SOIL MECHANICAL CHARACTERISTICS IMPROVEMENT WITH BACTERIAL BIOCEMENTATION TECHNOLOGY

Abstract

The aim of this study is to establish a subgrade layer by field-scale testing using a 6% Bacillus subtilis bacterial solution in Microbially Induced Calcite Precipitation (MICP), altering the bacterial culture's age by four days and curing it for 150 days.  Field-scale testing was carried out, starting with soil property tests, followed by tank tests, bacterial growth, and soil mechanical tests using bacterial solutions. The study found that on the field model scale, the unconfined compressive strength increased with the lengthening of the curing period. However, because of the influence of rainfall, high rainfall lowers the soil's carrying capacity.  In the 14-day to 45-day test, there is a difference in carrying capacity between layer 1 (0–15 cm) and layer 2 (15–30 cm). Comparing Layers 1 and 2, Layer 1 has a higher (qu) value, but Layer 2 has a higher (qu) value during the 60-150 days test. The optimal value of CBR with MICP stabilization is 20% after 150 days of curing. This increased by four times as compared to soil without bacterial stabilization, while the optimum value of compressive strength increased by three times. The SEM analysis reveals that MICP caused calcite to appear on the soil's surface. The results indicated that bacterial bio cementation stabilization is an alternative method of soil improvement that can enhance the mechanical characteristics of the soil, beneficial for the construction of infrastructure, and is environmentally benign.