Calcite-induced precipitation methods (CIPMs) have recently become potential techniques in geotechnical engineering for improving the shear strength of sandy soil. One of the most promising methods among them is enzyme-induced calcite precipitation (EICP). In this technique, a mixed solution composed of reagents and the urease enzyme, which produces calcite, is utilized as the grouting material. The precipitated calcite in granular soil provides ties among the grains of soil and limits their mobility, thus promoting an improvement in strength and stiffness and also a reduction in the hydraulic conductivity of sandy soil. This paper discusses the potential increase in the strength and stiffness of the soil, the additional materials for grouting, the effect of these materials on the treatment process, and the engineering properties of the soil. The possible sources of the urease enzyme and the applicability of the EICP method to other soil types are also discussed in this paper. The environmental and economic impacts of the application of EICP are also presented. The envisioned plans for application, potential advantages, and limitations of EICP for soil stabilization are discussed. Finally, the primary challenges and opportunities for development in future research are briefly addressed.

Peningkatan Efisiensi irigasi dapat dilakukan pada saat penyaluran (conveyance), distribusi maupun aplikasi. Kehilangan air dalam bentuk evaporasi, bocoran, rembesan, perkolasi maupun air yang terbuang perlu ditekan sekecil mungkin. Tujuan penelitian ini adalah mengkaji perkolasi lahan sawah yang dilengkapi dengan lapisan kedap buatan dalam kerangka irigasi hemat air dan peningkatan efisiensi. Lapisan kedap dibuat dengan cara memadatkan lapisan tanah di bawah lapisan olah dengan menggunakan soil stamper dan baby roller. Ketebalan lapisan kedap diperoleh sekitar 14 cm dan kekerasan maksimumnya berkisar antara 9.41 kg/cm2 – 13.28 kg/cm2. Besar perkolasi diperoleh berkisar antara 7.9 sampai 21.3 cm/hari. Perkolasi yang relative lebih kecil diperoleh dari lahan yang dipadatkan dengan baby roller. Tetapi perkolasi yang diperoleh ini masih terlalu besar untuk lahan sawah yang hanya sekitar 4 mm/hari. Hal ini mungkin disebabkan oleh kondisi tanah dari lahan tersebut yang mempunyai perkolasi sangat tinggi (508.8 cm/hari).

The applicability of bio-chemical grouting as the environmentally friendly and economically method for liquefaction remediation was evaluated. Several combinations of organic and in-organic precipitations methods were conducted to obtain the optimum grouting solution. Organic precipitation method employs a bio-agent of urease enzyme to dissociate urea into ammonium and carbonate ions. The produced carbonate ions are precipitated as calcite crystals in the presence of calcium ions. Meanwhile, the in-organic methods were performed using chemical compounds only, without the bio-agent. Unconfined compressive strength (UCS) tests were performed to evaluate the applicability of the grouting solutions for improving the soil strength. Grouting solution is injected into the prepared sand samples. The sand samples with a relative density of 50% were treated with one and two PV for 3-day curing times. The experimental results showed that the organic precipitation method produced the high precipitated amount and resulted in the significant improvement in the strength of the treated sand. The presence of the precipitated materials within the grains of soil generated the strength of 272 kPa. The results of this study have elucidated that the organic precipitation method composed of calcium chloride, magnesium sulfate, urea and enzyme of urease may be an alternative soil-improvement technique to prevent the liquefaction susceptibility.

No abstract

Impact of land clearing during construction that generate dustfall and suspended particulate in ambient air is awfully obvious to observe. According to Indonesian standard as stipulated in Government Regulation (PP) no. 41/1999 pertaining to Air Pollution Control, dustfall and suspended particulate are two important parameters of ambient air quality. However, it remains a problem on how to predict the quantity of dustfall and suspended particulate that is potentially generated during construction land clearing due to lack of prediction method. In this research, a simple way to predict this number has been developed by applying mathematical expressions that are based on a series of laboratory and field experiments covering 15 soil types in Java and Sumatra Islands of Indonesia in 2013-2017. The mathematical formulas can now be implemented directly as a part of an environmental impact assessment, especially in the part of impact prediction of land clearing on air quality change. The formula consists of four parameters, i.e. soil types, local wind velocity, soil moisture content, and percentage of land cover. By inputting these four parameters in the mathematical equation simultaneously, one could directly obtain the quantity of dustfall and suspended particulate generation due to any human activity, such as construction land clearing. The quantity of the generated dustfall is expressed in [ton/km2/month], whereas the suspended particulate generation is expressed in [ug/Nm3] in compliance with the national standard of air quality, i.e. PP No.41/1999. Currently, calculation of the generated dustfall and suspended particulate could be carried out faster and even simpler by using a programmed spreadsheet containing all equations, limitations and terms of conditions that have been compiled during the last five year research campaign.