Publications of Research Center for Geotechnology, Indonesian Institute of Sciences
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PENENTUAN LOKASI IMBUHAN AIRTANAH DENGAN PELACAK ISOTOP STABIL 18O DAN 2H DI CEKUNGAN AIRTANAH DATARAN RENDAH SEMARANG, JAWA TENGAH
Get PDFABSTRAK Pengambilan airtanah di dataran rendah Semarang yang tidak terkendali menimbulkan dampak krisis airtanah yang ditandai dengan penurunan muka airtanah dari tahun ke tahun. Ketersediaan airtanah berkaitan erat dengan jumlah imbuhan (recharge) air ke dalam tanah dan jumlah yang diambil. Penentuan daerah imbuhan dilakukan dengan cara melakukan analisis isotop stabil 18O dan 2H dan membandingkannya dengan tipe air serta kondisi hidrologelogi. Untuk keperluan tersebut, telah dilakukan penelitian airtanah di 9 lokasi yang tersebar di wilayah Semarang, yang terdiri atas 7 conto airtanah tertekan dan 2 contoh airtanah tidak tertekan. Hasil yang didapat dari analisis tersebut adalah bahwa airtanah pada akifer yang berumur kuarter berasal dari air yang diresapkan ke dalam tanah di dalam cekungan tersebut, sementara air yang terdapat dalam akifer Formasi Damar berasal dari daerah di ketinggian di atas 400 m dpl yang terletak di selatan Semarang. Di samping itu sesar yang memisahkan sistem akuifer Formasi Damar dengan sistem akuifer kuarter berfungsi sebagai penghalang masuknya airtanah dari bagian selatan ke akuifer kuarter di dataran Semarang
GROUNDWATER CHARACTERISTICS IN JAKARTA AREA, INDONESIA
Get PDFABSTRACT In the Jakarta area (Indonesia), excessive groundwater pumping due to the rapidly increasing population has caused groundwater-related problems such as brackish water contamination in coastal areas and land subsidence. In this study, we adopted multiple hydrogeochemical techniques to understand groundwater characteristic in the Jakarta area. Although almost all groundwater existing in the Jakarta basin is recharged at similar elevations, the water quality and apparent residence time demonstrates a clear difference between the shallow and deep aquifers. Due to the rapid decrease in the groundwater potential in urban areas, we found that the seawater intrusion in shallow aquifer and the shallow and deep groundwaters are mixing, a conclusion confirmed by major ions, Br−:Cl− ratios and chlorofluorocarbon (CFC)-12 analysis
FRACTAL MODEL AND CLASSICAL BLOCK MODEL IN ORE RESERVE ESTIMATION: A COMPARISON
Get PDFABSTRAK Karakteristik yang umum dijumpai pada banyak endapan emas adalah distribusi kadar emas yang eratik dan tidak mengikuti distribusi normal (gaussian) dikarenakan skewness yang tinggi dan pada gilirannya akan membatasi aplikasi beberapa metode estimasi khususnya geostatistik. Salah satu metode yang dapat digunakan untuk menangani populasi data kadar dengan skewness tinggi adalah model fraktal. Di dalam tulisan ini, salah satu model fraktal, number-size model akan diaplikasikan dalam perhitungan cadangan Au-Ag dengan distribusi data kadar yang kompleks dan eratik yang hasilnya akan dibandingkan dengan hasil perhitungan model blok. Dalam tulisan ini, data-data yang diperoleh dari program pemercontohan dengan metode alur di Urat Ciurug, Blok Selatan 3, Level 500 dan 600, Tambang Pongkor dipergunakan sebagai studi kasus. Hasilnya menunjukkan bahwa number-size model dari metode fraktal sejauh ini hanya dapat di- aplikasikan untuk deposit dengan distribusi kadar dan dimensi yang kontinu. Untuk endapan dengan distribusi kadar yang eratik model ini terbatas penggunaannya, dan dalam kasus ini terbatas hanya pada estimasi volum ruah atau tonase bijih dikarenakan perhitungannya di- dasarkan pada distribusi data ketebalan yang cenderung kontinu
ESTIMATION OF S WAVES ATTENUATION IN THE CENTRAL NORTH ISLAND, NEW ZEALAND USING THE NON-PARAMETRIC GENERALIZED INVERSE TECHNIQUE (GIT).
