Foundation method combining clay-cement mixture with geogrid

The soil improvement method based on cement stabilization, which has been widely used as a shallow foundation method, has a shortcoming such as the insufficient reliability for strength and stiffness especially against tensile and bending forces. This shortcoming is mainly due to incomplete mixing of cement powder with cohesive soil and due to cracks caused by the shrinkage of clay-cement mixture. Geogrids have the reliable strength and stiffness for tensile force, while geogrids have little resistance against bending and compressive forces. The combination of geogrid with cement stabilization technique, enables to create a reliable foundation method in which the two kinds of soil improvement methods compensate for the shortcomings each other. In order to practice this idea, the following two schemes are considered. Type-1 spreads a sheet of geogrid at the lower part of clay-cement mixture. Type-2 wraps the whole clay-cement mixture by a sheet of geogrid. This paper reports the results of field model tests of these two schemes.