Perbaikan tanah lempung ekspansif dengan metode biogrouting menggunakan bacillus cereus dan bacillus megaterium = Improvement of ekspansive clay with biogrouting method using bacillus megateri

Zebua, Ester Idha Devin (2021) Perbaikan tanah lempung ekspansif dengan metode biogrouting menggunakan bacillus cereus dan bacillus megaterium = Improvement of ekspansive clay with biogrouting method using bacillus megateri. Bachelor thesis, Universitas Pelita Harapan.

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Abstract

Tanah merupakan material yang krusial di dalam suatu proyek konstruksi. Kekuatan tanah dan deformasi pada tanah sangat berpengaruh besar terhadap konstruksi yang ditopang di atasnya. Namun begitu tidak semua jenis tanah baik untuk digunakan di dalam konstruksi. Salah satu permasalahan terjadi pada tanah lempung ekspansif. Kembang susut pada tanah ekspansif menyebabkan deformasi yang berpotensi merusak struktur di atasnya. Untuk menanggulanginya diperlukan stabilisasi atau upaya perbaikan tanah. Biogrouting merupakan upaya stabilisasi tanah dengan memanfaatkan mikroorganisme berupa bakteri. Pada penelitian ini digunakan bakteri Bacillus megaterium dan Bacillus cereus. Sama seperti makhluk hidup lainnya bakteri memerlukan nutrisi untuk dapat tumbuh dan berkembang. Pada penelitian ini digunakan medium kultur yang terdiri dari yeast extract, dextrose serta limbah cangkang kerang sebagai sumber ion kalsium. Berdasarkan pengujian titrasi diperoleh kadar CaO pada kerang sebanyak 88.32%, sementara CaO yang terlarut di air adalah 38.79%. Bakteri tersebut berperan untuk berikatan dengan ion kalsium sehingga terjadi proses sementasi sehingga terbentuk kalsium karbonat (CaCO3). Melalui proses sementasi ini diharapkan ikatan molekul pada mineral lempung semakin kuat sehingga air tidak mudah masuk. Untuk mengetahui pengaruhnya terhadap derajat ekspansivitas dilakukan pengujian free swell index. Selain itu biogrouting ini diharapkan mampu meningkatkan daya lekat tanah akibat proses sementasi tersebut. Untuk melihat pengaruhnya terhadap daya lekatnya dapat diperoleh melalui pengujian direct shear test dan triaxial unconsolidated unconfined. Berdasarkan pengujian selama hari ke 0, 30, 60 didapat penurunan nilai FSI terbesar mencapai 20%, serta kenaikan parameter kuat geser terbesar pada direct shear mencapai 143.75%, dan triaxial unconsolidated unconfined sebesar 144.58%./Soil is a crucial material in a construction project. Soil strength and deformation in the soil greatly influence the construction that is supported on it. However, not all types of soil are good for use in construction. One of the problems occurs in expansive clay soils. Shrinkage in expansive soil causes deformations that can potentially damage the structure above. To overcome this, soil stabilization or improvement efforts are needed. Biogrouting is an effort to stabilize the soil by utilizing microorganisms in the form of bacteria. In this study, Bacillus megaterium and Bacillus cereus were used. Just like other living things, bacteria need nutrients to grow and develop. In this study, a culture medium consisting of yeast extract, dextrose, and shellfish waste was used as a source of calcium ions. Based on the titration test, the CaO content in shellfish was 88.32%, while the CaO dissolved in water was 38.79%. These bacteria have a role to bind to calcium ions so that the cementation process occurs to form calcium carbonate (CaCO3). Through this cementation process, it is hoped that the molecular bonds in the clay minerals will be stronger so that water does not easily enter. To determine the effect on the degree of expansion, a free swell index test was carried out. In addition, biogrouting is expected to be able to increase soil adhesion due to this cementation process. To see the effect on adhesion, it can be obtained through a direct shear test and triaxial unconsolidated unconfined. Based on the test for days 0, 30, and 60 it was found that the FSI value 20% decreased, as well as an increase in the shear strength parameter in the direct shear by 143.75%, And the triaxial unconsolidated unconfined by 144.58%.

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