Pengaruh tanah stabilisasi bakteri bacillus subtilis dan bacillus amyloliquefaciens terhadap karakteristik tanah lempung berdasarkan uji model fisik di laboratorium

Kusnadi, Yulia (2023) Pengaruh tanah stabilisasi bakteri bacillus subtilis dan bacillus amyloliquefaciens terhadap karakteristik tanah lempung berdasarkan uji model fisik di laboratorium. Bachelor thesis, Universitas Pelita Harapan.

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Abstract

Tanah lempung ekspansif seringkali dikategorikan sebagai tanah yang bermasalah terutama untuk konstruksi lapisan tanah dasar (subgrade) jalan. Sifat- sifat yang kurang mendukung tanah ekspansif sebagai material lapisan tanah dasar antara lain adalah daya dukungnya yang rendah, ekspansivitasnya yang tinggi dan kuat geser tanah yang rendah. Metode MICP (Minerally Induced Calcite Precipitate) merupakan salah satu inovasi perbaikan tanah yang digunakan untuk memperbaiki karakteristik tanah yang bermasalah. Metode ini menggunakan bakteri dan sumber kalsium sebagai penghasil mineral organik CaCO3 yang berfungsi sebagai perekat antar partikel tanah. Pada penelitian ini penggunaan tanah bekas stabilisasi bakteri Bacillus amyloliquefaciens dan Bacillus subtilis diuji pada dua kondisi, yaitu: pada umur 27 bulan tanpa treatment dan penambahan bakteri dan kalsium berupa CaCl2 Pengujian karakteristik tanah seperti potensi kembang susut, kuat geser dan kekuatan daya dukung CBR dilakukan untuk meninjau peningkatan karakteristik tanah lempung yang telah di stabilisasi dengan bakteri. Hasil menunjukkan bahwa tanah bekas stabilisasi Bacillus amyloliquefaciens dan Bacillus subtilis masih menunjukkan peningkatan yang baik setelah berada dalam kondisi untreated. Hal ini dibuktikan dengan adanya peningkatan nilai CBR dan kuat geser sebanyak 2-3 kali dan 4 kalinya T0 (tanah asli). Selain itu, tanah bekas stabilisasi bakteri mampu mengurangi potensi kembang susut tanah lempung. Setelah menambahkan bakteri dengan masa pemeliharaan selama 60 hari pada sampel tanah, tidak terdapat peningkatan nilai kuat geser serta peningkatan pada nilai CBR yang signifikan. Namun, pengujian geser langsung menunjukkan adanya peningkatan nilai kohesi 23,88% dan 21,5% pada sampel BA dan BS berturut-turut.. Ketebalan tanah stabilisasi juga terbukti berpengaruh meningkatkan daya dukung pada batas optimum 20 cm. Penambahan bakteri pada tanah lempung berpengaruh terhadap potensi kembang susut tanah lempung dari potensi pengembangan sangat tinggi ke sedang./ Expansive clay soils are often categorized as problematic soils, especially for road subgrade construction. The properties that do not support expansive soil as a subgrade material include its low bearing capacity, high expansivity and low soil shear strength. The MICP (Minerally Induced Calcite Precipitate) method is one of the soil improvement innovations used to improve the characteristics of problematic soils. This method uses bacteria and calcium sources to produce calcite crystals as an adhesive between soil particles. In this study, stabilized soil by Bacillus amyloliquefaciens and Bacillus subtilis was tested in two conditions, namely: at the age of 27 months without treatment and with the addition of bacteria and calcium in the form of CaCl2. Soil characteristics such as swelling and shrinkage potential, shear strength and CBR carrying capacity were carried out to review the improvement of the characteristics of clay that has been stabilized with bacteria. The results showed that Bacillus amyloliquefaciens and Bacillus subtilis stabilized soils still showed good improvement after being left untreated. This is proved by an increase in the CBR value and shear strength by 2-3 times and 4 times of the original soil. In addition, soil used for bacterial stabilization can reduce the potential for swelling and shrinkage of clay soils. After adding bacteria with a maintenance period of 60 days to the soil samples, there was no significant increase towards the CBR value. However, the result of direct shear test shown an increase to cohesion value by 23,88% and 21,50% for BA and BS samples respectively. The thickness of the stabilizing soil is also proven to have an effect on increasing the bearing capacity at the optimum limit of 20 cm. The addition of bacteria to clay also affects the swelling potential of clay soil from very high to moderate expansion potential.

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