The study will help to design microbial mechanisms to improve soil shear strength in the field scale to protect the soil from erosion in mountainous areas and during landslides.
IIT Mandi researchers S. Using a harmful bacterium called pasteurization, it works towards developing sustainable strategies for soil stabilization that hydrolyze urea in calcite secretion. The process does not involve hazardous chemicals and natural resources can be used sustainably.
The research team’s findings were recently published in the journal Geotechnical and Geo-Environmental Engineering of the American Society of Civil Engineers (ASCE). The study was led by Dr. Kala Venkata Uday and co-authored by her MS Scholar, Deepak Mori.
Soil stability is the process of artificially providing long lasting strength to the soil. It is used when construction work must protect the soil from unstable foundations or erosion. Traditionally, mechanical processes such as compression and chemical processes such as the introduction of chemical grout liquids into the soil have been used to stabilize the soil.
Over the past decades, an environmentally friendly and sustainable soil stabilization strategy – microbial induced calcite receptivity (MICP) – has been investigated worldwide. In this method, bacteria are used to make calcium carbonate (calcite) in the soil pores, which cement the individual grains together, thereby increasing the strength of the soil.
Researchers Has used a harmless bacterium called pasteurization which hydrolyzes urea to induce calcite. The use of urea is particularly attractive because it does not contain hazardous chemicals and natural resources can be used sustainably. Their experimental setup consisted of a sand column containing a mixture of bacteria and cementing solution containing urea, calcium chloride, nutrient broth, etc.
Since a number of parameters were involved, the researchers used the Taguchi method to analyze the effects of these different parameters on soil strength increase by MICP. The use of orthogonal arrays in this method involves organizing the parameters that affect any process and at what level they should be varied. The Taguchi method enables the analysis of many influential parameters without the corresponding requirement for many tests.
Researchers have found that the amount of calcite is not as important as the size and location of the calcite granules formed in the pores during the process.
Higher cementing solution concentration results in higher strength improvement. Similarly, the flow rate and supply rate of the cementing solution also affect the strength increase. There was an optimal value for these parameters that maximized calcite accumulation and consequently increased optimal energy.