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Perbandingan pemodelan respon spektra menggunakan analisis discreet point dengan standar perencanaan ketahanan gempa untuk bangunan gedung dan non gedung tahun 2010 (Studi kasus Kecamatan Cilacap Selatan, Kota Cilacap, Provinsi Jawa Tengah) Arifan Jaya Syahbana; Prahara Iqbal
Jurnal Lingkungan dan Bencana Geologi Vol 5, No 2 (2014)
Publisher : Badan Geologi

ABSTRAKPemodelan respon spektra berdasarkan metode Discreet Point dan Standar Perencanaan Ketahanan Gempa Untuk Bangunan Gedung dan Non Gedung Tahun 2010 telah dilakukan dengan mengambil lokasi di Kecamatan Cilacap Selatan, Kota Cilacap, Provinsi Jawa Tengah. Pengeboran teknik dilakukan di dua titik di Kota Cilacap, yaitu BH-02 dan BH-03 untuk mengetahui stratigrafi tanah dan karakteristik fisik tanah daerah penelitian. Studi mengenai respon spektra mutlak dilakukan terutama pada daerah dengan nilai ekonomi dan sosial yang tinggi. Hal ini guna mengantisipasi kegagalan struktur bangunan saat gempa bumi terjadi. Metode yang dilakukan pada studi ini adalah Discreet Point. Metode ini menganggap tanah akan menjadi beban pada suatu sistem pemodelan di tengah lapisan. Input yang dimasukkan adalah Gempa Bumi Chichi, Kobe, dan Kocaeli. Alasannya adalah adanya kesamaan mekanisme dengan gempa bumi yang melanda Kota Cilacap pada tahun 2011. Hasil penelitian memperlihatkan bahwa: input gempa bumi yang mempunyai karakteristik percepatan sama dapat menghasilkan respon spektra yang berbeda apabila durasi efektif gempa bumi berbeda, daerah Cilacap pada titik BH-02 dan BH-03 mengalami deamplifikasi apabila ditinjau menggunakan Standar Perencanaan Ketahanan Gempa Untuk Bangunan Gedung dan Non Gedung (ditulis: SPKGUBG&NG) 2010, sedangkan penelitian ini menghasilkan deamplifikasi untuk lokasi BH-02 dan amplifikasi yang kecil pada lokasi BH-03. Hasilnya, lokasi BH-02 percepatan di batuan dasar dari 0,457g menjadi 0,33g sedangkan lokasi BH-03 dari 0,462g menjadi 0,51g.Kata kunci: Discreet Point, SPKGUBG&NG 2010, respon spektraABSTRACTComparison of response spectra based on modeling method of Discreet Point and Building and Non-Building Earthquake Resistance Planning Standards 2010 has been conducted in South Cilacap District, Cilacap City, Central Java Province. Drilling technique was carried out at two locations in Cilacap City, named BH-02 and BH-03, to know soil stratigraphy, sampling, and physical characteristics of the research areas. Study on response spectra is should be conducted absolutely mainly at the areas of high economic and social values. This study is is carried out to anticipate structural failures when earthquake occurs. The Mmethod applied in this study is Discreet Point. This method assumes that soils will become the load on a modeling system in the middle of the layer. Earthquake inputs applied in the simulation are Chichi, Kobe, and Kocaeli. The reason is that there is similarity in mechanism with the one that hit Cilacap City in 2011. Research results show that: earthquake inputs that have the same acceleration characteristics can result in different response spectra when effective duration of the earthquake is different, the Cilacap area at BH-02 and BH-03 experienced deamplification when viewed using SPKGUBG&NG 2010, while this study resulted in unamplification to the location of BH - 02 and a small amplification at location BH – 03. In this study, the acceleration at BH-02 the bedrock was unumplified from 0, 457g to become 0, 33g, while at location of BH-03 it underwent umplification from 0, 462g to 0, 51g. The result shows that at location of BH – 02 the acceleration in the bedrock which was 0,457g became 0,33g, whereas at location BH – 03 which was of 0,462g became 0,51g.Keywords: Discreet Point, SPKGUBG&NG 2010, response spectra

Pemodelan Hidrologi Longsoran di Lereng Km 1, Jalur Lintas Barat Liwa - Krui, Lampung Barat Prahara Iqbal; Asep Mulyono; Arifan Jaya Syahbana
Jurnal Lingkungan dan Bencana Geologi Vol 7, No 2 (2016)
Publisher : Badan Geologi

