Febriwan Mohamad
Laboratorium Geofisika, Program Studi Teknik Geologi, Universitas Padjadjaran

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PENDUGAAN KETERDAPATAN AKIFER AIRTANAH DENGAN METODE GEOLISTRIK DI KECAMATAN SUKATANI - KABUPATEN PURWAKARTA Febriwan Mohamad; Yusi Firmansyah
Bulletin of Scientific Contribution: GEOLOGY Vol 13, No 3 (2015): Bulletin of Scientific Contribution
Publisher : Fakultas Teknik Geologi Universitas Padjadjaran

Show Abstract | Download Original | Original Source | Check in Google Scholar | Full PDF (604.331 KB) | DOI: 10.24198/bsc geology.v13i3.8411

Abstract

The research area as administratively is located in Sukatani village, District Sukatani, Purwakarta, West Java Province. Based on the relief morphology, strato volcanic facies models and its lithology, geomorphology of Sukatani is strato volcanoes leg with radial drainage pattern. This area height of about 260-300 meters above sea level. Stratigraphy unit of research area is divided into two units, namely Tufic sandstones-Conglomerates, and Alluvium. The study is intended to determine the position and water resources at a certain depth below the surface and determine subsurface conditions. The study based on measurements of geoelectric method of geoelectric 1-D and 2-D configuration of Schlumberger. The results of study are in the form of rock resistivity values. They are interpreted in the cross-sectional shape and correlated with geological and hydrogeological conditions. Based on the resistivity value, distribution layer in the study area are classified into three packages, namely rock low resistivity layer (<35 ohm-meter) expected role as aquiclud layer, a layer of medium resistivity (35-100 ohm-meters) are expected to act as a layer aquifer, and a layer of high resistivity (> 100 ohm-meters) are expected to act as a layer aquifug.
POTENSI AKUIFER KAMPUS ARJASARI BERDASARKAN PENGAMATAN NILAI TAHAN JENIS BATUAN Febriwan Mohamad; Undang Mardiana; Yuyun Yuniardi; Andi Agus Nur; Muhammad Kurniawan Alfadli
Bulletin of Scientific Contribution: GEOLOGY Vol 15, No 2 (2017): Bulletin of Scientific Contribution GEOLOGY
Publisher : Fakultas Teknik Geologi Universitas Padjadjaran

Show Abstract | Download Original | Original Source | Check in Google Scholar | Full PDF (643.285 KB) | DOI: 10.24198/bsc geology.v15i2.13383

