Experimental study on the improvement of liquefaction strength based on the various types of urease production bacterium

Abstract

This paper focused on the enhancement of liquefaction strength at the precipitation rate of calcite to sand mass is approximately 2% by using urease production bacterium. This study examined the feasibility of improving the liquefaction strength by using various enzyme activity speeds with Toyoura sand. Authors used the cyclic triaxial test to evaluate the enhancement of the liquefaction strength with three types of microbes (Bacillus pasteurii isolated from land, Sporosarcina aquimarina isolated from the coast, and an enriched culture from the liquefaction disaster area caused by the 2011 Tohoku earthquake). The main findings were as follows: (1) the enriched culture from the natural foundation area can enhance calcite precipitation within pore spaces in sand based on the urease enzyme; (2) the urea and calcium source concentrations should be adjusted based on the urease activity to take the same weight of calcite by using various kind of bacterium; and (3) a precipitation rate for calcite of 2% - 3% can improve the liquefaction strength based on many kind of urease production bacterium.