Abstract A liquefaction hazard assessment for a particular location is important to reduce disasters that may occur in the future. The liquefaction severity assessment for the Anutapura Medical Centre region of Palu-Indonesia was carried out on various pairs between peak ground surface acceleration and earthquake magnitude. It was conducted by first determining the factor of safety for each existing soil layer and applying the formulation prepared by Iwasaki to measure Liquefaction Potential for the entire soil column. The possible severity of liquefaction at these locations was compared based on the limits set by the respective theories of Iwasaki and Papathanassiou. The results showed that the Anutapura Medical Centre location was very susceptible to liquefaction events with a very high potential level of ground surface damage based on the Iwasaki boundary line. The above-mentioned severity by Papathanassiou limits ranges from high to very high.
Soil stabilization using fly ash is an attractive alternative to be developed. Besides reducing industrial waste, it is also economical in terms of costs. With the presence of water, the lime contained in fly ash would be decomposed and undergone a cementation process and a pozolan reaction which would bind the sand grains. In this study, the effect of fly ash content and curing period on the amount of compressive strength and shear strength was observed using an unconfined compressive and direct shear test, respectively. The stress-strain relationships due to shear loads between sand without fly ash and sand with fly ash were compared to see an increase in shear strength due to the addition of fly ash. The results show that the unconfined compressive strength and shear strength of the composite material increase with the addition of fly ash and curing period. But the opposite happened in compressive strain. It was confirmed that the strain to achieve maximum compressive strength decreased with increasing fly ash content and curing period. The fly ash bond was getting brittle with the increasing compressive strength of the composite material made from fly ash and fine sand.
Organic soil has a high content of water and compressibility. Besides that, it has a low specific gravity, density, and shear strength. This study evaluates the applicability of the soybean crude urease for calcite precipitation (SCU-CP) method and its effectiveness in organic soil as a soil-amelioration technique. Various soybean concentrations were mixed with a reagent composed of urea and calcium chloride to produce the treatment solution. Its effect on the hydrolysis rate, pH, and amount of precipitated calcite was evaluated through test-tube experiments. SEM-EDS tests were performed to observe the mineralogy and morphology of the untreated and treated samples. The treatment solution composed of the reagent and various concentrations of soybeans was applied to organic soil. The increasing strength of the organic soil was evaluated using direct shear (DS) and unconfined compression (UCS) tests. The test-tube results show that a hydrolysis rate of 1600 u/g was obtained when using 50 g/L of soybeans with a precipitation ratio of 100%. The mechanical tests show a significant enhancement in the parameters of the organic soil’s shear strength. A shear strength improvement of 50% was achieved in this study. A UCS of 148 kPa and cohesion of 50 kPa was obtained in the treated samples of organic soil. This research elucidates that the SCU-CP is an effective technique for improving organic soil’s shear strength.
Tanah merupakan dasar dari suatu konstruksi bangunan sipil yang menerima dan menahan beban dari suatu struktur diatasnya. Agregat halus merupakan pengisi yang berupa pasir. Ukurannya bervariasi antara ukuran no. 4 dan no. 100 saringan standar Amerika. Abu Terbang (fly ash) merupakan limbah berbahan bakar batu bara yang dikategorikan sebagai limbah berbahaya (Maryoto, 2008). Kuat tekan bebas (qu) adalah harga tegangan aksial maksimum yang dapat ditahan oleh suatu benda uji berbentuk silindris (dalam hal ini sampel tanah) sebelum mengalami keruntuhan geser (ASTM D2166-06). Pengujian ini bertujuan untuk mengetahui nilai kuat tekan bebas pasir halus dan pasir kasar dengan campuran fly ash pada saat kadar air jenuh dengan uji kuat tekan bebas dengan persentase fly ash 20% dengan variasi derajat kejenuhan 50%, 70%, 100% dan lama pemeraman 7, 28, 56 dan 84 hari.
Abstract New gas wells at Tunu field in East Kalimantan are normally perforated using the extreme underbalanced (EUB) technique, in which a large static pressure differential between the wellbore and formation, or initial underbalance, is set before the gun is fired. This requires an operation to unload wellbore liquid, a wireline operation to set an anchoring tool, and several slickline operations to run and retrieve the gun string. The required degree of underbalance depends primarily on rock properties such as permeability, porosity, and strength. A new approach produces a well dynamic underbalance (the transient underbalance just after creating the perforation cavity). By basing the job design on the properties of the reservoir, wellbore, and gun string, the technique consistently minimizes perforation damage and thus maximizes productivity. This technique is based on recent single-shot perforating experiments that show that it is the maximum dynamic underbalance—not the initial underbalance—that governs perforation cleanup. The wellbore pressure was found to vary considerably during the first half-second after the charges were detonated. This variation in wellbore pressure can be manipulated to give a large dynamic underbalance. Perforating with the new technique and electric wireline was performed on 10 wells in the field. Software that considered wellbore geometry, fluid, gun-string selection, and reservoir properties was used to design a specific gun-string configuration and to predict the productivity increase contributed by the underbalance. The jobs were performed smoothly with significant cost savings compared to conventional EUB operations and yielded an increased productivity. Details of the perforating jobs with the new technique will be described, including a cost reduction of approximately 40% and a significant production increase. Testing revealed an average skin value for four wells of −0.29, versus the average skin of 4.73 from 35 conventional EUB perforating jobs executed during the multi-year interval from 2000 to 2004.
