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Distribusi Vektor Aliran Air Tanah Dua Dimensi dalam Media Rekahan di Big Gossan, Tembagapura, Papua Hutasoit, Lambok M.; Daryono, Mudrik R.; Widodo, Lilik Eko; Syaifullah, Toddy
Jurnal Teknik Sipil Vol 17, No 2 (2010)
Publisher : Institut Teknologi Bandung

Show Abstract | Download Original | Original Source | Check in Google Scholar | Full PDF (2857.046 KB)

Abstrak. PT. Freeport Indonesia (PTFI) berencana membuka tambang bawah tanah baru di Big Gossan dengan metode stope mine, yang menuntut daerah yang akan ditambang berada dalam kondisi kering. Di beberapa lokasi uji, air tanah keluar dari beberapa lubang stope dengan debit yang cukup mengganggu, tetapi di beberapa lokasi lainnya lubang berada dalam kondisi kering. Pemodelan hidrogeologi terdahulu, yang mengasumsikan bahwa akifer adalah media antar butir, tidak dapat menjawab variasi keberadaan air tanah tersebut. Akifer di daerah ini disusun oleh rekahan-rekahan. Dalam penelitian ini, dilakukan kembali pemodelan hidrogeologi dengan penekanan bahwa akifer adalah media rekahan dan pada titik-titik perpotongan antara sesar dan sungai terjadi peresapan. Dalam pemodelan ini, pertama-tama dilakukan analisis geometri dan orientasi rekahan. Hasil analisis digunakan untuk menghitung distribusi muka air tanah dengan Metode Gale dan konduktivitas hidrolik akifer dengan Metode Oda dkk. Kedua parameter tersebut digunakan untuk melakukan pemodelan hidrogeologi dalam dua dimensi, untuk mengetahui distribusi vektor aliran air tanah. Dari penelitian ini diperoleh bahwa konduktivitas hidrolik di daerah ini adalah heterogen, bukan homogen, seperti asumsi dalam pemodelan terdahulu. Hasil pemodelan hidrogeologi menunjukkan bahwa aliran air tanah terkonsentrasi disebelah barat laut dari Stope # 6.Abstract. PT. Freeport Indonesia (PTFI) is planning to open a new underground mine at Big Gossan by using stop mine method which requires dry mining area. In some pilot areas, groundwater flowed from some stope holes significantly, while in other areas, some holes were dry. Previous hydrogeologic modeling, assuming that aquifers were intergranular media, cannot answer the variation of the groundwater occurrence. The aquifers in the study area are composed of fractures. In this research, hydrogeology of the area is remodeled, stressing that the aquifers are fractured media and recharge takes place at the intersections of faults and rivers. In this modeling, fracture geometry and orientation are analysed first. The results are used to calculate groundwater table distribution by using Gale Method and hydraulic conductivity by using Oda et.al. Method. Both parameters are used to construct two dimensional hydrogeological modeling, to know distribution of groundwater flow vector in the research area. This research reveals that hydraulic conductivity in this area is heterogeneus, not homogeneous, as was assumed in the previous modeling. The hydrogeologic model shows that groundwater flow is concentrated to the northwest of Stope # 6.

Fuzzy-Based Prediction of Spatio-Temporal Distribution of Wet Muck in Block Cave Mine of PT Freeport Indonesia Widodo, Lilik Eko; Widijanto, Eman; Faadhilah, Iftikhor; Sunyoto, Wahyu
Journal of Engineering and Technological Sciences Vol 50, No 2 (2018)
Publisher : ITB Journal Publisher, LPPM ITB

