The Geotechnical Group began the New Year with a lecture on January 11, 2007 that included a pair of presentations by Dr. Allen Sehn and Dr. David Yang, distinguished engineers with experience applying deep soil mixing methods to a variety of geotechnical design challenges. Dr. Sehn kicked off the lecture with a general overview of soil mixing methods, particularly emphasizing the use of single axis mixing. Deep soil mixing involves mechanically incorporating a cementitious binder into soft in-situ soils for the purpose of improving the strength and stability of the soil. The result creates soil-crete columns which are typically three feet in diameter, but which can be as large as seven feet across. These columns are constructed one after another to create configurations within the ground such as walls or grid patterns. The primary factors which most affect the overall performance of mixed soils are the initial soil conditions, the mixing energy applied to the soil by the cutting tool and the content of binder material added during mixing.