Studi pengaruh bacillus cereus terhadap konsolidasi tanah lempung ekspansif = Study of the effect bacillus cereus on expansive clay consolidation

Sianto, Felix Samuel (2021) Studi pengaruh bacillus cereus terhadap konsolidasi tanah lempung ekspansif = Study of the effect bacillus cereus on expansive clay consolidation. Bachelor thesis, Universitas Pelita Harapan.

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Abstract

Tanah lempung ekspansif merupakan salah satu jenis tanah yang memiliki sifat kembang susut. Proses perubahan volume tanah yang terjadi dipengaruhi komposisi kadar air. Sifat tersebut dapat mempengaruhi dan menyebabkan deformasi pada konstruksi di atas permukaan tanah. Untuk mencegahnya, dibutuhkan proses stabilisasi. Dalam penelitian ini digunakan sistem stabilisasi biogrouting. Jenis stabilisasi ini merupakan teknologi yang memanfaatkan mikroorganisme untuk proses pengikatan dalam butiran tanah. Mikroorganisme yang digunakan dalam penelitian ini merupakan bakteri bacillus cereus. Untuk memenuhi nutrisi selama perkembangan bakteri maka digunakan medium kultur B4 yang terdiri dari yeast extract, dextrose ion kalsium yang berasal dari limbah cangkang kerang simping. Dengan dilakukannya titrasi diketahui kadar CaO pada cangkang kerang sebesar 80%, dan terjadi peningkatan sebesar 8,5% setelah dilakukan inkubasi selama 18 jam. Bakteri akan berperan dalam pengikatan ion kalsium sehingga membentuk proses sementasi yang mengubah CaO menjadi kalsium karbonat (CaCO3). Karakteristik tanah yang dievaluasi selama penelitian merupakan karakteristik mekanik dengan melakukan pengujian konsolidasi dan permeabilitas. Tanah lempung ekspansif akan dicampurkan bakteri dengan waktu pemeliharaan selama 30 hari. Berdasarkan pengujian tersebut maka didapatkan penurunan konsolidasi sebesar 0,131cm menjadi 0,129 cm pada sampel tanah dengan masa pemeliharaan bakteri 30 hari. Untuk pengujian falling head hari ke-0 nilai kohesi sebesar 1,64376 x 10-6cm/det dan hasil nilai kohesi yang didapatkan pada hari ke 30 sebesar 1,112 x 10-6 cm/det, serta dalam pengujian free swell index menunjukkan penurunan nilai derajat ekspansivitas dari 40% menjadi 10%. / Expansive clay soil is one type of soil that has swelling and shrinkage properties. The changes of soil volume process that occurs will be affected by the composition of the water content. These characteristics can affect and cause deformation in construction above the ground. To prevent this, a stabilization process is needed. In this study, a biogrouting Stabilization System was used. This type of stabilization is a technology that exploits microorganisms for the process bonding of soil particles. The microorganism used in this research was the Bacillus cereus bacteria. To fulfil the nutrients needed during bacterial development, culture medium B4 was used. The medium consisted of yeast extract and calcium ion dextrose derived from scallop shell waste. By doing the titration, the Ca content obtained in the shells was 80%, and an increase of 8,5% occurred after an incubation for 18 hours. Bacteria will play a role in banding calcium ions during the cementation process, which convert CaO to calcium carbonate (CaCO3). Soil characteristics that were evaluated during the study were mechanical characteristics by conducting consolidation and permeability tests. Expansive clay soil will be mixed with the bacteria with a culture time of 30 days. Based on these tests, it was obtained that the consolidation decrease was 0,131 cm to 0,129 cm in the soil sample with a 30-day bacterial culture period. For the Falling Head test on day 0 the cohesion value was 1,64376 x 10-6 cm/sec and the cohesion value obtained on day 30 was 1,112 x 10-6 cm/sec and in free swell index test, it shows decrease in expansiveness grade from 40% to 10%.

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