Abstract
Natural soil contains approximately 107 to 109 microorganisms per gram. Considering this large number of microorganisms, it is expected that soil and rock engineering, especially the field of mechanics, may be able to develop a novel eco-friendly technology to improve the sealability of soil and rock. We performed fundamental laboratory tests in order to develop a novel conceptual grout, hereafter denoted as biogrout. Biogrout consists primarily of calcium carbonate, one of the typical cement elements in soil and rock. This compound can fill the voids and cracks in soil and rock using microbial metabolism. We performed separation tests on calcium carbonate in test tubes, examining the effects of several test conditions, including temperature, organic nutrition, and different buffering conditions, on the separation of calcium carbonate when challenged with commercially available dry yeast and microorganisms naturally living in soil. Furthermore, we examined the improvements in the sealability of sand and clay following biogrout improvement, confirming that coefficients of permeability of both soil types decreased by approximately one order of magnitude from those seen for normal soils. Although a number of problems will need to be addressed, these test results indicate that biogrout is a promising candidate to improve ground properties. The development of such a compound has been successful using microbial metabolism.
