A new soil improvement technique has been proposed in which calcium carbonate is precipitated via microorganism metabolism to reinforce the soil skeleton. The mechanical properties of soil improved by this proposed technique depend on the addition conditions of microorganisms and nutritive salts, the type of soil, and the soil density. It was necessary to develop a mechanical test that could adequately control for the effect of soil improvement; the reliability of the test needed to be high in order to systematically elucidate the effect of soil improvement on the mechanical properties of improved soils. In this paper, a method is proposed for a triaxial test of soils improved by microorganism metabolism. A method for preparing test sample-pieces using a mold was developed. Using this method, the level of calcium carbonate precipitation could be controlled appropriately. Additionally, a specimen for the triaxial test could be trimmed from the middle section of a test sample-piece, throughout which the calcium carbonate was precipitated relatively homogeneously. Furthermore, it was determined that the specimen hardly changed between specimen preparation and performance of the triaxial test. Finally, a series of consolidated drained triaxial compression tests were performed to confirm the applicability of the proposed method.
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