Abstract Currently, a soil stabilization approach using fly ash as an effective choice for increasing soil stiffness and strength has emerged. With the presence of water, the lime in the fly ash would be separated, generating cementitious materials binding the grains of sand. In the present study, the influence of curing time and saturation during specimen preparation on the behavior of fly ash-rectified loose-grained sand was observed by performing a series of splitting tensile strength tests. It was found that the splitting tensile strength increases with fly ash content and curing time and decreases with porosity and saturation. The increase in splitting tensile strength due to the reduction in saturation was clarified using microscopic image observations. Fly ash bonds congregate at the contact surface between the grains of sand at a low saturation of 30% and spread evenly on the whole sand surface at a high saturation of 100%. The splitting tensile strength produced at 30% saturation was approximately twofold higher than that at 100% saturation, particularly at one month of curing time. However, the splitting tensile strength at higher saturations approaches that at lower saturations, especially at longer curing times. Porewater evaporation accelerates the self-hardening occurring over time during curing, helping to achieve optimal strength. A reduction in porosity of approximately 0.6% caused by adding fly ash to the mixture can increase the splitting tensile strength by up to twenty-fold in the present study. An equation has been proposed as a function of porosity/volumetric fly ash content, curing time, and saturation during the preparation of the specimen. That equation can be applied convincingly to determine the splitting tensile strength of fly ash-rectified sand.
Penelitian ini dilakukan pada bulan Maret sampai dengan Oktober 2021 dengan tujuan untuk mengetahui luasan kawasan hutan yang telah teralih fungsi di hulu Sungai Sabilambo dan Sungai Balandete dan pengaruhnya terhadap potensi peningkatan debit banjir di kedua sungai tersebut serta alternatif mitigasi yang bisa dilakukan untuk mencegah dampak negatif akibat kegiatan alih fungsi tersebut. Diharapkan dengan adanya penelitian ini dapat memberikan informasi kepada semua pihak yang terkait dengan kegiatan alih fungsi lahan didalam kawasan hutan. Kebutuhan data antara lain data curah hujan, data debit sungai, peta kawasan hutan serta peta tutupan lahan yang dihasilkan dari analisis data SPOT 6/7 perekaman tahun 2013 dan 2017 yang bersumber dari LAPAN dibuat dengan menggunakan metode maximum livelihood classification, dianalisis dengan metode kuantitatif dan kualitatif. Hasil dari analisis tersebut diperoleh bahwa pada tahun 2013 kawasan hutan yang teralih fungsi sebesar 7.34 % dan pada tahun 2017 sebesar 21,66%. terindikasi telah teralih fungsi ini adalah nilai TSS permukaan di Perairan Teluk Kendari tertinggi berada di sekitar aliran Sungai Wanggu berkisar antara 760-781 mg/L, sedangkan terendah berada di mulut teluk yaitu berkisar antara 672-693 mg/L. Kecepatan arus adalah parameter kualitas air yang memiliki pengaruh paling besar terhadap distribusi total suspended solid di Teluk Kendari.
Kata Kunci : alih fungsi, kawasan hutan, sungai, debit banjir
Proper handling of biomass waste can turn waste into something beneficial for society. One way that can be done is to convert biomass waste into quality biochar for energy needs and agriculture as a planting medium. This partnership program is intended to provide education and practical knowledge to the community regarding utilizing biomass waste for biochar production using a double tube reactor. The activities consisted of socialization of the impact of the abandonment of biomass and the benefits of biomass for household energy needs, as well as practical experience of carbonizing biomass by directly involving partner communities. This activity was carried out at Pambulaan Jaya Village Hall attended by 32 community partners and 9 teams from Halu Oleo University. This partnership activity is very relevant for people in the village where most of the population lives as rice and field farmers. The practical knowledge on carbonizing biomass waste was conducted in two days for the two types of biomasses, namely wood chips and coconut shells. The community was very enthusiastic about continuing the carbonization process after they learned about the great benefits of this biochar product for household energy needs, growing media for plantations, and increasing their income.
In recent years, innovative soil improvement methods have provided more environmentally friendly and sustainable solutions for liquefaction countermeasure techniques. One such technology is enzymatically induced calcite precipitation (EICP), in which urease enzyme is used, instead of bacteria, as a promoter for the hydrolysis of urea. Utilizing the urease enzyme itself, which causes Ca2+ and CO32− to precipitate CaCO3 crystals in the void spaces and surface of grains, is more straightforward than using bacteria. In this study, the effects of the degree of saturation during the precipitation of calcite on the behavior of sand that has been lightly cemented using EICP were investigated through a series of undrained cyclic triaxial tests. Liquefaction strength curves correlating the cyclic stress ratio with the number of cycles needed to cause 5% double amplitude (DA) axial strain were compared for treated and untreated sand. It was found that the lower the degree of saturation during calcite precipitation and the higher the calcite content in the samples, the higher the liquefaction resistance of the EICP-treated sand. This can be clearly explained by the spatial distribution of the calcite in the sand. Microscopic observations by scanning electron microscopy (SEM) revealed that, in sand cured at a lower saturation degree, the precipitated calcite tended to be more concentrated at particle contacts than was the case in fully saturated sand. It was confirmed that only 1% of calcite precipitation at a lower degree of saturation (30%) can double the liquefaction resistance. However, excessive strain in the order of 1% degrades the bonding between sand particles.