ABSTRAKKejadian longsoran di jalur lintas barat Liwa - Krui sering terjadi yang menyebabkan putusnya jalur perekonomian antar- daerah. Longsoran yang terjadi dominan berjenis longsoran translasi tanah yang diakibatkan oleh infiltrasi airhujan. Pemodelan hidrologi di salah satu lereng jalur lintas barat Liwa - Krui Km 1 telah dilakukan dengan tujuan untuk mengetahui proses terjadinya longsoran dan untuk memilih solusi penanggulangan yang tepat. Metode yang digunakan adalah pemetaan geologi, analisis geoteknik, dan pemodelan hidrologi. Pemodelan hidrologi dilakukan dengan simulasi numerik yang menggunakan data laboratorium. Hasil analisis menunjukkan bahwa longsoran yang terjadi di lereng jalur lintas barat Liwa - Krui Km 1 adalah longsoran translasi dangkal yang disebabkan oleh penjenuhan tanah akibat infiltrasi air hujan. Penanggulangan yang dapat dilakukan untuk mengatasi masalah tersebut adalah dengan memasang lapisan impermeabel berupa lapisan semen.Kata kunci: jalur lintas barat Liwa - Krui, longsoran, pemodelan hidrologiABSTRACTLandslide phenomena at Liwa - Krui west cross road oftenly occur causing loss of inter-regional economic lines. The landslide type predominantly is soil translational slide, caused by rain water infiltration. Slope hydrological modeling at Liwa - Krui west cross road Km 1 was conducted with purposed to determine the occurrence of landslide and choose the right mitigation solution. The methodology used consists of geological mapping, geotechnical analysis, and hydrological modeling. Hydrological modeling was carried out by numerical simulation using laboratory data. The analysis show that the landslide on the Liwa - Krui west cross road slopes is translational shallow landslide, triggered by the soil saturation due to rainfall infiltration. The mitigation method that can be applied to overcome this problem is to place an impermeable layer such as cement on the slope face.Keywords: Liwa - Krui West Cross road, landslide, hydrological modeling

Pemodelan 2D perubahan tekanan air pori hubungannya dengan Likuifaksi: Studi kasus Kabupaten Bantul, Daerah Istimewa Yogyakarta Arifan Jaya Syahbana; Khori Sugianti
Jurnal Lingkungan dan Bencana Geologi Vol 4, No 3 (2013)
Publisher : Badan Geologi

ABSTRAKYogyakarta merupakan daerah rawan gempa bumi. Tanggal 27 Mei 2006 terjadi gempa dengan skala 6,2 Mw yang mengakibatkan banyak berjatuhan korban dan kerugian material. Peristiwa ini juga menimbulkan bahaya sekunder yang lain, yaitu likuifaksi. Penelitian ini menyajikan validasi besaran tekanan angka pori yang dapat memicu likuifaksi dengan analisis 2 Dimensi. Pemodelan disimulasikan menggunakan perangkat lunak Liqit untuk mengetahui profil tanah yang berpotensi likuifaksi dan nilai PGAnya. Nilai PGA diaplikasikan pada program PLAXIS untuk mengetahui perkembangan tekanan air porinya. Hasil simulasi menunjukkan perkembangan tekanan air pori di lokasi penelitian ada yang merata dan terlokalisir. Selain itu pendekatan data SPT akan memberikan efek suatu jenis tanah akan lebih mudah mengalami likuifaksi daripada CPTu. Dengan asumsi lebih mudah mengalami likuifaksi maka sebuah profil yang mengalami likuifaksi akan menghasilkan tekanan air pori yang lebih kecil dibandingkan dengan perhitungan CPTu pada nilai PGA yang sama. Simulasi dengan data SPT akan menghasilkan perbandingan tekanan air pori terhadap tegangan total tanah sekisar 61%, sementara pada data CPTu akan memberikan hasil sekitar 88%. Secara teoritis, semakin besar perbandingan, maka kemungkinan likuifaksi akan semakin besar.Kata kunci: likuifaksi, tekanan air pori, 2 dimensiABSTRACTYogyakarta is the area prone to earthquakes. 27th May 2006 earthquake strucked Yogyakarta with a 6.2 Mw scale which resulted in a lot of many casualties and material losses. This incident also raises the danger of liquefaction. This research presents the validation of pore water pressure quantity which can trigger liquefaction with 2 dimensional analysis. Simulated Modeling using the Liqit software to know the profile of the ground which has liquefaction potential and value of the PGA. PGA value then applied to PLAXIS program to determine the pore water pressure developments. The simulation results show the development of pore water pressure in research location are vary, some evenly and localized. In addition, the SPT data approaches will give the effect of a certain soil type will be more prone to liquefaction than CPTu’s one. Assuming more prone to liquefaction, profile will result in smaller pore water pressure than compared with CPTu method on same PGA value. When SPT data used, it will produce the pore water pressure ratio against the soil total stress range on the number 61%, while in the CPTu data will give the results number ranging in 88%. Theoretically, the larger the comparison, the greater the possibility of liquefaction will occur.Keywords: liquefaction, pore water pressure, 2 dimensions

