Effect of bacterial calcium carbonate precipitation on compressibility and shear strength of organic soil

In the past few years, the use of bacterial calcium carbonate precipitation has become popular as a ground-improvement technique for sandy soil. However, this technique has not been applied to organic soil. This study focused on bacterial calcium carbonate precipitation and its effect on the compressibility and strength of organic soil. A special injection system was prepared for inducing a bacterial solution into several samples. The bacterial solution was supplied to the samples by gravity for 4 days in specific molds designed for this work. Calcite precipitation was observed by monitoring the changes in the pH value and by measuring the amount of calcium carbonate in the organic soil. The changes in compressibility and strength were measured before and after the bacterial treatment. The test results showed that the pH values in the treatment medium reached the ideal values that are appropriate for calcite precipitation. It was found that the amount of precipitated calcium carbonate in organic soil increased by about 20% in the treated samples compared to that in the untreated samples. Moreover, the test results indicated that the bacterial treatment influenced the compressibility and shear strength of the organic soil. The results were supported by an energy-dispersive x-ray (EDX) analysis.