Abstract
Recently, a methane hydrate-bearing layer located near the islands of Japan has been investigated as a new potential energy resource. This study examined the feasibility of in-situ ground improvement technologies for enhancing carbonate precipitation in the pores of the turbidite layer. First, the authors isolated urease producing bacteria from this methane hydrate-bearing layer in the Japan Sea. Then, two types of laboratory tests (a particle growth test and soil strength improvement test) were conducted using the in-situ microorganisms isolated from the seabed. The main findings of this research are as follows. 1) The urease-producing bacteria inhabit the methane hydrate-bearing layer near the islands of Japan (Pacific Ocean side and Japan Sea side) , 2) The urease-producing bacteria live under high and low salinity conditions, 3) The urea hydrolysis speed is slower than that of other bacteria such as Bacillus pasteurii (1/5 or less), 4) The microbial carbonate precipitation process can increase the particle size compared to that of the original particles coating the calcite layer surface, 5) The mechanism for increasing the soil strength is based on the addition of cohesion as well as a cement treated soil.