Get PDFABSTRAK Kami menggunakan seismogram dari gempa lokal (Ml = 2–3.8) dengan jarak hiposenter 5–55 km untuk memperkirakan faktor kualitas Q dari gelombang S di Central North Island, Selandia Baru. Metoda bootstrap inversi non-parametric GIT diterapkan untuk mendapatkan fungsi atenuasi pada 20 titik frekuensi yang terletak antara 2 sampai 10 Hz. Besaran Q yang dihitung dari fungsi atenuasi memberikan relasi Qs(f)=6.15±1.22f1.73±0.12. Hasil ini konsisten dengan penelitian tentang atenuasi yang dilakukan untuk daerah gunung api lainnya
EFFECT OF LAND USE ON SPATIAL AND SEASONAL VARIATION OF WATER QUALITY IN CILIWUNG RIVER, WEST JAVA-INDONESIA
Get PDFABSTRACT Study on water quality aspects of Ciliwung river has been conducted from January 2008 to November 2009 to address the impact of land use change on its seasonal variation. Nitrogen compound of NO2 and NH4 were monitored along the Ciliwung river with different time. Land use change within the Ciliwung watershed was analyzed using remote sensing data and correlate with NO2, NO3, NH4 concentration, conductivity and pH along the river. The results showed that in area with higher populated areas such as found in the middle and downstream area of Ciliwung watershed, NO3 concentration is higher. This obvious variation was also observed for conductivity and pH. It was also observed that the more dense area as in the middle and downstream area the change of land use was obvious. The NO3 concentration is much influenced by land use and vegetation change prior to human activity. In general, NO3 observed on October 2008 was higher compared with that observed on January, April and July 2008. In October where it is rainy season, flushing of NO3 is higher and it was transported into the Ciliwung river. The temporal variation is seemed to be due to variation of rainfall generating different runoff and nutrient flushing surrounding river
GROUNDWATER FLOW SYSTEM OF BANDUNG BASIN BASED ON HYDRAULIC HEAD, SUBSURFACE TEMPERATURE, AND STABLE ISOTOPES
Get PDFABSTRACT To recognize the groundwater flow system in the Bandung Basin, two main methods of regional groundwater flow delineation were employed: hydraulic heads and tracers. Two different environmental tracers, i.e. subsurface temperature and stable isotope were applied. The measured temperatures and stable isotope compositions from 19 observation wells lead to the recognition of three types of flow systems within the Bandung Basin i.e., shallow, intermediate and deep groundwater flow system. The recharge area is located in the hills and upland which form the periphery of the plain. The summit area of the southern mountainous complex might have represented the highest recharge area No indication was found for water being recharged at higher elevation in the northern part of the basin which means the recharged water in the Mount Tangkuban Parahu area did not reach the Bandung Plain. This study clearly demonstrates the usefulness of these environmental tracers and hydraulic head measurement in identification of the groundwater flow system of a certain area
SUHU MUKA LAUT DAN PENGARUHNYA TERHADAP PERTUMBUHAN LINIER KORAL KEPULAUAN SERIBU
Get PDFABSTRAK Koral menyimpan informasi perubahan lingkungan. Analisis pertumbuhan tahunan koral telah dipakai sebagai salah satu data untuk mengetahui perubahan lingkungan. Dalam studi ini dilakukan penghitungan pertumbuhan linier koral dari wilayah Kepulauan Seribu. Penghitungan pertumbuhan linier digunakan dengan menganalisis densitometry yaitu luminance dengan software koral XDS. Hasilnya diperoleh data kecepatan pertumbuhan linier dalam urut-urutan waktu yang kemudian dibandingkan dengan data suhu permukaan laut. Hasil dari studi ini menunjukkan koral di wilayah lepas pantai (offshore) pertumbuhan linier tahunannya dipengaruhi oleh suhu lebih besar dibandingkan dengan koral di wilayah laut dekat dataran Jakarta (inshore)
