Shear Strength Behaviour of Sedimentary Soil Stabilized by Fly Ash

Sedimentary soil is made up of deposits that are the consequence of the weathering of rocks that have already been deposited elsewhere by various natural processes, including water, wind, and others. A location with sedimentary soil is the Bili-bili Dam in the South Sulawesi Province's Gowa Regency. Sedimentary soil at this location is quite abundant and has not been used in general, so it can be investigated for its use, namely stability against the influence of external forces on the carrying capacity of the sedimentary soil. Stabilizing the soil is one approach to boost its bearing capacity, particularly for sedimentary soil. The original soil is categorized as group A-4, or silty soil, according to the AASHTO classification system and as ML, or silt with low plasticity, according to the USCS classification system, based on the findings of physical characteristics testing. It has been demonstrated that the soil's cohesiveness and shear angle increase with the addition of fly ash. It has been demonstrated that adding fly ash stabilizing material to the sedimentary soil of the Bili-bili Dam and allowing it to cure increased the cohesion value from the initial soil cohesion value of 0.72 kg/cm2 to 1.70 kg/cm2 after 28 days. With a 20% fly ash mixture and a curing period of 28 days, the shear angle value increased from the initial soil shear angle value of 22 to 31; this is a 40% increase in the shear angle value.