Mud rushes, or wet muck spills, are hydro-geotechnical challenges in block cave mines where wet muck spills out of drawpoints formed by the accumulation of fine materials and water in drawbells. The purpose of this paper is to share the results of the developement of an improved predictive tool that can be used to manage wet muck spills. The tool was developed based on the hybrid modeling of wet muck distribution using fuzzy logic and fuzzy number operations. The fuzzy logic operations were applied to model the spatial distribution of wet muck classes, providing the spatial model of drawpoint status based on five contributing factors, i.e. the height of draw, the water content, the grain size of the fine material, rainfall, and no-mucking days. The fuzzy number operations were used in accordance with the mass balance principle to estimate the temporal distribution of wet muck that forms a mud deposit consisting of fine materials and water in a drawbell. The mass balance principle was expressed using the fuzzy ordinary differential equation, including the uncertainty of joining variables. A wet muck spill event at the Deep Ore Zone (DOZ) block cave mine of PT Freeport Indonesia was utilized as a case study as well as to validate the proposed method. The fuzzy-based approach shows promising results in predicting wet muck spill events.

Physical Model of Vertical Water Movement Inside a Soil-Column Apparatus for Infiltration Study with A Two-Way Orientation Approach Fajar, Reza Adhi; Handayani, Gunawan; Notosiswoyo, Sudarto; Widodo, Lilik Eko; Pamungkas, Tri Chandra
Journal of Engineering and Technological Sciences Vol 51, No 5 (2019)
Publisher : ITB Journal Publisher, LPPM ITB

To improve the theory of Richard?s equation, studying infiltration under free-draining conditions at the ground surface is necessary. Verification is required to clarify the physical model of water movement. The aim of this study was to describe multistage measurements of both the wetting and the drying front scheme of one-dimensional infiltration at laboratory scale. A soil-column infiltration apparatus was built consisting of a double acrylic wall, a sensor set and a light bulb. Acrylic was chosen as the material for the wall to minimize possible heat conduction on the wall side, which was wrapped in double insulation to achieve adiabatic condition. The following three main sensors were used and controlled by a microcontroller: water-content, pressure and temperature sensors. Meanwhile, the light bulb at the top of the apparatus was set to non-isothermal condition. The instrument was successfully built to describe vertical water movement. Slight modifications were carried out to ensure more precise observation. This resulted in the initiating of new shape interpretation based on the water-ponding measurement to refine the simplified pattern that was introduced by the conventional Green-Ampt theory.

Hydraulic Conductivity Modeling of Fractured Rock at Grasberg Surface Mine, Papua-Indonesia Tedy Agung Cahyadi; Lilik Eko Widodo; Zuher Syihab; Sudarto Notosiswoyo; Eman Widijanto
Journal of Engineering and Technological Sciences Vol. 49 No. 1 (2017)
Publisher : Institute for Research and Community Services, Institut Teknologi Bandung

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.5614/j.eng.technol.sci.2017.49.1.3

Packer tests and slug tests were conducted at 49 points at the Grasberg surface mine, Indonesia to obtain hydraulic conductivity data. The HC-system approach, which relies on rock quality designation, lithology permeability index, depth index, and gouge content designation, was applied. Geotechnical drill holes in 441 locations, consisting of 4,850 points of information, were used to determine the K values using the equation K = 2x10-6x HC0.5571. The K values, which were within the range of 10-8 and 10-5 m/s, were distributed into five alternative 3D distributions using Ordinary Kriging (OK) and Artificial Neural Network (ANN). The result of the ANN modeling showed that some of the K values, with log K varying from -10.51 m/s to -3.09 m/s, were outside the range of the observed K values. The OK modeling results of K values, with log K varying from -8.12 m/s to -5.75 m/s, were within the range of the observed K values. The ANN modeled K values were slightly more varied than the OK modeled values. The result of an alternative OK modeling was chosen to represent the existing data population of flow media because it fits well to the geological conditions.

