Studies on Short Drilled Shaft Failures in Expansive Clayey Soils in a Cold Environment

In the Kaufman County area within the Texas Department of Transportation's Dallas District, several short drilled shaft foundations supporting three-cable median barrier systems were observed to be distressed during severe winter storm conditions in late 2006 to early 2007. A research study was initiated at UT Arlington to determine and understand the mechanisms causing these shaft failures. The ends of the three-cable median barrier systems are fastened to a single drilled shaft foundation. In general, these shafts are short in length and the same dimensions, diameter and length, are typically used for all soil conditions. This paper presents the initial tasks of this study which includes the estimations of loads on the shafts and the design of reaction test piers for the application of inclined loads on the test shafts simulating the field conditions. Lateral load analyses results are utilized in the design of reaction shaft dimensions and spacings between reaction and test shafts. Salient details of analytical approaches used for load calculations are also included.