Uniaxial compression experiments were carried out to study on strengths and failures of gypsum samples with three pre-existing contact flaws in non-overlapping geometry. Prepared samples were expected to have same strength by the stress analysis 17) which is based on the simplified linear mechanism. The experimental results demonstrate the effect of the sample's geometries on the compressive strengths, and the failure mechanisms governing the strength characteristics. And then the stress analyses were improved by using the extracted failure mechanisms. The improved analyses show that the predicted compressive strength agrees fairly well with that of experiments.

Uniaxial compression experiments were carried out to study the strengths and failures of gypsum samples with some pre-existing flaws in non-overlapping geometry. These prepared samples were expected to have same strength by the stress analysis 14) which is based on the simplified linear mechanism. The experimental results demonstrate the effect of the sample's geometries on the compressive strengths, and the failure mechanisms governing the strength characteristics. And then the stress analyses were improved by using the extracted failure mechanisms. The improved analyses show that the predicted compressive strength agrees fairly well with that of experiments.