Abstract

ABSTRACTGeoelectric measurement was done in order to obtain the presence, depth, thickness, quantity and distribution of aquifers in the study area. Geoelectric was done by applying 1-D Schlumberger configuration (DC sounding). Rock layer with a resistivity value ranges <20 μm indicates rocks with low resistance values, dominates the surface until 50 meters depth with varying thickness. This layer lithology thought to be composed of weathered soil, fine tuff and lapilli tuff. This layer is assumed to act as aquiclude, porous media that can store water but acts as barrier to the flow of groundwater. This lithology group can be filled by water during the rainy season, but in dry season contain very small amount of water. Rock layer with resistivity value ranges between 20 μm - 60 μm interpreted as coarse tuff intercalating with fine tuff, founded at 75 meters depths below the surface. Rock layers with high resistance values (> 60 μm), founded more than 75 meters in the north area, assumed to be volcanic breccia with tuff as matrix, and have small potential to act as aquifer. Keyword: Geoelectric, Schlumberger, Aquifer, Resistivity ABSTRAKPengukuran geolistrik yang dilakukan dalam upaya untuk mendapatkan kehadiran, kedalaman, ketebalan, jumlah dan penyebaran akuifer. Hasil  pengukuran geolistrik (Sounding) dengan konfigurasi Schlumberger Kelompok batuan dengan nilai tahanan jenis berkisar antara  <20 Wm yang mengindikasikan batuan dengan nilai tahanan jenis rendah mendominasi permukaan hingga kedalaman 50 meter dengan ketebalan bervariasi. Lapisan ini diduga memiliki litologi penyusun terdiri atas tanah lapukan, tuf halus dan tuf lapili. Lapisan ini diduga berperan sebagai akiklud, yaitu media berpori yang dapat menyimpan air tetapi tidak dapat mengalirkan airtanah yang dapat terisi oleh air pada musim hujan, namun pada musim kering tidak mengandung air. Lapisan batuan dengan nilai tahanan jenis antara 20 Wm - 60 Wm  diinterpretasi litologi tuf kasar berselingan dengan tuf halus, berada pada kedalaman mulai 75 meter di bawah permukaan. Lapisan batuan dengan nilai tahanan jenis tinggi (>60 Wm), mulai di kedalaman lebih dari 75 meter di bagian utara diperkirakan breksi vulkanik dengan matriks berupa tuf, dan memiliki potensi kecil sebagai akuifer. Kata Kunci: Geolistrik, Schlumberger, Akifer, Resistivitas
KUALITAS BATUAN BEKU ANDESITIS BERDASARKAN PENDEKATAN KUAT TEKAN DAN PETROLOGI Irvan Sophian -; Aton Patonah -; Febriwan Mohamad -
Bulletin of Scientific Contribution: GEOLOGY Vol 9, No 3 (2011): Bulletin of Scientific Contribution
Publisher : Fakultas Teknik Geologi Universitas Padjadjaran

Show Abstract | Download Original | Original Source | Check in Google Scholar | Full PDF (686.214 KB) | DOI: 10.24198/bsc geology.v9i3.8271

Abstract

The quality of infrastructure is related to the materials to be used, especially rock strength. Infrastructure usually uses the rock material as foundation, road materials, etc. Rock samples were taken from Lagadar-Cimahi and Licin-Cimalaka. Petrographic analyses and point load tests were carried out to determine physical and mechanical characteristics. Rock types of Lagadar are andesite and basaltic and Cimalaka are andesite, basalt, and diorite. Rocks of Lagadar are stronger than Licin based on point load test. Point load test of Lagadar rock samples for andesite ranges from 8.17 - 30.57 kg/cm2, basalt ranges from 47.68 -144.03 kg/cm2, and point load test of andesite, basalt, and diorite from Cimalaka ranges between 4.08 - 10.34 kg/cm2, 4.09 -13.83 kg/cm2, and 6.12 kg/cm2 respectively. Rock strength is influenced by mafic mineral content, void ratio, porosity, texture, rock structures, and the degree of weathering.
KARAKTERISTIK ENDAPAN GUNUNG GEDE KAITANNYA DENGAN KETERDAPATAN AIRTANAH UNTUK KEPERLUAN MASYARAKAT DAERAH GEKBRONG KABUPATEN CIANJUR Undang Mardiana -; Febriwan Mohamad -
Bulletin of Scientific Contribution: GEOLOGY Vol 7, No 2 (2009): Bulletin of Scientific Contribution
Publisher : Fakultas Teknik Geologi Universitas Padjadjaran

Show Abstract | Download Original | Original Source | Check in Google Scholar | Full PDF (1005.42 KB) | DOI: 10.24198/bsc geology.v7i2.8238

