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STUDI AWAL: ANALISA KECEPATAN GELOMBANG GESER (Vs) PADA CEKUNGAN TAKENGON DALAM UPAYA MITIGASI GEMPA BUMI Ibnu Rusydy; Khaizal Jamaluddin; Eldina Fatimah; Syafrizal Syafrizal; Fauzi Andika
JURNAL TEKNIK SIPIL Vol 6, No 1 (2016): Volume 6, Nomor 1, September 2016
Publisher : Jurusan Teknik Sipil, Fakultas Teknik, Universitas Syiah Kuala

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Abstract

Abstract: MASW survey to determine the shear wave velocity (Vs) had been conducted in Takengon basin, Aceh Tengah district. The survey aims to identify sediment layers based on Vs analysis and its correlation with the amplification factor. The Vs yielded from MASW survey was based on the dispersion of Rayleigh wave generated by 4 kg sledgehammer and recorded on 24 geophones with 10 Hz. There are 3 locations of MASW measurement in Takengon basin, the first one located on the edge of the basin, the second location was in the middle of the basin, and the last one was located in the southern. The results of Vs from MASW then compared with soil type classification from ASCE 2010 and SNI 1726: 2012. The Vs in the first location dominated by a layer of soft soil (SE) with the Vs less than 175 m/sand indicate as the young sediment in the edge of the basin. The amplification factor is estimated to be 1.2 times of bedrock acceleration. On the second location, Vs ranged between 275-283 m/s and categorized as stiff soil (SD). This category concluded that, in the middle of the Takengon basin, the sediment was consolidated, and the amplification factor would be smaller compared to the first location. On the thirst location, in depth of 6.3 meter and constantly down to 30 meter, there is very dense soil or soft rock (SC) with Vs 372 m/sec in the form of sandstone. The Construction of high-rise buildings is possible around this third location as long as the foundation of the building should reach the depth of very dense soil (SC) at 6.3 meters.Keywords : Shear wave velocity, Vs, Takengon Basin, MASWAbstrak: Survei MASW untuk mengetahui kecepatan gelombang geser (Vs) telah dilakukan di Cekungan Takengon Kabupaten Aceh Tengah. Survei tersebut bertujuan untuk mengetahui kondisi tanah berdasarkan analisa Vs dan hubungannya dengan penguatan gelombang gempa bumi (faktor amplifikasi). Nilai Vs yang didapatkan dari MASW dengan cara memanfaatkan dispersi gelombang permukaan rayleigh dari sumber seismik berupa palu 4 kg dan terekam pada 24 geophone vertikal 10 Hz. Terdapat 3 titik pengamatan Vs di Cekungan Takengon, titik pertama di pinggir cekungan dekat perbukitan, kedua di tengah-tengah cekungan dan ke-tiga di sisi selatan. Hasil pengukuran Vs dari MASW akan dibandingkan dengan pengkelasan jenis tanah dari ASCE 2010 dan SNI 1726:2012. Hasil MASW menunjukkan bahwa nilai Vs di titik pertama didominasi oleh lapisan tanah lunak (SE) dengan nilai Vs kurang dari 175 m/det yang mengindikasi lapisannya masih muda. Di titik pertama ini, efek amplifikasi diperkirakan sebesar 1,2 kali dari nilai percepatan batuan dasar. Di titik kedua, nilai Vs antar 275 – 283 m/det dan masuk dalam kategori tanah sedang (SD). Kategori SD menunjukkan bahwa di tengah-tengah Cekungan Takengon endapannya lebih tua dan terkonsolidasi sehingga efek amplifikasi akan lebih kecil dibandingkan dengan titik pertama. Pada titik ketiga, dari kedalaman 6,3 meter sampai menerus ke bawah ditemukan lapisan tanah keras atau batuan lunak (SC) dengan nilai Vs 372 m/det berupa batupasir. Pembangunan gedung bertingkat tinggi dimungkinkan di sekitar titik ke-tiga ini dengan syarat pondasinya mencapai kedalaman tanah keras (SC) di 6,3 meter.Kata kunci : Kecepatan Gelombang Geser,Vs, Cekungan Takengon, MASW
ANALISIS VS30 LOKASI KECAMATAN SYIAH KUALA DALAM UPAYA MITIGASI BENCANA GEMPA BUMI KOTA BANDA ACEH Khaizal Jamaluddin; Farzian Iqbal; Ibnu Rusydy; Banta Chairullah
JURNAL TEKNIK SIPIL Vol 7, No 2 (2018): Volume 7, Nomor 2, November 2018
Publisher : Jurusan Teknik Sipil, Fakultas Teknik, Universitas Syiah Kuala

