Ricky Yuda Pratama, Utari Sriwijaya Minaka, Debby Sinta Devi

STUDI EKSPERIMENTAL PENGARUH PERUBAHAN NILAI KADAR AIR TANAH TERHADAP NILAI CBR (CALIFORNIA BEARING RATIO)

Introduction

Studi eksperimental pengaruh perubahan nilai kadar air tanah terhadap nilai cbr (california bearing ratio). Studi eksperimental pengaruh kadar air tanah terhadap nilai CBR (California Bearing Ratio) untuk konstruksi. Temukan bagaimana perubahan kadar air tanah mempengaruhi daya dukung subgrade.

Abstract

Soil water content significantly influences the bearing capacity of a soil. Bearing capacity is the ability of the soil to support construction loads. In a construction project, the subgrade must be able to support the planned loads and meet the requirements for successful construction. This experimental study aimed to determine the soil type, specific gravity, plasticity index, and the effect of changes in soil water content on the CBR values ​​of soaked and unsoaked soil from Lubuk Mumpo Village, Gunung Megang District, Muara Enim Regency. This study involved mixing native soil with mixture percentages of -10% OMC, -20% OMC, and +10% OMC, +20% OMC, to determine the CBR value. Ten soil samples were prepared for this test: 5 unsoaked and 5 soaked samples, based on SNI 1744-2012. The highest CBR values ​​were obtained at 10.94% for the -20% soaking variation (soaked) for 4 days and 5.33% for the -20% unsoaked variation (unsoaked) compared to the original soil. These results indicate that a 20% decrease in water content below the OMC increases the CBR value, while an increase in water content above the OMC decreases the CBR value.

Review

The study, titled "STUDI EKSPERIMENTAL PENGARUH PERUBAHAN NILAI KADAR AIR TANAH TERHADAP NILAI CBR (CALIFORNIA BEARING RATIO)," addresses a fundamental aspect of geotechnical engineering: the critical relationship between soil water content and its bearing capacity, specifically measured by the California Bearing Ratio (CBR). This topic holds significant practical importance for construction projects, as reliable subgrade support is paramount for structural stability and project success. The abstract clearly articulates the study's objective to experimentally determine the influence of varying soil water content on both soaked and unsoaked CBR values, utilizing soil samples from Lubuk Mumpo Village, Indonesia, alongside characterization of soil type, specific gravity, and plasticity index. Methodologically, the research employed an experimental approach, preparing ten soil samples—five for unsoaked and five for soaked conditions—in accordance with SNI 1744-2012. The core of the investigation involved modifying the native soil's water content to specific percentages relative to the Optimum Moisture Content (OMC): -10%, -20%, +10%, and +20%. The findings reveal a compelling inverse relationship between water content and CBR, with the highest CBR values achieved when the water content was decreased by 20% below the OMC. Specifically, the -20% soaking variation yielded a CBR of 10.94% after 4 days, while the unsoaked -20% variation reached 5.33%, demonstrating a significant increase in bearing capacity at reduced moisture levels compared to the original soil. Conversely, an increase in water content above the OMC was found to decrease the CBR value. This study provides valuable preliminary insights into the localized soil behavior at Lubuk Mumpo Village. Its strength lies in its clear experimental design and adherence to established standards, offering a practical demonstration of how moisture management can impact subgrade performance. While the abstract clearly presents the key findings, a more detailed discussion in the full paper on the engineering implications of the observed CBR values (e.g., suitability for different road classifications) and the mechanisms behind the substantial difference between soaked and unsoaked results would enhance its impact. Future research could expand upon these findings by investigating a broader range of soil types, exploring the long-term effects of moisture fluctuation, or examining the economic implications of optimizing soil water content for construction purposes.

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