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Journal of Applied Geology
Published by Universitas Gadjah Mada
ISSN : 25022822     EISSN : 25022822     DOI : https://doi.org/10.22146
Core Subject : Science, Social, Engineering,
Civil Engineering, Building, Construction & Architecture Earth & Planetary Sciences Energy Engineering Environmental Science
Journal of Applied Geology – JAG focuses on the applied geology and geosciences with its key objective particularly emphasis on application of basic geological knowledge for addressing environmental, engineering, and geo-hazards problems. The subject covers variety of topics including geodynamics, sedimentology and stratigraphy, volcanology, engineering geology, environmental geology, hydrogeology, geo-hazard and mitigation, mineral resources, energy resources, medical geology, geo-archaeology, as well as applied geophysics and geodesy.
Arjuna Subject : Ilmu Bumi dan Planet (semua kategori) - Geologi
Articles 6 Documents
 1 
Search results for , issue "Vol 8, No 1 (2023)" : 6 Documents clear
Stability Analysis of Saka DAM Diversion Tunnel Portal Febrie Maulana Fajrin; Subagyo Pramumijoyo; I Gde Budi Indrawan
Journal of Applied Geology Vol 8, No 1 (2023)
Publisher : Geological Engineering Department Universitas Gadjah Mada

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.22146/jag.57578

Abstract

The Saka Dam has a channel in the form of a diversion tunnel. This paper presents the results of rock mass characterization using the Geological Strength Index (GSI) classification and evaluation of the stability of the tunnel portal slope with earthquake loads using numerical methods. Based on the GSI classification, the Saka Dam tunnel portal slope is composed of rock masses that are poor quality, fair, and good. The calculation results show the Saka Dam can experience earthquake loads with an acceleration value of 0.4g. Earthquake loads can cause a decrease in the safety value (SRF) of the tunnel portal slope based on the results of numerical analysis. SRF value of natural portal slope without earthquake effect is 10.23 (inlet) and 1.5 (outlet). SRF value of the design slope portal without earthquake effect is 6.64 (inlet) and 1.76 (outlet), whereas if the earthquake effect is taken into account the SRF value obtained is 20.31 (inlet) and 0.99 (outlet). This shows that the condition of the natural portal slope and the portal slope design planner section of the Saka Dam inlet diversion tunnel is in the safe category. Meanwhile, for the portal slope excavated from the outlet section, modification is needed to obtain a safe slope condition. The results of the modified geometry of the slopes at the outlet section resulted in an SRF value of 1.47 which indicates the slope is stable 
Identification of Permeable Structures and Heat Source in the Geothermal Working Area of Galunggung Volcano and the Heat Source Connectivity to the Karaha-Cakrabuana Area Using Gravity Data Leo Agung Prabowo; Salahuddin Husein; Sismanto Sismanto
Journal of Applied Geology Vol 8, No 1 (2023)
Publisher : Geological Engineering Department Universitas Gadjah Mada

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.22146/jag.60835

Abstract

Galunggung volcano area is a geothermal concession area that adjacent with Karaha-Cakrabuana concession area with a distance around 1 km. Indonesian Government planning to build power plant in 2025 so additional research needed to support the plan. Gravity survey could help in identifying permeable structure (fault) as well as heat source to a certain depth. The results of data processing showed the presence of faults seen on the FHD, SVD, and ABL residual maps, while for heat sources it was shown from the closed contour patterns on the ABL, residual, and regional maps. Derivative analysis in strengthens the position and type of fault from the match between the maximum FHD value and zero SVD value. From these results, identified the existence of three faults in the study area and were all identified as normal faults. 3D modelling gave a picture of density contrast in research area. From the section profile that pass through Galunggung and Telaga Bodas crater, heat source was interpreted as density with value 2.8 – 3.0 gr/cm3 and marked by orange to red color that coincide below Galunggung crater and continoued to Talaga Bodas crater at depths below -3000 masl. This indicate that both concession area was connected.
Determination of Overpressure Zone and Its Mechanism in Baong Formation of the "Y" Field in North Sumatera Basin Andrea Hasbullah; Hendra Amijaya; Jarot Setyowiyoto
Journal of Applied Geology Vol 8, No 1 (2023)
Publisher : Geological Engineering Department Universitas Gadjah Mada

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.22146/jag.63556

Abstract

The “Y” Field is one of the offshore areas in the North Sumatra Basin which is believed to have an important role in hydrocarbon exploration in the future. The North Sumatra Basin is known as an area that has high overpressure conditions and sometimes overpredicts in determining the amount of overpressure, especially in the Baong Formation. The purpose of this research is to determine the top and bottom overpressure zones, to know the vertical distribution of overpressure, and to find the main factors causing the overpressure in the Baong Formation.The data used in this study were 5 wells which have wireline log data, formation pressure data, leak of test, final well reports, mud logs, as well as 29 lines of 2D seismic data and 1 3D seismic data. The method used in this study was the Eaton method to determine pore pressure whereas the cross-plot wireline log method, the AI (acoustic impedance) inversion method and the stacking velocity were used to determine pore pressure.The study indicated that the overpressure zone is located in the Baong Formation at 1650 - 2108 m depth with a pore pressure of around 2891.70 - 3580 psi.  The overpressure is caused by loading mechanism, namely disequilibrium compaction. This is influenced by the thickness of the formation above Baong Formation.
Evaluation of Engineering Geological Conditions for Slope Stability Analysis of Diversion Tunnel Portal of Jlantah Dam, Karanganyar, Central Java Yayi Ismanda; I Gde Budi Indrawan; Heru Hendrayana
Journal of Applied Geology Vol 8, No 1 (2023)
Publisher : Geological Engineering Department Universitas Gadjah Mada