IN SITU MEASUREMENT OF THE SOIL MOISTURE CONTENT PROFILE AT A DECOMPOSED GRANITE CUT-SLOPE
Get PDFABSTRACT Two selected sites at a decomposed granite cut-slope were instrumented with a rain gauge and a series of ThetaProbes installed at depths up to 90 cm from the slope surface. The objective of this study was to evaluate the significance of antecedent soil moisture conditions in controlling the hydrologic responses of the soils at each site. The antecedent moisture content of the soil in Site #1, in general, increases with depth. The response of the soil to saturation process is more or less confined to the shallow depth. On the other hand, the measurement data of the soil in Site #2 showed that the near surface soil exhibits higher antecedent moisture condition than the deeper soil. The ingress of the wetting front could reach more than 90 cm depth during long period of rainfall. Thus, these results suggest that the hydrological response of the soils is spatially variable and is influenced by the antecedent soil moisture conditions within the soil profile. The presence of soil layers, the distribution of macro cracks within the soil profile, and additional lateral source of moisture may also have significant influences on soil response to saturation process
PROYEKSI GEMPABUMI TASIKMALAYA 2 SEPTEMBER 2009 TERHADAP POTENSI BAHAYA KEGEMPAAN DAERAH GARUT DAN SEKITARNYA
Get PDFABSTRAK Kejadian gempabumi tektonik di Kabupaten Tasikmalaya pada tanggal 2 September 2009 berdampak pada rusaknya infrastruktur dan menelan korban jiwa yang tidak sedikit. Dari hasil penelusuran terdapat lima wilayah yang mengalami kerusakan parah akibat guncangan gempabumi tektonik tersebut, yaitu meliputi Kecamatan Pemeungpeuk, Cisompet, Cikelet, Peundeuy dan Banjarwangi. Dari kejadian ini perlu kiranya dibuat peta daerah rawan bahaya sebagai acuan bagi pembangunan infrastruktur pasca gempabumi. Peta daerah bahaya disusun berdasarkan perhitungan percepatan pergerakan tanah maksimum dengan menggunakan informasi kecepatan gelombang seismik S dangkal (Vs30). Peta tersebut kemudian ditumpangtindihkan dengan peta zona longsoran. Hasil pemetaan tersebut kemudian dibandingkan dengan lokasi bencana akibat gempabumi pada tanggal 2 September 2009 yang lalu. Tampak bahwa daerah bencana memang terletak pada wilayah dengan bahaya kegempaan yang tinggi- sedang
PROTOTIP GROUND ENHANCEMENT MATERIAL (GEM) BERBAHAN BAKU Na-BENTONIT KARANGNUNGGAL - TASIKMALAYA SEBAGAI BAHAN SUBSTITUSI GEM IMPOR
Get PDFABSTRACT GEM is one of the composite material which is used as backfill to protect the electronic equipments, communication network and to stem the voltage of the electrical power problem. GEM has been commonly used in Indonesia, but it is still imported. Therefore it is important to look for substitution minerals. The main compositions of GEM are silica (Si), Aluminium (Al) and carbon (C ). Therefore, this research focus on the aluminofilosilicate minerals (bentonite, from Karangnunggal, Tasikmalaya), and charcoal. Laboratory experimentations include characterizations of raw materials, mineral engineering, and developing formulation and prototype of GEM. The result of this characterizations show that Na-bentonite is the most potential material for GEM raw materials (resistivity 514 Ohm cm). Mineral engineering is used to obtain the GEM formula and prototype in powder form with composition of 70% Na-bentonite, 24% charcoal, and 6% NaCl. However, practically it is necessary to add 5% water glass and 36% moisture content into the powder in order to obtain the resistivity of 16.4 Ohm cm. This study results in GEM which is qualified for the grounding materials standard (resistivity < 25 Ohm cm)