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.
Highlights
In roadway planning, the bearing capacity of the subgrade strongly affects the thickness of the pavement, the higher bearing capacity of subgrade soil, thickness of pavement becomes thinner to withstand the traffic load
The results indicate that bacteria bacillus subtilis showed that bacteria that can breed with temperature in Indonesia and produce calcite/ crystal most come from Papua region [5]
The material used in this study is soft soil from Takalar District, Conventional soil sampling using crowbar and shovel, the sample of soil is placed in the sample sack and to get the original water content wrapped with plastic
Summary
The bearing capacity of the subgrade strongly affects the thickness of the pavement, the higher bearing capacity of subgrade soil, thickness of pavement becomes thinner to withstand the traffic load. Bearing capacity of subgrade is influenced by soil type, density, water content, and others. Soil stabilization using bio method with bacillus subtilis bacteria is believed to improve soil characteristics by increasing the bearing capacity of foundation soil, reducing compressibility and permeability, and reducing variation in volume change. The purpose of this research is to know the effect of bacterial addition on soft soil to increase the bearing capacity of the subgrade layer. The advantage of bacillus subtilis bacteria can reduce soil and environment pollution
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