The present report concerns the results of experiments on evaluation methods of quality of soil-cement column by deep mixing method. Six improved soil columns in sandy ground and four improved soil columns in loam ground were prepared with different number of remolding respectively. And three kinds of quality evaluation methods were examined for these columns. These evaluation index were variation of resistivity, coefficient of variation of resistivity, coefficient of variation of unconfined compressive strength. We have developed a resistivity method capable of evaluating the quality variations of improved ground immediately after the construction by the axial resistivity changes of cone sensors pressed in the hardening body. At least 100kg/m3 of binder content is necessary to determine resistivity of improved body. The resistivity measuring cones have the Schlumberger type-4 electrode resistivity meter, 25mm in diameter and 200mm in length. Resistivity meter was penetrated into improved column. Applying current at every 50 to 100mm advance, electrical potential was determined. From results of these experiments, we found the existence of correlation between various kinds of evaluation index and blade rotation number. Especially, variation of resistivity and the coefficient of variation of the compressive strength of improved body became small when the blade rotation number increased. Further more, we could show the appreciate blade rotation number for these ground based on these results.