Fuzzy-Based Prediction of Spatio-Temporal Distribution of Wet Muck in Block Cave Mine of PT Freeport Indonesia Lilik Eko Widodo; Eman Widijanto; Iftikhor Faadhilah; Wahyu Sunyoto
Journal of Engineering and Technological Sciences Vol. 50 No. 2 (2018)
Publisher : Institute for Research and Community Services, Institut Teknologi Bandung

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.5614/j.eng.technol.sci.2018.50.2.9

Mud rushes, or wet muck spills, are hydro-geotechnical challenges in block cave mines where wet muck spills out of drawpoints formed by the accumulation of fine materials and water in drawbells. The purpose of this paper is to share the results of the developement of an improved predictive tool that can be used to manage wet muck spills. The tool was developed based on the hybrid modeling of wet muck distribution using fuzzy logic and fuzzy number operations. The fuzzy logic operations were applied to model the spatial distribution of wet muck classes, providing the spatial model of drawpoint status based on five contributing factors, i.e. the height of draw, the water content, the grain size of the fine material, rainfall, and no-mucking days. The fuzzy number operations were used in accordance with the mass balance principle to estimate the temporal distribution of wet muck that forms a mud deposit consisting of fine materials and water in a drawbell. The mass balance principle was expressed using the fuzzy ordinary differential equation, including the uncertainty of joining variables. A wet muck spill event at the Deep Ore Zone (DOZ) block cave mine of PT Freeport Indonesia was utilized as a case study as well as to validate the proposed method. The fuzzy-based approach shows promising results in predicting wet muck spill events.

Physical Model of Vertical Water Movement Inside a Soil-Column Apparatus for Infiltration Study with A Two-Way Orientation Approach Reza Adhi Fajar; Gunawan Handayani; Sudarto Notosiswoyo; Lilik Eko Widodo; Tri Chandra Pamungkas
Journal of Engineering and Technological Sciences Vol. 51 No. 5 (2019)
Publisher : Institute for Research and Community Services, Institut Teknologi Bandung

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.5614/j.eng.technol.sci.2019.51.5.2

To improve the theory of Richard's equation, studying infiltration under free-draining conditions at the ground surface is necessary. Verification is required to clarify the physical model of water movement. The aim of this study was to describe multistage measurements of both the wetting and the drying front scheme of one-dimensional infiltration at laboratory scale. A soil-column infiltration apparatus was built consisting of a double acrylic wall, a sensor set and a light bulb. Acrylic was chosen as the material for the wall to minimize possible heat conduction on the wall side, which was wrapped in double insulation to achieve adiabatic condition. The following three main sensors were used and controlled by a microcontroller: water-content, pressure and temperature sensors. Meanwhile, the light bulb at the top of the apparatus was set to non-isothermal condition. The instrument was successfully built to describe vertical water movement. Slight modifications were carried out to ensure more precise observation. This resulted in the initiating of new shape interpretation based on the water-ponding measurement to refine the simplified pattern that was introduced by the conventional Green-Ampt theory.

Distribusi Vektor Aliran Air Tanah Dua Dimensi dalam Media Rekahan di Big Gossan, Tembagapura, Papua Lambok M. Hutasoit; Mudrik R. Daryono; Lilik Eko Widodo; Toddy Syaifullah
Jurnal Teknik Sipil Vol 17 No 2 (2010)
Publisher : Institut Teknologi Bandung

