Efek abu sekam padi, limbah kalsium karbit, dan bakteri Bacillus subtilis terhadap stabilisasi tanah = The effects of rice husk ash, calcium carbide residue, and Bacillus subtilis on peat soil stabilization

Sondakh, Juan Eliezer (2021) Efek abu sekam padi, limbah kalsium karbit, dan bakteri Bacillus subtilis terhadap stabilisasi tanah = The effects of rice husk ash, calcium carbide residue, and Bacillus subtilis on peat soil stabilization. Bachelor thesis, Universitas Pelita Harapan.

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Abstract

Tanah gambut merupakan salah satu jenis tanah yang lunak dan memiliki nilai kuat geser yang rendah. Untuk itu, perlu dilakukan upaya stabilisasi tanah sehingga dapat meningkatkan nilai kuat geser tanah. Pada penelitian ini, stabilisasi tanah gambut dilakukan secara dua tahap yaitu menggunakan metode grouting dan biogrouting. Tahap pertama yaitu secara grouting dilakukan untuk menaikkan nilai pH tanah gambut yang rendah dengan menambahkan bahan yang mengandung kalsium dan silika. Hal ini perlu dilakukan karena kondisi pH yang rendah membuat bakteri yang akan ditambahkan pada tahap kedua tidak dapat berkembang dan mempresipitasi CaCO3 dengan optimal. Selain itu, penambahan bahan yang mengandung kalsium dan silika juga akan membentuk proses sementasi sehingga dapat meningkatkan nilai kuat geser tanah. Penelitian ini menggunakan limbah kalsium karbit sebagai sumber kalsium dan abu sekam padi sebagai sumber silika. Tahap kedua yaitu secara biogrouting dilakukan stabilisasi dengan memanfaatkan bakteri Bacillus subtilis untuk mempresipitasi CaCO3 sehingga dapat memperbaiki tanah. Penelitian ini menggunakan medium kultur cair berisi yeast extract, dextrose, dan limbah karbit untuk memenuhi kebutuhan nutrisi bakteri. Tahap kedua dilakukan 30 hari setelah penambahan abu sekam padi dan limbah kalsium karbit pada sampel tanah. Penambahan abu sekam padi dan limbah kalsium karbit menyebabkan nilai pH tanah gambut meningkat hingga lebih dari 7. Selain itu, penambahan kedua bahan ini juga menyebabkan peningkatan nilai kohesi tanah. Pada masa pemeliharaan 30 hari dan 60 hari, nilai kohesi tanah meningkat sebesar 390,19% dan 1.350,98% dibandingkan nilai kohesi tanah gambut tanpa stabilisasi. Penambahan bakteri Bacillus subtilis pada tahap kedua mendapatkan nilai kohesi tertinggi. Pada masa pemeliharaan 60 hari, nilai kohesi tanah dengan bakteri meningkat sebesar 73,78% dibandingkan nilai kohesi tanah grouting tanpa bakteri./Peat soil is a soft soil with a low shear strength. As a result, it is necessary to make efforts to stabilize the soil in order to increase the value of the soil's shear strength. In this study, peat soil stabilization was carried out in two stages, namely using grouting and biogrouting methods. The first stage, grouting, is used to increase the low pH value of peat soil by adding calcium and silica-containing materials. This is necessary because the bacteria added in the second stage are unable to grow and precipitate CaCO3 optimally due to the low pH conditions. Furthermore, the addition of calcium and silica-containing materials will form a cementation process, which can increase the value of the soil's shear strength. In this study, calcium carbide residue is used as a calcium source, and rice husk ash is used as a silica source. The second stage involves the use of Bacillus subtilis bacteria to precipitate CaCO3 in order to increase the value of the soil’s shear strength. This study used a liquid culture medium containing yeast extract, dextrose, carbide residue to meet the nutritional needs of bacteria. The second stage took place 30 days after the rice husk ash and calcium carbide waste were added to the soil sample. The addition of rice husk ash and calcium carbide residue caused the pH value of the peat soil to increase to more than 7. Furthermore, the addition of these two materials increases the cohesion value of the soil. The soil cohesion values increased by 390.19% and 1350.98% after 30 and 60 days of the maintenance period, respectively, when compared to the cohesion values of peat soils without stabilization. The addition of Bacillus subtilis bacteria in the second stage resulted in the highest cohesion value. After a 60-day maintenance period, the cohesion value of the soil with bacteria increased by 73.78% when compared to the cohesion value of the soil without bacteria.

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