SLOPE STABILITY EVALUATION OF VOLCANIC SOIL AT LIWA-BUKIT KEMUNING WEST TRAFFIC ROAD, WEST LAMPUNG Prahara Iqbal; Asep Mulyono; Arifan Jaya Syahbana
Jurnal Lingkungan dan Bencana Geologi Vol 8, No 2 (2017)
Publisher : Badan Geologi

Slope stability modeling conducted on two cut slopes which has two different volcanic soil types at Liwa-Bukit Kemuning west traffic road, Lampung Barat. Numerical simulations is the method which used. This method describe changes in the value of the safety factor when it rains. Results of the analysis illustrates that the highest safety factor was obtained on the slopes of sandy soil. Modeling illustrates also the decreasing safety factor when it rains.

Desain cut slope chart untuk evaluasi kestabilan lereng di atas badan jalan. Studi Kasus: Cinona, Cisalak dan Cijengkol, Kabupaten Bandung Barat , Jawa Barat Arifan Jaya Syahbana; Adrin Tohari; Eko Soebowo; Dwi Sarah; Khori Sugianti
Jurnal Lingkungan dan Bencana Geologi Vol 4, No 1 (2013)
Publisher : Badan Geologi

ABSTRAKTopografi daerah Jawa Barat didominasi oleh perbukitan yang menyebabkan sering terjadinya peristiwa tanah longsor pada lereng potongan di atas badan jalan, terutama pada musim hujan. Banyaknya frekuensi bencana longsor di atas badan jalan telah menimbulkan kerugian fisik akibat kerusakan jalan dan kerugian ekonomi akibat terputusnya jalur transportasi. Untuk mengurangi kejadian bencana longsor di atas badan jalan, diperlukan pengetahuan tentang desain potongan lereng yang stabil berdasarkan kondisi sifat fisik, hidrologis dan keteknikan tanah setempat yang dapat dicapai dengan penyusunan desain chart lereng potongan (cut slope chart) yang tepat. Tulisan ini bertujuan untuk menghasilkan chart kestabilan lereng kupasan jalan dengan studi kasus di daerah Cinona, Cisalak, dan Cijengkol, Kabupaten Bandung Barat, Jawa Barat. Metode penelitian yang dilakukan adalah investigasi geoteknik terdiri dari uji CPT dan bor tangan pada lereng-lereng tanah residual vulkanik, pengujian laboratorium sifat fisik, hidrologis, kuat geser tanah residual pemodelan numerik infiltrasi air hujan dan kestabilan lereng. Hasil penelitian menunjukkan chart kestabilan lereng kupasan pada badan jalan di lokasi penelitian mempunyai kecenderungan yang sama dimana angka aman menurun seiring dengan bertambahnya kejenuhan tanah lereng dan kemiringan lereng. Kemiringan lereng yang baik adalah tidak melebihi 45°. Hasil studi ini diharapkan dapat berkontribusi terhadap desain lereng kupasan badan jalan yang tepat untuk dapat mengurangi berbagai kerugian ekonomis dan korban jiwa akibat longsor.Kata kunci: badan jalan, cut slope chart, kestabilan lereng, tanah longsorABSTRACTThe topography of West Java is dominated by hills where many slope failures frequently take place on the road cut slopes particularly during the rainy season. The frequent road cut slope failures had caused physical and economical losses due to the disruption of transportation. In order to mitigate the events of slope failures above the roadway, it is important to understand the stable slope cut design based on the in situ physical, hydrological and engineering properties which can be achieved by composing the design cut slope chart. This paper aims to construct a cut slope chart for case study of Cinona, Cisalak, dan Cijengkol, West Bandung Regency, West Java. The methods employed in this study were geotechnical investigation consisted of Cone Penetration Test (CPT) and hand boring carried out in the volcanic residual soil slopes, geotechnical laboratory analysis to obtain the physical, hydrological and shear strength properties of the residual soil and numerical modelling of coupling rain water infiltration and slope stability analyses. The results show that the cut slope charts for the road cut slopes in the study area show similar tendency of decreasing factor of safety along with the increasing slope saturation and inclination. The favorable slope inclination is not exceeding 45°. This study shall contribute to the appropriate design of road cut slope to minimalize economic loss and casualties due to landslides/slope failures.Keywords: road, cut slope chart, slope stability, landslide/slope failure