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.5614/jts.2010.17.2.2

Abstrak. PT. Freeport Indonesia (PTFI) berencana membuka tambang bawah tanah baru di Big Gossan dengan metode stope mine, yang menuntut daerah yang akan ditambang berada dalam kondisi kering. Di beberapa lokasi uji, air tanah keluar dari beberapa lubang stope dengan debit yang cukup mengganggu, tetapi di beberapa lokasi lainnya lubang berada dalam kondisi kering. Pemodelan hidrogeologi terdahulu, yang mengasumsikan bahwa akifer adalah media antar butir, tidak dapat menjawab variasi keberadaan air tanah tersebut. Akifer di daerah ini disusun oleh rekahan-rekahan. Dalam penelitian ini, dilakukan kembali pemodelan hidrogeologi dengan penekanan bahwa akifer adalah media rekahan dan pada titik-titik perpotongan antara sesar dan sungai terjadi peresapan. Dalam pemodelan ini, pertama-tama dilakukan analisis geometri dan orientasi rekahan. Hasil analisis digunakan untuk menghitung distribusi muka air tanah dengan Metode Gale dan konduktivitas hidrolik akifer dengan Metode Oda dkk. Kedua parameter tersebut digunakan untuk melakukan pemodelan hidrogeologi dalam dua dimensi, untuk mengetahui distribusi vektor aliran air tanah. Dari penelitian ini diperoleh bahwa konduktivitas hidrolik di daerah ini adalah heterogen, bukan homogen, seperti asumsi dalam pemodelan terdahulu. Hasil pemodelan hidrogeologi menunjukkan bahwa aliran air tanah terkonsentrasi disebelah barat laut dari Stope # 6.Abstract. PT. Freeport Indonesia (PTFI) is planning to open a new underground mine at Big Gossan by using stop mine method which requires dry mining area. In some pilot areas, groundwater flowed from some stope holes significantly, while in other areas, some holes were dry. Previous hydrogeologic modeling, assuming that aquifers were intergranular media, cannot answer the variation of the groundwater occurrence. The aquifers in the study area are composed of fractures. In this research, hydrogeology of the area is remodeled, stressing that the aquifers are fractured media and recharge takes place at the intersections of faults and rivers. In this modeling, fracture geometry and orientation are analysed first. The results are used to calculate groundwater table distribution by using Gale Method and hydraulic conductivity by using Oda et.al. Method. Both parameters are used to construct two dimensional hydrogeological modeling, to know distribution of groundwater flow vector in the research area. This research reveals that hydraulic conductivity in this area is heterogeneus, not homogeneous, as was assumed in the previous modeling. The hydrogeologic model shows that groundwater flow is concentrated to the northwest of Stope # 6.

PEMODELAN MATEMATIS METODE ELEMEN HINGGA UNTUK MENGHITUNG SUMBERDAYA BATUBARA DAERAH PONDOK LABU, CEKUNGAN KUTAI, KALIMANTAN TIMUR Mulyono Dwiantoro; Lilik Eko Widodo; Annisa Annisa
Geosapta Vol 3, No 2 (2017): Juli 2017
Publisher : Universitas Lambung Mangkurat

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.20527/jg.v3i2.3903

Tujuan penelitian yang telah dilakukan adalah menghitung sumberdaya batubara daerah Pondok Labu pada Cekungan Kutai di Kalimantan Timur. Metode pendekatan ilmiah yang digunakan adalah pemodelan matematis metode elemen hingga atau yang dikenal sebagai finite element method (FEM). Metode ini merupakan pendekatan matematis deterministik yang mencakup tiga tahapan pemodelan, yaitu: konseptual, matematika, dan numerik. Proses utama pada metode ini adalah diskritisasi yaitu membagi suatu elemen menjadi elemen-elemen yang lebih kecil untuk mempermudah dalam pengelolaanya sehingga dapat melibatkan atribut-atribut bobot atau nilai yang ingin diteliti di dalam batubara.Daerah penelitian terletak pada sayap Antiklin Busang yang memiliki arah lapisan antara N33-25oE dengan kedudukan landai antara 12-15o. Material yang diteliti adalah sebuah lapisan tunggal batubara yang diperoleh dari hasil 23 pengeboran eksplorasi dan singkapan yang muncul dipermukaan. Litologi yang dijumpai dari hasil pengeboran yaitu perulangan batupasir dengan batulempung, dan hadirnya lapisan batubara yang memiliki ketebalan bervariasi antara 0,45-1,5 m. Adapun untuk menghitung luas dan volume dengan cara melakukan diskritisasi pada lapisan batubara (roof dan floor) menjadi bagian-bagian yang lebih kecil yang disebut finite element. Perhitungan sumberdaya batubara dilakukan menggunakan batasan area pengaruh berjarak 200 meter dari titik terluar pemboran. Hasil penelitian menunjukkan bahwa volume sumberdaya batubara yang dihitung sebesar 835.843,35 m3.Kata-kata kunci: metode elemen hingga, sumberdaya batubara, Pondok Labu, Cekungan Kutai

