Judul: Pemanfaatan Material Organik dalam Meningkatkan Kuat Geser Pasir
Abstrak: Penelitian ini dilakukan untuk mengevaluasi pengaruh penambahan kedelai dan susu dalam teknik enzyme mediated calcite precipitation (EMCP) sebagai metode peningkatan kekuatan geser pasir. Pasir terlebih dahulu dievaluasi melalui uji berat jenis dan analisis saringan untuk menentukan klasifikasi pasir. Uji pengendapan kemudian dilakukan untuk menemukan konsentrasi enzim urease, urea, dan kalsium klorida yang optimal dalam larutan EMCP. Larutan tersebut kemudian divariasikan oleh kedelai dan susu dan kemudian digunakan untuk memperbaiki kekuatan pasir melalui metode perkolasi. Pengaruh penambahan kedelai dan susu terhadap kuat geser pasir dianalisis dengan menggunakan uji kuat tekan bebas. Hasil pengujian menunjukan penambahan kedelai 60 g/L meningkatkan kekuatan pasir sepuluh kali lebih tinggi daripada larutan EMCP tanpa bahan tambahan dengan kekuatan maksimum 185 kPa sementara penambahan susu 12 g/L memperoleh kekuatan maksimum kurang dari 12 kPa. Jumlah kalsit yang diendapkan dalam sampel tanah juga dievaluasi melalui uji kuantifikasi kalsit. Kalsit 2.8% dari massa kering tanah terbentuk ketika 60 g/L kedelai ditambahkan. Penelitian ini membuktikan bahwa penambahan kedelai dalam teknik EMCP melalui perkolasi dapat meningkatkan kekuatan geser pasir secara signifikan sedangkan penambahan susu tidak berpengaruh signifikan terhadap kekuatan geser pasir.
Keyword: bahan organik dalam perbaikan tanah, metode perkolasi, teknik presipitasi kalsit, bahan tambahan urease, grouting kimia

Judul: Pemanfaatan Kedelai pada Metode Enzyme-Mediated Calcite Precipitation (EMCP) untuk Perbaikan Parameter Kuat Geser Tanah Pasir
Abstrak: Teknik perbaikan tanah berbasis biocementation yang sedang dikembangkan yaitu perbaikan tanah berbasis presipitasi kalsit. Salah satu metode yang sedang dikembangkan yaitu dengan menggunakan enzim urease murni (EMCP). Akan tetapi, penggunaan enzim urease murni tidak efisien jika digunakan dalam skala besar, sehingga diperlukan alternatif pengganti yaitu menggunakan tepung kedelai. Penelitian ini bertujuan untuk mengevaluasi parameter kuat geser tanah pasir (UCS) dengan injeksi larutan EMCP dengan menggunakan ekstrak kedelai. Penelitian ini menggunakan ekstrak kedelai yang didapat dengan perlakuan saringan dan sentrifugasi. Evaluasi dilakukan dengan menggunakan uji pengendapan kalsit. Larutan perlakuan sentrifugasi memiliki rasio presipitasi yang lebih tinggi dibandingkan perlakuan saringan. Berdasarkan kuantifikasi massa kalsit dan rasio presipitasi, digunakan konsentrasi ekstrak kedelai sebesar 20 g/L sebagai larutan injeksi. Nilai UCS maksimum terbentuk pada umur 28 hari. Nilai UCS pada umur 28 hari pada perlakuan saringan yaitu sebesar 53,63 kPa dan sentrifugasi sebesar 65,55 kPa., Soil improvement technique based on biocementation that is being developed is soil improvement based on calcite precipitation. One method that is being developed is by using pure urease enzyme (EMCP). However, the use of pure urease enzymes is not efficient when used on a large scale, so an alternative is needed, namely using soybean meal. The goal of this study was to evaluate the parameters of the sand soil shear strength (UCS) by injection of EMCP solution using soybean extracts. This study used soybean extracts obtained by filtering and centrifugation treatment. The evaluation was carried out using the calcite precipitation test. Solution with the centrifugation treatment had a higher precipitation ratio than the filtering treatment. Based on the calcite mass quantification and precipitation ratio, a soybean extract concentration of 20 g/L was used in the injection solution. The maximum UCS value was obtained at the 28 days of curing time. UCS values at 28 days of curing time for filtering treatment was 53,63 kPa and centrifugation treatment was 65,55 kPa.
Keyword: Parameter kuat geser, presipitasi kalsit, tanah pasir, tepung kedelai

Judul: Characteristic of Overshooting Top (OT) Based on  Himawari  8  Satellite  as  a  Convective  Cloud  Feature  that  Generates  Extreme Weather in the Java Island Region
Abstrak: Overshooting Top (OT) is a feature at the top of a convective cloud that is associated with extreme weather. Research on OT in tropical Indonesia is still very limited. The existence of geostationary satellites with wide area coverage and fast frequency observations is useful for observing the fast dynamics of the OT life cycle. Therefore, this study intends to analyze the relationship between OT and extreme weather, updraft and thermodynamic conditions of OT when extreme weather occurs, the best objective method for detecting OT in the day time and night time, and the spatiotemporal distribution of OT in the tropical region of Java Island during the 2018-2021 period. Based on visual analysis using visible channel and Himawari 8 sandwich products, 87% of extreme weather events in Java were accompanied by the appearance of OT. It indicates that the presence of the OT pattern is a convection cloud pattern or feature that is closely related to extreme weather events for the Java Island region. The existence of a time lag between the appearance of OT and extreme weather events on Java Island indicates that the OT of convection cloud can be used as a precursor or nowcasting for the appearance of extreme weather. Most of the convective cloud OT features during extreme weather events on Java Island have altitude that were only able to exceed the altitude of the equilibrium level and few were able to exceed the tropopause level of 9 km – 16 km. The difference in atmospheric conditions during extreme weather events on Java Island, which is in the tropics and subtropics, is a strong and unstable convective energy condition characterized by a larger CAPE, as well as unstable KI, LI, SI and TTI values. It is offset by kinematic factors in the form of a weak vertical wind shear (bulk wind shear 0-6 km) and a higher freezing point height. The difference between extreme weather events in the Java Island region and other tropical regions compared to subtropical regions is the strong updraft speed of convection clouds. The IRW Texture COMB algorithm based on the IRW-Texture Gradient modification and the COMB algorithm shows a significant increase in quality for detecting OT and non-OT pixels in Java. Rainy days with rainfall > 50 mm/day are very common in areas with an altitude of > 500 m. On the other hand, the level of convection activity which is indicated by the presence of OT and lightning is significantly reduced in this area. OT of convective clouds appear more frequently during the DJF season and less frequently during the JJA season. OT often appears during the day time and rarely at night time. Most OTs appear in the central part, away from the south and north coasts of Java Island during the day, while OTs that appear near the south and north coasts of Java Island can appear in the morning or afternoon.
Keyword: convective clouds, extreme weather, Overshooting Tops, Himawari 8 Satellite