Shear Strength Characteristics of Stabilized Sedimentary Soil with Bacillus Subtilis Bacteria

Abstract

Sedimentary soils are formed from deposits resulting from weathering of rocks through natural processes. One way to increase the bearing capacity of sedimentary soil is by stabilizing it. The purpose of this study was to determine the effect of variations in the mixture of Bacillus Subtilis bacteria on the characteristics of sedimentary soils and to determine the effect of the curing period on the shear strength of the sediment stabilized by Bacillus subtilis bacteria. Based on the results of physical properties testing, the original soil was classified as ML, which is silt with low plasticity based on the USCS classification system, and classified as soil group A-4, namely silty soil according to the AASHTO classification system. The addition of Bacillus Subtilis bacteria mixed with urea and CaCl2 was proven to increase the value of shear stress, cohesion, and shear angle of the soil. The addition of Bacillus Subtilis with a mixture of urea and CaCl2 to the sedimentary soil accompanied by a curing period was shown to increase the shear stress at the percentage of adding stabilizing agent 8% from 1.25 kg/cm2, 1.45 kg/cm2, and 1.77 kg/cm2 at the beginning to 1.73 kg/cm2, 2.09 kg/cm2, and 2.39 kg/cm2 at 28 days of curing, with an average increase of 35 percent. The cohesion value continued to increase from the initial value of 0.72 kg/cm2 to 1.57 kg/cm2 at 28 days of curing, resulting in an increase in cohesion value of 118 percent. For the value of the shear angle in the soil, there was an increase from the original soil shear angle value of 22° to 31° in a mixture of 8% bacteria with a curing period of 28 days so that there was an increase in the value of the shear angle by 40 percent.