Show Abstract | Download Original | Original Source | Check in Google Scholar | Full PDF (505.514 KB) | DOI: 10.24815/jts.v7i2.12351

Abstract

Abstract : Banda Aceh is located at the geological segment vulnerable to earthquake. However as the capital of the Aceh province should be a serious concern in order to minimize the impact of the devastating earthquake. Therefore, the assessment of soil layer amplification using shear wave velocity values is done as one of the disaster mitigation efforts. Shallow seismic testing to get the parameters of shear wave by using MASW method. The results showed that Syiah Kuala subdistrict is divided into two zones of soil layers. The results of analysis Vs30 showed that  Syiah Kuala subdistrict is divided into medium density and soft layers of soil characteristics.Keywords : earthquake, amplification, seismic and shear wave.Abstrak: Kota Banda Aceh terletak pada segmen geologi yang rentan gempa bumi. Bagaimanapun Banda Aceh sebagai pusat kota Provinsi Aceh semestinya menjadi perhatian serius dalam rangka meminimalisir dampak dari bencana gempa bumi. Oleh karena itu, asesmen karateristik amplifikasi lapisan tanah dengan menggunakan nilai kecepatan gelombang geser dilakukan sebagai salah satu bentuk upaya mitigasi bencana. Penelitian dilakukan di Kecamatan Syiah Kuala, Banda Aceh. Pengujian seismik dangkal untuk mendapatkan parameter gelombang geser dengan mengunakan metode MASW. Hasil analisis Vs30 memperlihatkan bahwa Kecamatan Syiah Kuala terbagi menjadi dua karakteristik lapisan tanah yaitu kepadatan sedang dan lunak.Kata kunci : gempa bumi, amplifikasi, seismik dan gelombang geser.
ANALISIS KESTABILAN LERENG BATU DI JALAN RAYA LHOKNGA KM 17,8 KABUPATEN ACEH BESAR Ibnu Rusydy; Nafisah Al-Huda; Khaizal Jamaluddin; Devi Sundary; Gartika Setiya Nugraha
JURNAL RISET GEOLOGI DAN PERTAMBANGAN Vol 27, No 2 (2017)
Publisher : Indonesian Institute of Sciences

Show Abstract | Download Original | Original Source | Check in Google Scholar | Full PDF (926.66 KB) | DOI: 10.14203/risetgeotam2017.v27.452

