distance of each tree from the nearest wall; age; depth of the active zone; and various index properties of the soil. Over one hundred residences were observed in each subdivision and correlations were made by non-linear regression analysis between the observed damage and the site conditions. The slope of the lot was among the more important variables in predicting the expected level of damage. A Kelvin-model of downhill creep damage was hypothesized and non-linear regression analysis upon the measured crack widths, slopes, and sizes of the residences produced creep properties of the soil mass in the field. These field creep properties are compared with the same properties that were measured in a laboratory triaxial creep test.