PURPOSE: To repair a soil cement body in an yet unsolidified state by rapidly and easily judging the quality of soil cement by collecting a sample from the soil cement body to calculate the moisture content of the sample and estimating the strength of the soil cement body from a regression equation showing the correlation between the preliminarily calculated moisture content and strength of soil cement in the foundation.

CONSTITUTION: The earth and sand of a predetermined layer is sampled before execution and mixed with cement milk having a predetermined composition to prepare a sample simulating soil cement to be executed. Moisture content and cement quantity are calculated from the sample and the compression strength of the sample is calculated by a compression test to calculate a regression equation showing the correlation between the moisture content, strength cement quantity and strength. A sample is collected from the soil cement immediately after execution and the moisture thereof is evaporated to calculate reduced moisture content. The strength of the soil cement is estimated from the regression equation related to the preliminarily calculated moisture content and strength and the quality thereof is judged within a short time. Therefore, the presence of the depleted part of the soil cement can be rapidly and easily judged and the repairing of the soil cement in an yet unsolidified state is made possible.