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Penelitian kestabilan lereng batuan menggunakan metode analisis kinematik lereng dan klasifikasi massa batuan dilakukan di lereng pinggir jalan Banda Aceh – Calang di Km 17,8 di Kecamatan Lhoknga Kabupaten Aceh Besar. Penelitian ini bertujuan untuk mengetahui jenis longsoran yang akan terjadi di masa yang akan datang, menilai kualitas massa batuan pembentuk lereng, dan tingkat kestabilannya berdasarkan klasifikasi SMR. Akuisisi data struktur massa batuan dilakukan di sepanjang lereng menggunakan metode scanline. Data yang diambil berupa arah kemiringan bidang diskontinuitas, arah bidang, dan kondisi bidang diskontinuitas bidang berupa kemenerusan, kekasaran, bukaan, isian, luahan air dan tingkat perlapukan. Analisis kinematik lereng didapatkan berdasarkan hasil proyeksi stereografi dan analisis kualitas serta kestabilan lereng batuan berdasarkan parameter RMR dan SMR. Hasil analisis kinematik lereng menunjukkan jenis longsoran yang akan terjadi di lereng 1 berupa longsoran  baji dan planar. Di lereng 2 dimungkinkan terjadinya longsoran gulingan/toppling karena bidang joint set yang berlawanan dengan arah lereng. Nilai RMR di lereng 1 sebesar 63 dengan kategori batuan Bagus dan RMR lereng 2 sebesar 57 kategori batuan sedang. Nilai SMR terendah di lereng 1 sebesar 29 (kategori Buruk) untuk longsoran planar dan 53 (kategori Sedang) di lereng 2 longsoran gulingan. Lereng 1 memiliki probabilitas kejadian longsor planar sebesar 60%.Rock slope stability was assessed using the slope kinematic analysis method and rock mass classification on the roadside slope of Banda Aceh - Calang at 17.8 Km in Lhoknga Sub-district, Aceh Besar District. This study aims to determine the types of landslides that will occur in the future by determining the Rock Mass Rating (RMR) and analyzing stability based on the Slope Mass Rating (SMR). The data acquisition of rock mass structures performed the scan line method along the slope. The data taken are the dip and the strike of the discontinuity plane, and the conditions of discontinuity in the form of persistence, aperture, roughness, infilling, weathering and Groundwater conditions. Slope kinematic analysis was conducted based on stereographic projection and analyses of both rock slope quality and stability were based on RMR and SMR parameters. The result of the slope kinematic analysis shows that landslides that occur in slope 1 will be in wedge and planar forms. On slope 2, possible failure is in the form of toppling due to the joint set positioned opposite to the slope direction. The RMR value in slope 1 is 63, categorized as Good rock and the RMR in slope 2 is 57, which is in the medium rock category. The lowest SMR value in slope 1 was 29 as a Bad class for planar failure, and 53 as a Normal category in slope 2 is toppling failure. Slope 1 has a 60 % probability of a planar failure event.
ANALISIS MODULUS DEFORMASI MASSA BATUAN PADA SEGMEN JALAN USAID KM 27 HINGGA KM 30 BERDASARKAN KLASIFIKASI MASSA BATUAN Ibnu Rusydy; Nafisah Al-Huda; M Fahmi; Naufal Effendi; Abrar Muslim; Mirna Lubis
JURNAL RISET GEOLOGI DAN PERTAMBANGAN Vol 30, No 1 (2020)
Publisher : Indonesian Institute of Sciences

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.14203/risetgeotam2020.v30.1073

