*WINNER* Short and Long-Term Chart Solutions for Design of Compacted Clay Slopes

Abstract

This won best undergraduate poster in Civil and Environmental Engineering.

Compacted clay slopes are often constructed for civil engineering projects, such as highway embankments and land development.  Many times, only limited information about soil properties is available at the time of design (e.g. soil classification, Atterberg limits, and relative compaction specifications).  In slope stability analysis, it is important to consider both undrained (short-term) and drained (long-term) conditions when calculating factor of safety. Depending on the soil conditions, one condition will control more than the other.  Recognizing the uncertainty involved with the design inputs, this project determines the factor of safety for both of these conditions with relatively simple numerical models over a range of design conditions. For the undrained conditions, a Matlab program was used to determine the factor of safety, using undrained strength based on a range of compaction conditions.  For drained conditions, a spreadsheet solution was used to solve for the factor of safety considering the effects of long-term softening using a newly developed response surface method.  The calculations for both undrained and drained conditions used variations in geometry and soil properties, including slope angle, slope height, water content, groundwater conditions, and plasticity index to determine the controlling condition. The purpose of this study is to provide design charts that can be used to design compacted clay slopes.  It is anticipated that this project will be especially useful to senior design groups in the TTU CEE department.