For the soil around soil-cement columns

mechanical properties will change after column installation. The strength and modulus changes of the surrounding Ariake marine clays during and after deep mixing using two different installation methods

jet grouting method （JGM） and cement-slurry mixing （CSM） method

are presented. Field construction tests are conducted on Ariake marine clay to investigate the mechanical changes. The Ariake clay is a structured clay and sensitive to disturbance. The investigated results from field and laboratory test indicate that the degrees of disturbance （DOD） to the clays around the soil-cement columns depend on the method of mixing. For the aforementioned two installation methods

the average strength ratio of the surrounding sensitive clay is for JGM method of 0.42 and for CSM method of 0.68. Thirty days after mixing

about 44 % original strength is regained for JGM method and for CSM method

it is 40 %. The recovery of the surrounding soil modulus is slower than that of the strength.