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Penelitian modulus deformasi dan klasifikasi massa batuan mengunakan sistem RMR (rock mass rating) dan GSI (geological strength index) telah dilakukan di Jalan Raya USAID km 27 hingga km 30. Lintasan jalan di daerah ini berada pada batuan yang mengalami deformasi akibat aktivitas tektonik sehingga pada bagian lereng badan jalan ditemukan rekahan-rekahan yang berpotensi longsor, maka diperlukan rekayasa lereng dengan menganalisis dan menilai klasifikasi massa batuan. Penelitian ini bertujuan untuk mengidentifikasi klasifikasi massa batuan dengan RMR (rock mass rating), GSI (geological strength index), dan besaran nilai modulus deformasi massa batuan yang terdapat pada batugamping lempungan. Metode penelitian yaitu dengan melakukan scanline untuk mengambil data orientasi struktur geologi untuk analisis kinematik lereng dan kondisi bidang diskontinuitas (kemenerusan, bukaan, kekasaran, isian, tingkat pelapukan dan kondisi keairan), termasuk kekuatan batuan utuh yang diambil dari lereng batuan untuk menghitung nilai RMR dan GSI. Pendekatan empiris dilakukan untuk mengestimasi nilai modulus deformasi berdasarkan nilai GSI. Hasil penelitian menunjukkan bahwa longsor batuan yang akan terjadi berdasarkan analisis kinematik adalah longsoran jenis planar, gulingan, dan baji. Nilai RMR masing-masing lereng 1, 2, 3 dan 4 adalah sebesar 60, 64, 60, dan 61, sementara nilai GSI sebesar 50, 51, 52 dan 54 secara berurutan. Nilai modulus deformasi massa batuan untuk batugamping lempungan sebesar 50 GPa untuk semua lereng. ABSTRACTS - Rock mass modulus deformation analysis in USAID highways segment km 27th to km 30th based on rock mass classifications. Rock mass modulus deformation and rock mass classifications utilizing RMR (rock mass rating) and GSI (geological strength index) have been conducted in USAID Highways segment from km 27th to km 30th where is built on the rocks which are highly influenced by tectonic force and deformed by tectonic activity; hence, the rock on the slopes are fractured, folded and potentially to failure. These circumstances need a rock engineering approach by applying rock mass classification methods. This research aims to identify the rock mass classifications based on RMR, GSI, and to estimate the rock mass modulus deformation working on rock slope of argillaceous limestone. Scanline approach was utilized in structural geology data acquisition for rock slope kinematic analysis and joints condition (persistence, aperture, roughness, infilling, weathering, and watering) included the strength of intact rock is obtained from rock slope in calculating the RMR and GSI ratings. The empirical approach was deployed in estimating the rock mass modulus deformation based on GSI value. Rock slope kinematic analysis reveals the possibility of rock failure that will be occurred on the slopes are plane, toppling, and wedge failures. The total RMR ratings are 60, 64, 60, and 61 for slope 1, 2, 3, and 4, while the total GSI values are 50, 51, 52, and 54 respectively. Rock mass modulus deformation for argillaceous limestone in this study area is 50 GPa for every slope. 
Delineation of Gold Prospecting Area Based on Total Magnetic Field Anomalies Reduction to The Pole Alvin Caesar Lesmana Ikramsyah; Nazli Ismail; Ibnu Rusydy; Agus Pajrin Jaman
Journal of Aceh Physics Society Volume 7, Number 3, September 2018
Publisher : PSI-Aceh

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Abstract

Telah dilakukan reduksi ke kutub data anomali medan magnetik total untuk mendelineasikan area prospek emas. Intensitas medan magnetik total dikoreksi dengan nilai diurnal dan IGRF untuk mendapatkan anomali medan magnetik total. Reduksi ke kutub anomali medan magnetik total dilakukan untuk menyederhanakan pola kontur anomali di ekuator. Anomali medan magnetik total reduksi ke kutub telah difilter untuk mendapatkan anomali residual yang merefleksikan target benda anomali pada kedalaman yang dangkal. Hasil yang didapat menunjukkan kontur anomali medan magnetik total reduksi ke kutub terlihat lebih sederhana dan mudah untuk diinterpretasi. Aplikasi kedua metode tersebut pada daerah “C” di Jawa Barat telah berhasil diterapkan. Pada low pass filter anomali yang muncul menunjukkan pola smooth yang merupakan efek dari benda anomali regional. Pada anomali residual menunjukkan pola efek dari benda anomali yang dangkal. Nilai anomali medan magnetik total residual yang rendah pada lokasi penelitian diprediksi sebagai tempat terdepositnya emas yang berasosiasi dengan patahan dan zona alterasi yang berada di bagian selatan dan barat lokasi penelitian.Delineation of gold prospecting area based on the total magnetic field anomalies reduction to the pole have been done. The total magnetic field intensity data were corrected by diurnal and IGRF to obtain the total magnetic field anomalies. The total magnetic field values were reduced to the pole to simplify contour shceme in equator and filtered to obtain the residual anomalies which are reflected as shallow depth anomalies. The results showed that the reduction to the pole contour were more simple and easily to be interpreted. Application of both methods in area "C" at West Java Province has been successfully delineating gold deposit in the area. In low pass filter the anomalies showed smooth pattern which are representated as regional effects. The residual anomalies appear as near surface effects. The low magnetic values in the residual data be expected as gold deposit which associated with fault and alteration zones where located in south and west section of the research field. Keywords: magnetic method, the total magnetic field anomalies, reduce to the pole, low pass  filter, gold potential
Studi Kestabilan Lereng Menggunakan Metode Rock Mass Rating (RMR) pada Lereng Bekas Penambangan di Kecamatan Lhoong, Aceh Besar Rijal Askari; Ibnu Rusydy; Febi Mutia
Journal of Geoscience, Mining Engineering, and Technology Vol 1, No 1 (2017): Jurnal Ilmiah Mahasiswa Teknik Kebumian
Publisher : Journal of Geoscience, Mining Engineering, and Technology