COMPARISON OF OVERCONSOLIDATED CLAY SETTLEMENTS CALCULATED BY ANALYTICAL 1D TERZAGHI CONSOLIDATION AND BIOT NUMERICAL ANALYSIS Arifan Jaya Syahbana; Dwi Sarah
JURNAL RISET GEOLOGI DAN PERTAMBANGAN Vol 22, No 2 (2012)
Publisher : Indonesian Institute of Sciences

ABSTRACT Consolidation is a phenomenon where air and water in the soil skeleton (i.e clay soil) are forced out due to loading. This condition can occur when clay soil is subjected to loading resulted from pressure in laboratory test, land fill or embankment, building and other structures in the field. Many studies have examined the consolidation of soil through numerical methods and One Dimensional Consolidation Theory of Terzaghi but rarely find a comparison between them. This study aims to find comparison of settlement due to consolidation based on the two methods. A simple simulation using different thicknesses of soil and different loading condition was carried out on saturated and homogenous overconsolidated soil. The settlement calculations were performed by analytical Terzaghi method and numerical analysis. The results obtained for the varied thickness of the soil samples show varied value of relative error which indicates that thickness is one of the factors contributing to the discrepancy of settlement between the methods. Variation of loading condition in each sample showed that the calculation results of two methods would be the quite similar if the loading is in the range of 40-52 kN/m2. Greater loading out of that range would cause the results of analytical analysis to be less than the numerical analysis.

Microzonation of Soil Amplification Based on Microtremor, Spt and Cptu Data in Bandung Basin Anggun Mayang Sari; Eko Soebowo; Afnindar Fakhrurrozi; Arifan Jaya Syahbana; Adrin Tohari
JURNAL RISET GEOLOGI DAN PERTAMBANGAN Vol 29, No 1 (2019)
Publisher : Indonesian Institute of Sciences

Bandung Basin consists of Sunda-Tangkuban Perahu volcanic deposit that is made of lake sediment and an alluvial fan with fine to coarse-grained materials such as clay, silt and sand. The area is surrounded by several earthquake sources such as the Lembang, Cimandiri, and Baribis Faults. Therefore, it is important to understand soil dynamic problems with respect to seismic sources and soil properties. This research aims to investigate velocity amplification of the Bandung Basin using microtremor measurements and site classification based on the Standard Penetration Test (SPT) and Cone Penetrometer Test (CPTu). Velocity amplification was analyzed using the horizonal to vertical H/V spectral ratio, and site classification was determined using and values. Microzonation maps were developed using Geographical Information System (GIS) to determine the correlation between soil velocity amplification and site class. The results revealed that velocity amplification levels in the Bandung Basin vary with a range of 1.3 to 26.5. Site classification ranges from very dense soil and hard rock (class C), stiff soil (class D) to soft clay soil (class E). Site class E dominates the southeast part of the Bandung Basin with a high value of soil amplification. This scientific information is critical for further spatial planning focusing on infrastructure and residential building. Cekungan Bandung berasal dari endapan vulkanik Sunda-Tangkuban Perahu yang terdiri dari sedimen danau dan kipas aluvial dengan material berbutir halus hingga kasar seperti lempung, lanau, dan pasir. Daerah ini juga dikelilingi oleh beberapa sumber gempa yakni sesar Lembang, Cimandiri, dan Baribis. Oleh karena itu masalah dinamika tanah yang dipengaruhi oleh sumber seismik dan sifat tanah perlu menjadi perhatian. Tujuan penelitian ini adalah untuk mengetahui amplifikasi kecepatan tanah di wilayah cekungan Bandung dengan menggunakan alat mikrotremor dan metode site classification berdasarkan uji SPT dan CPTu. Amplifikasi kecepatan dianalisis menggunakan perbandingan rasio spektral H/V dan site classification yang diperoleh dengan menggunakan nilai dan . Peta mikrozonasi disusun menggunakan teknik Sistem Informasi Geografis (SIG) untuk menentukan korelasi amplifikasi tanah dan site class tanah. Hasil penelitian menunjukkan bahwa tingkat amplifikasi kecepatan di Cekungan Bandung bervariasi, berkisar 1,3 hingga 26,5. Site classification berkisar dari tanah yang sangat padat dan batuan keras (kelas C), tanah kaku (kelas D) hingga tanah lempung lunak (kelas E). Hasil penelitian menunjukkan site class E mendominasi bagian selatan Cekungan Bandung dengan nilai amplifikasi tanah yang tinggi. Informasi ilmiah ini diperlukan untuk perencanaan tata ruang kedepannya, dengan fokus pada infrastruktur dan bangunan tempat tinggal.

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