Bearing capacity improvement of soft soil subgrade layer with Bio Stabilized Bacillus Subtilis

Abstract

The problem that is often faced in a road construction is a soil subgrade (soft soil). If the subgrade has a low bearing capacity, causing the soil to decrease greatly, so the road construction will quickly be damaged. Method to overcome the problem is bio stabilization with bacteria utilization. The purpose of this research is to know the bearing capacity improvement of soft soil as subgrade layer with bacteria solution of bacillus subtilis. Tests include soil physical and mechanical properties, compaction parameters and CBR tests. This test is based on ASTM for each test. Variations in addition of bacterial solution were 2%, 4%, 6%, 8% and 10% of dry soil weight with 7 days curing time. The results showed that the maximum value of CBR of soft soil was found at 39% on 6% bacterial solution. Increased CBR value from 2.8% to 39% or 13 times than untreated soil. This shows the use of bacterial concentration solution on soft soil significantly increases the bearing capacity.