Pengaruh Jarak Antar Drain Hole Terhadap Penurunan Muka Air Tanah pada Lereng Tambang Terbuka Batubara Rahmat Fadhilah; Lilik Eko Widodo; Irwan Iskandar
Journal of Science and Applicative Technology Vol 4 No 2 (2020): Journal of Science and Applicative Technology December Chapter
Publisher : Lembaga Penelitian dan Pengabdian Masyarakat (LPPM), Institut Teknologi Sumatera, Lampung Selatan, Lampung, Indonesia

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.35472/jsat.v4i2.369

The presence of groundwater on the slopes of the mine, which means that the slopes are saturated with water, will cause a decrease in slope stability. Drain hole is a method that can be applied to decrease groundwater level on a mine slope. This research was conducted to determine the effect of horizontal distance between drain holes on the mine slope on the decrease in groundwater level (groundwater drawdown). Groundwater flow simulation on the slopes of an open pit coal mine with 3 scenarios, without drain holes, 100 m horizontal space between drain holes, and 50 m horizontal space between drain holes, was carried out to answer the goal of this research. The results obtained from the simulation, the third scenario with a distance between drain holes of 50 m has the maximum result compared to the other two scenarios, which are the percentage of groundwater drawdown of 54.1% and groundwater discharge of 167.3 L/s. So it can be concluded that the denser the horizontal distance between the drain holes on the mine slope, the higher the groundwater drawdown on the slope.

Simulasi Respon Airtanah terhadap Kegiatan Dewatering pada Lokasi Penggalian Stasiun Bawah Tanah MRT A dan B di Kota Jakarta Pusat Absari, Hirundini Rustica; Widodo, Lilik Eko; Sadisun, Imam Achmad
Jurnal Ilmiah Geologi PANGEA Vol 11, No 1 (2024): Jurnal Ilmiah Geologi Pangea
Publisher : PROGRAM STUDI TEKNIK GEOLOGI FAKULTAS TEKNOLOGI MINERAL UPN VETERAN YOGYAKARTA

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.31315/jigp.v11i1.12703

Kegiatan penggalian dan dewatering yang dilakukan di kawasan perkotaan menghadapi tantangan akibat keberadaan airtanah. Airtanah yang tidak dikontrol dapat mengganggu kestabilan bangunan-bangunan bersejarah dan penting yang berada di sekitar lokasi penggalian. Lokasi kegiatan penggalian dan dewatering berada di Kota Jakarta Pusat, Provinsi DKI Jakarta, yang dilakukan untuk konstruksi dua stasiun bawah tanah MRT yang berjarak 800 m. Lokasi ini berada di Cekungan Airtanah Jakarta dengan litologi penyusun berupa endapan kipas aluvium dengan material butir berukuran lempung hingga pasir sendang berumur Kuarter. Kegiatan dewatering dilakukan dengan menggunakan sumur pelepasan tekanan (pressure relief well) sebanyak 46 sumur di Stasiun Bawah Tanah A dan 29 sumur di Stasiun Bawah Tanah B dengan kapasitas 4,15 m³/s per sumur . Simulasi airtanah dilakukan menggunakan Softwater Visual Modflow dengan metode numerik beda hingga berdasarkan beberapa asumsi untuk menyederhanakan pembuatan model airtanah. Pemantauan respon airtanah dilakukan dengan pengamatan terhadap perubahan head dan drawdown selama 1186 hari. Pada lokasi Stasiun Bawah Tanah A, terjadi penurunan head (drawdown) sebesar 3,1 m, sedangkan pada Stasiun Bawah Tanah B terjadi drawdown sebesar 5,5 m. Pengaruh dewatering dapat terlihat hingga jarak 550 m dengan drawdown sebesar 1- 8 cm.

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