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Lereng merupakan bagian yang membentuk sudut kemiringan tertentu terhadap bidang horizontal dari permukaan bumi. Kondisi lereng bekas penambangan yang terdapat di Desa Jantang, Kecamatan Lhoong, Aceh Besar ditemukan adanya bekas longsoran yang diakibatkan kurangnya monitoring yang dilakukan secara berkala. Tujuan penelitian ini untuk mengetahui nilai bobot dari klasifikasi massa batuan Rock Mass Rating (RMR) yang terdapat pada lokasi penelitian. Penelitian ini menggunakan metode Scanline dengan panjang 50 meter dan metode Rock Mass Rating (RMR). Pengumpulan data berupa data struktur kekar yang terdapat pada lokasi penelitian. Hasil Rock Mass Rating (RMR) yang ada pada lokasi penelitian diperoleh nilai bobot total sebesar 73,10. Simpulan dari penelitian ini bahwa nilai klasifikasi massa batuan Rock Mass Rating (RMR) yang terdapat pada lokasi penelitian dapat diklasifikasikan ke dalam kelas II (baik).
Studi Likuifaksi Menggunakan Nilai Poisson’s Ratio di Kecamatan Meurah Dua, Pidie Jaya Sinta Mandasari; Asrillah Asrillah; Ibnu Rusydy
Journal of Geoscience, Mining Engineering, and Technology Vol 1, No 1 (2017): Jurnal Ilmiah Mahasiswa Teknik Kebumian
Publisher : Journal of Geoscience, Mining Engineering, and Technology

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Penentuan potensi likuifaksi berdasarkan Poisson’s ratio telah dilakukan di Kecamatan Meurah Dua Kabupaten Pidie Jaya. Pengukuran dilakukan pada lokasi yang mengalami kerusakan infrastruktur akibat gempa bumi pada tanggal 7 Desember 2016 di Kabupaten Pidie Jaya. Tujuan dari penelitian ini yaitu mengetahui potensi likuifaksi berdasarkan nilai Poisson’s ratio dan jenis lapisan tanahnya. Nilai Poisson’s ratio  dapat dihitung berdasarkan nilai kecepatan gelombang kompresi (Vp) dan nilai kecepatan gelombang geser (Vs). Nilai Vp  dan Vs didapatkan berdasarkan metode seismik refraksi dan MASW (Multhichannel Analysis of Surface Wave). Pengukuran dilakukan sebanyak tiga lintasan dengan menggunakan Seismograf PASI 16S-24P untuk setiap metode. Panjang lintasan untuk metode seismik refraksi 92 meter dan metode MASW 56 meter. Kemudian data Vp diproses dengan menggunakan Software ZondST2D dan data Vs diproses dengan menggunakan Software SeisImager. Nilai Poisson’s ratio yang didapatkan menunjukkan adanya lapisan pasir dan lempung jenuh. Lapisan pasir memiliki porositas yang lebih besar dari pada lapisan lempung jenuh. Porositas yang besar dapat menyebabkan potensi likuifaksi. Sehingga diindikasikan bahwa setiap lintasan pengukuran memiliki potensi likuifaksi. Potensi likuifaksi terbesar di desa Pante Beureune sementara potensi likuifaksi terkecil di desa Meunasah Raya.
Application of Magnetics Method to Mapping the Geothermal Source at Seulawah Agam Area Asrillah Asrillah; Marwan Marwan; Ibnu Rusydy; Gartika Setiya Nugraha
Jurnal Natural Volume 14, Number 2, September 2014
Publisher : Universitas Syiah Kuala