Abstract

Administratively, Gekbrong area included into Kabupaten Cianjur region; this area is frontier between Kabupaten Cianjur ( Gekbrong) with Kabupaten Sukabumi ( Cimangkok), resides in Cianjur – Sukabumi roadside. Morphologically as centered bevel of Gunung Gede (Volcano mount foot geomorphology set) with inclination bevel of between 5 - 45 % and height between 400 - 1400 meter asl. River drift pattern grows in this area is sub-parallel pattern which mains to Cibeleng river, with relative Northwest – Southeast stream direction. Geology of this area compiled by pyroclastic and laharic rock; consisted of breccia, tuff, lapilli and laharic breccia from Gunung Gede, while laying below it are compilation between Cantayan Formation Breccias component with Upper Miocene age (Mttb), Cantayan Formation Claystone component with Upper Miocene age (Mttc), Resulting Deposit Of Eldest Volcano ( Qot) Early Plistocene age and Mount Gede Lava ( Qyl) Mid Plistocene age, Breccias and lava of Mount Gede ( Qyg) Late Plistocene age (Cianjur Sheet Geological Map; Sudjatmiko, 1972).Geoelectric investigation done on the basis of physical rock properties to electric current, where each different rock will have different resistivity value. This consideration depends on some factors, such as rock age, electrolyte content, rock solidity, number of minerals contained, porosity, permeability and others. Mostly applied geophysical exploration method in subsurface hydrogeology investigation is geoelectric method (resistivity method). This sounding type also called as Vertical Electric Sounding ( VES), aimed to study various rock resistivity to vertical depth below measuring points (measuring point).Geoelectric investigation result show that there are three rock packages based on distribution and contrast of resisivity value which are interval between rugged and fine clastic and shows more laharik process after compared to its geology condition, such as :a.First package is the topmost package which is phyroclastic rock found at interval depth of 0 until - 30 meter with resistivity value of < 50 Ω m , 50 - 100 Ω m and 100 - 150 Ω m. b.Second package, being volcanic rock package found at interval depth of 0 until - 30 meter with resistivity value of < 50 Ω m, 50 - 100 Ω m and 100 - 150 Ω m. c. Third package start t at - 100 meter depth, compiled by rock with resistivity value between 40 - 50 Ω m (lapilian tuff) and 50 - 100Ω m (lapillian matrix supported breccias).
Aquifer Area Investigation Using Resistivity Method in Cikopomayak, West Java, Indonesia Josua Washington Sihotang; Rodrigo Osvaldus; Danny Bona Tua Munte; Nasib Priono; Febriwan Mohamad
Jurnal Geofisika Vol 16 No 3 (2018): Jurnal Geofisika
Publisher : Himpunan Ahli Geofisika Indonesia (HAGI)

Show Abstract | Download Original | Original Source | Check in Google Scholar | Full PDF (6789.911 KB) | DOI: 10.36435/jgf.v16i3.375

Abstract

Administratively, the research area is located in around Cikopomayak Village, Jasinga, Bogor, West Java,Indonesia. Based on the Hydrogeological and Groundwater Basin Map, this research area was classied to non-potential groundwater basin. In addition, when the summer comes, the lack of water will be happened around the area. Consequently, the water reserve wasn't enough to fulll the necessity of freshwater. Thus, the research about identifying aquifer location was needed. This research aims to determine the depth and thickness of aquifer for the alternative ways to overcome the problem, particularly, for the Cikopomayak Village. Theresearch used the geophysical method by modeling the several data such as Geoelectric 1-D to know the aquifer location based on the section of medium resistivity value. Then, the geoelectric data was correlated to the borehole drilling data that is Gamma Ray (GR) Log, Spontaneous Potential (SP) Log, Resistivity Log, and the cutting data. Commonly, the most suitable lithology for an aquifer is sandstone because of its good characteristic of permeability and porosity. Logging data result will show the small value of GR log, SP Log lean-ing to the right, and low-value resistivity for indicating the aquifer zone. Based on geoelectric data, the research zone has 3 groups of resistivity value and lithology that are shaly clay-stone and siltstone with low-value resistivity (0-50 ohm.m), sandy claystone, medium sandstone, and coarse sandstone with medium value resistivity (50-150 ohm.m), fine sand-stone, sandy claystone, and andesite with high-value resistivity (> 150ohm.m). The aquifer system in the research area was classied into 3 groups that are aquifer, aquitard, andaquiqlud.