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.22146/jag.72438

Abstract

This paper presents the research results carried out to analyze the slope stability of the diversion tunnel portal of Jlantah Dam based on the quality of the rock mass. The classification of the rock mass quality at the tunnel location refers to the Geological Strength Index (GSI) method while the analysis of portal slope stability is modelled numerically with the element method using Phase2 software. The modelling of the tunnel portal slope design with and without earthquake load was carried out to obtain the safety factor (SF) value. The results showed that the study area consists of residual soil, andesite breccia and lapilli tuff rocks with rock mass quality based on the GSI value ranging from poor to fair. The inlet portal slope is composed of rocks that have poor and fair mass quality while the inlet section is composed of rocks that have poor mass quality. The SF value>1.3 for conditions without earthquake effect was achieved on slope design 1V:1.5H and SF value>1.1 for conditions with earthquake effect was achieved on slope design 1V:2H. The SRF value at the portal outlet location is greater than the SRF value at the portal inlet location for the same slope design conditions indicating that the rock mass quality at the portal outlet location is better than the rock mass quality at the portal inlet location.
Cooling history (from magma ascent to lava extrusion) of the Watuadeg pillow lava, Berbah, Yogyakarta, Indonesia Indranova Suhendro; Agung Harijoko; Nugroho Imam Setiawan; Haryo Edi Wibowo
Journal of Applied Geology Vol 8, No 1 (2023)
Publisher : Geological Engineering Department Universitas Gadjah Mada

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.22146/jag.73942

Abstract

The Watuadeg pillow lava (WPL) is known as one of the most famous pillow lava outcrops in Yogyakarta, Indonesia, and its origin has been attributed to rapid-cooling process of subaqueous lava extrusion. However, there is no quantitative evidence that implies such hypotheses. Therefore, this study aims to reduce such a gap by revealing the cooling times (t) of WPL on the basis of a quantitative approach. In particular, we measured the size distribution (CSD) and number density (MND) of plagioclase microlites from the core, medial, and marginal (rim) domains of WPL. We found that the CSD slope significantly increases towards marginal zones, namely 30.4ᵒ for the core, 53.4ᵒ for the medial, and 228.1ᵒ for the rim. Because CSD slope is inversely proportional to cooling time ( ), by assuming a typical plagioclase microlite growth rate (G) of 1×107 mm/s, it is therefore inferred that the rim experienced the fastest cooling time (±12.1 hours), followed by the medial and core ((±52.0 and 91.4 hours, respectively). The fact that MNDs value increases toward the marginal zones also does not deny this idea (0.3×1016 m-3 for the core, 1.4×1016 m-3 for the medial, and 2.4×1016 m-3 for the rim), as higher MND with the domination of acicular-spherulitic habit represents a higher degree of undercooling. Because microlite is syn-eruptive product, our estimation represents the cooling time of magma since it migrated from the reservoir to the surface.
Source Rock Quality and 1D Maturity Model in Pendalian Sub-basin, Central Sumatra Basin Putri Dwi Afifah; Hendra Amijaya; Sarju Winardi; Widi Atmoko
Journal of Applied Geology Vol 8, No 1 (2023)
Publisher : Geological Engineering Department Universitas Gadjah Mada

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.22146/jag.78104

Abstract

Pematang Formation is well known as the main source rock in the Central Sumatra Basin (Mazied et al., 2008). The formation which acts as source rock has been studied thoroughly in the central and eastern parts of the basin, but research regarding source rock in the western part of the basin, which is the study area, is very limited. This paper aims to define the quality of source rock from a geochemical view through the determination of organic content quantity based on the Total Organic Carbon (TOC) data, determining the type of kerogen, and thermal maturity of the source rock according to the values of Tmax and Vitrinite Reflectance (%Ro). Burial history and thermal maturity models (1D basin modeling) were also constructed to understand the timing of hydrocarbon generation. The results show that Pematang Formation among Sihapas and Telisa Formation has good organic content with TOC ranging from 0.2 to 42.48 wt%, and the maturity parameters indicate that the Pematang Formation has reached the mature stage. Both formations are dominated by Type II kerogen. 1D modeling of the SHT-1 Well indicates that the Pematang Formation is currently in the oil maturity window starting from early oil to main oil at 20.61 Ma, but the model of the SMB-1 Well has not reached the oil maturity window. Tectonic activity is estimated to have a significant effect on this difference when the uplift activity of Bukit Barisan in the Middle Miocene increased the maturity in the northwest, but the inversion that occurred in the Late Miocene resulted in uplift and erosion of young sediments, thus lowering the temperature in some area.

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