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Abstract

Magnetic method had been employed at Seulawah Agam area in term of unveiling the potentially geothermal source. This method was carried out locally in both the geothermal filed of Heutsz’s Crater and Cempaga’s Crater where the locations are in Seulawah Agam slope which is included in Aceh Besar District. Geologically, the area is mainly controlled by volcanic mudflow and Lam Teuba’s rocks consisting of breccia, pumice and tuff and their age are from Tersier to Resen Period. The deployed equipment consisted of Magnetometer GSM-19T, Proton Sensors, Aluminum Stick, Connection Cable, GPS Antenna, Compass, and Watch. Portable GPS (Global Positioning System), Navigation type (map of the survey area), and complemented by the other technical equipment, such as handy talky, umbrella, pens and notes of observed data. This study was done by following two steps. At first, the base station was established as a reference point for all magnetic data of measurements. Furthermore, recording magnetic data at each point by repeating three times until the last point by following the looping pattern as pathway of measurement both in Heutsz’s crater whose nine point recordings and in Cempaga’s crater whose seventeen points was consecutively done. The data were simply processed by using Microsoft excel that can just plot the magnetic anomaly and interpreted qualitatively being preliminary research. The result showed that at the north pathway had high magnetic anomaly of rocks located at B6 point and it was assumed as the area having the economically mineral in fracture zones. The rocks with low a anomaly value were obtained at –F125 BR is suggested as the thermal sources while at the South pathway from observing station till the Cempaga’s crater was obtained the geological structure as the Sumatran Fault of Aceh’s segment at CK4 point and this finding showed similar correlation with the result of gravity survey at same pathway published in another paper. In conclusion, this method effectively showed that the Seulawah Agam has potency as thermal source.
IDENTIFICATION OF SUBSURFACE STRUCTURE USING SEISMIC REFRACTION METHOD AT JANTHO ACEH BESAR Muhammad Zikrilah; Didik Sugiyanto; Ibnu Rusydy
Jurnal Natural Volume 16, Number 2, September 2016
Publisher : Universitas Syiah Kuala

Show Abstract | Download Original | Original Source | Check in Google Scholar | Full PDF (294.38 KB) | DOI: 10.24815/jn.v16i2.4916

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An identification of subsurface structure in the surrounding area of Aceh Besar regent’s office was conducted by using seismic refraction method. The aims of this study are to determine the velocity value between layers in order to describe thesubsurface layer model, to identify the types of rocks on each layer, and to analyze the depth of bedrock layer located in the subsurface. There are 4 tracks with spaces in between each geophone, and on each track, with the width of 3 m. The total spread on the track is 72 m and the farthest shoot point is 36 m from the farthest geophone point.
KAJIAN STATISTIK SEISMISITAS KAWASAN SUMATERA Warni Asnita; Didik Sugiyanto; Ibnu Rusydy
Jurnal Natural Volume 16, Number 2, September 2016
Publisher : Universitas Syiah Kuala

Show Abstract | Download Original | Original Source | Check in Google Scholar | Full PDF (360.558 KB) | DOI: 10.24815/jn.v16i2.4917

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The research was conducted in order to identify the distribution of seismicity, repeated periods of earthquakes and the probability of earthquake in Sumatra using Likelihood Maximum methods. Earthquake data from the ISC and USGS catalogue were used. Earthquake data from 1914-2014 (100 year span)  with magnitude of (M)≥5 SR and depth (h)≤100 km that is located at 60LS – 100LU and 920BT – 1080BT. The latitude and longitude coordinates were divided into 21 regions. The results showed distribution of seismicity in Sumatran as much as 3634 events of earthquake during the 100 last years. The distribution of seismicity in Sumatra is quite high. From data shown, there was value a, which is between 4.81 - 9.94 and value b which is between 0.54 - 1.32.  This condition indicated an index value of M≥5 SR, which is between 0.006 - 0.076 and repeated periods between 13 - 175 years with the probability of earthquake M≥5 SR between 5.6% - 99.9% for T (time) = 10, 50 and 100 years.