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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.

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.

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.

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.

Estimating Groundwater Inflow to The Underground Mine Works using a 3D Groundwater Model at Vein Kubang Cicau, UBPE Pongkor Naiborhu, Kory Yohana Adinda; Anggayana, Komang; Widodo, Lilik Eko; Wibowo, Aryo Prawoto
Indonesian Journal on Geoscience Vol. 11 No. 3 (2024)
Publisher : Geological Agency

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.17014/ijog.11.3.423-435

Estimating groundwater inflow to underground mines is essential for ensuring that mining activities can be conducted safely and continuously. Research conducted at UBPE Pongkor indicates that the veins have the fault connectivity with the Kubang Cicau vein showing potential for deeper mining, while other veins are expected to become exhausted. As the result, the Kubang Cicau vein will likely be at a lower elevation in the future. Planning decisions regarding groundwater control measures, such as dewatering, can be made in advance, contributing to a more efficient assessment of the economic feasibility of mining development. Groundwater modeling using MODFLOW software predicted a maximum groundwater discharge of 55 L/s. To address the model uncertainty, a sensitivity analysis was performed by increasing the hydraulic conductivity parameter by two order of magnitude, as this value significantly affects groundwater inflow. Conversely, decreasing the hydraulic conductivity by two order resulted in a new discharge estimate of 87 L/s. In the worst-case scenario, with the highest specific storage values, the inflow increased to 76 L/s. This demonstrates that although changes in specific storage have a notable effect on groundwater inflows, the impact is less pronounced compared to the changes in hydraulic conductivity. Nonetheless, Ss remains a key parameter, particularly in transient simulations where storage plays a more significant role in the system response to changes in water levels.

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.

Fault Surface Rupture Modeling Using Particle Image Velocimetry Analysis of Analog Sandbox Model Furqan, Terry Alfa; Sapiie, Benyamin; Natawidjaja, Danny Hilman; Widodo, Lilik Eko; Rudyawan, Alfend; Hadiana, Meli
Journal of Engineering and Technological Sciences Vol. 56 No. 1 (2024)
Publisher : Directorate 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.2024.56.1.10

This study investigated the correlation between fault kinematics, surficial displacement, and surface rupture geometry patterns between earthquake cycles using particle image velocimetry (PIV) analysis of an analogue sandbox modeling that mimics InSAR observations. The research explored various fault systems, including reverse, normal, and strike-slip faults, through controlled sandbox experiments. The fault surface rupture zone manifests itself due to strain accumulation between two mobile blocks. The displacement magnitude is most pronounced on the surface and is absorbed by the section above the hanging wall or moving block. During fault surface rupture formation, the leading edge of the surface movement consistently extends beyond the anticipated fault surface rupture zone and retreats upon full fault surface rupture development. Subsequently, the distribution of the surface movement is sharply confined by the established fault surface rupture. The key findings of this study underscore the potential of PIV of sandbox modeling for studying fault surface rupture geometry and its development, providing insight into seismic processes. Overall, this work contributes to advancing our knowledge of seismic phenomena and improving strategies for earthquake prediction and mitigation.

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