Effect of Tannery Sludge on Soil Shear Strength

The leather tanning industry in Sukaregang, Garut, Indonesia, produces large amounts of waste, primarily wastewater treatment plant sludge, which can pollute the environment. Clay generally has low shear strength, so it requires improvement measures to perform well in construction. This study aims to analyze the effect of adding tannery sludge on the shear strength of clay soil. The study was conducted experimentally in a laboratory using tannery sludge mixtures at 0%, 10%, 20%, and 30% of the soil's dry weight. Testing determined the soil's unconfined compressive strength, which serves as the basis for calculating shear strength. The results show that adding tannery sludge can increase or decrease soil strength. The unconfined compressive strength of untreated soil is 14.57 kN/m², increasing to 18.42 kN/m² at 10% tannery sludge and reaching 20.83 kN/m² at 20% tannery sludge. But at 30% tannery sludge, the unconfined compressive strength decreased to 4.93 kN/m². These results suggest that tannery sludge can serve as a soil stabilization material, with an optimal content of 20%. Using tannery sludge can support more sustainable industrial waste management.