Tanah gambut dikenal sebagai tanah yang sangat lunak dengan kandungan organik tinggi (≥75% ). Tanah gambut memiliki perilaku yang kurang menguntungkan, yaitu daya dukung yang rendah dan pemampatan yang besar. Metode perbaikan tanah, seperti: preloading dengan beban tambahan, kolom pasir, dan galar kayu telah dilakukan untuk meningkatkan perilakunya. Hanya saja, metode tersebut tidak ramah lingkungan karena menggunakan banyak tanah dan kayu. Karena itu, metode stabilisasi menggunakan kapur telah dikembangkan untuk meningkatkan perilaku gambut. Makalah ini menyajikan efektivitas penggunaan abu sekam padi (RHA) dan Fly Ash (FA) sebagai pozolon untuk dicampurkan dengan CaCO 3 sebagai bahan stabilisasi dan pengaruh Usia stabilisasi terhadap perilaku tanah gambut yang distabilisasi. Dalam studi ini, digunakan 10 % Admixture-1 (30% CaCO 3 +70% RHA) dan 10% Admixture-2 (30% CaCO 3 +70 % FA). Pada usia stabilisasi 20-45 hari, perilaku tanah gambut yang distabilisasi meningkat secara signifikan. Pada usia peram diatas 45 hari perilaku gambut yang distabilisasi menurun karena adanya perubahan jelly CaS i O 3 menjadi kristal dan terjadinya dekomposisi serat gambut. Meskipun dua jenis admixture tersebut memberikan hasil yang baik dalam meningkatkan perilaku gambut berserat, tetapi Admixture-2 menunjukkan hasil yang lebih menjanjikan karena ukuran butirannya yang lebih halus dan kemudahannya dalam pelaksanaan pencampuran.
Peat is an organic soil which has very low bearing capacity and very high compressibility; its organic content is higher than 75%. Peat is classified into two categories, amorphous granular peat and fibrous peat (fiber content > 20%). Fibrous peat has higher bearing capacity compared to the amorphous one due to its fiber content. When the fiber undergoes decomposition, however, its bearing capacity drops, and bigger compression takes place. For this reason, decomposition process of fibrous peat has to be accelerated before the construction starts in order to prevent the change of its properties. In this study, lignocellulolytic bacteria was used to accelerate the fiber decomposition. The results show that 10% of bacteria with 28 days of curing period had the optimum results. The fiber content decreased from 50% to 36.67% in 28 days of curing period. The coarse and medium sizes of fiber decreased 5.13% and 22.03%, respectively; but the fine fiber increased 27.16% because of the change of coarse and medium fiber. Its unit weight and specific gravity decreased 6.83% and 7.89%, respectively. The peat compression increased 22.95% compared to the initial one; but the internal friction angle decreased 27.29%.
Compression behavior of stabilized fibrous peat has similar behavior with the initial one. Therefore, one step loading consolidation test is still applicable for the stabilized fibrous peat to predict its compression. The stabilized fibrous peat behavior, however, still depends on the type of the admixture used and stabilization age or curing period. Based on that reason, this study was carried out to study the change of compression behavior of the stabilized peat and to know whether the correction curves developed for laboratory compression parameters are still applicable to predict the settlement of the stabilized peat in the field. For this purpose, two types of stabilizing material adopted, admixtures lime CaCO3+Rice Husk Ash (admix-1) and lime CaCO3+Fly Ash (admix-2). The stabilized peats were cured and tested at different curing periods 20, 30, 45, 60 and 90 days to check their behavior changes. Besides, laboratory models of peat stabilized at different layer thicknesses 1/3H, 2/3H, and H (H=peat sample thickness) were carried out to monitor their settlement under 50kPa load at different curing periods. This settlement is then compared with the predicted settlement. The results show that the fibrous peat stabilized with admixture-2 gives better behavior improvement than the one stabilized with admix-1; it is, however, then slightly decreases after 60 days of curing periods due to the fiber decomposition. Peat stabilized with admix-2 also give first settlement prediction when it is compared to the settlement of stabilized peat in the laboratory model.
The value of soaked-CBR in subgrade soil is very important in the highway pavement thickness design [1]. If the soaked-CBR value of the subgrade does not meet the requirements, it is necessary to improve the soil by blasting with a better material. This is done to prevent damage to the road. Damage to the pavement surface may also cause damage to the subgrade. Alternatively, the damage to the pavement surface begins with damage on the subgrade. If the subgrade decreases in its power - caused by repetitive vehicle loads, otherwise known as repetition vehicle load, then it can collapse the foundation layer, in which - then continues on the surface damage. Based on the phenomenon, this research is conducted to know the change of soaked-CBR value on subgrade soil due to water logging and repetition of vehicle load passing. The result shows that the soaked-CBR value will increase along with the number of vehicles passing up to 25x passings, then down to 50x passings which is the lowest value of all load variations. After 50x passings, CBR value will increase slightly up to 250x passings which then decrease until the end of the research.
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