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Beneath the Surface: Identifying Subsurface Caves in "Gua Pandan" Using Integrated Electrical Profiling Method Antosia, Risky Martin; Akbar, Hendra Hidayat; Santoso, Nono Agus; Putri, Intan Andriani; Farishi, Bilal Al; Natalia, Happy Christin
POSITRON Vol 13, No 1 (2023): Vol. 13 No. 1 Edition
Publisher : Fakultas Matematika dan Ilmu Pengetahuan Alam, Univetsitas Tanjungpura

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.26418/positron.v13i1.63558

Abstract

One of the geopark tourism areas in East Lampung Regency, "Gua Pandan," has run into rock subsidence on the surface. As part of the subsidence prevention, indirect electrical methods between resistivity and chargeability profiling were applied to identify the presence of a subsurface cave in the study area. Two measurement lines were carried out with Wenner Alpha and Wenner Schlumberger arrays. Because the depth target is shallow (approximately 10 m) and to obtain a better resolution, each line has a stretch length of 70 m and 2 m electrode spacing. A line was measured over a known underground cave to produce a desired outcome, and the other was in an area with no cavities. Based on the results from each profile of resistivity and chargeability, an air-filled target has a value of over 5,000  and under 6 ms, respectively. Then, integrated processing of both methods generated a metal factor (MF) profile to view the presence and estimated shape of the cave/ cavities. The result represents that an MF value under 1.5 ms/Ωm is a cavity, and solid rock is over 1.5 ms/Ωm. Also, the MF level from both configurations delineates a similar section. However, a modest difference occurs in estimating the cavity shape geometry,  for Wenner Apha and  for Wenner Schlumberger. Furthermore, this study can be an initial step in safety assessment in the area.
Mineralogical Characteristics and Critical Stress Variation in Rock Samples from Bukit Kunyit, Bandar Lampung Setiawan, Muhamad Ragil; Hilman, Zaki; Haqiqi, Rian Bayu; Farishi, Bilal Al
Journal of Science and Applicative Technology Vol. 9 No. 1 (2025): Journal of Science and Applicative Technology June 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.v9i1.2026

Abstract

Mineralogy is essential for understanding rock formation processes and their physical properties, including critical stress. Critical stress values can be estimated using unconfined compressive strength (UCS) measurements, which depend on the modulus values of the minerals present. This study explores the mineralogical characteristics of rock samples from Bukit Kunyit, Bandar Lampung City, and Lampung through X-ray diffraction (XRD) and petrographic analysis. Macroscopic observations revealed two visually distinct rock samples: one with a bright color (Sample 1) and another with a darker hue (Sample 2). Despite these color differences, XRD analysis showed that both samples have the same mineral composition, including Anorthoclase, Cristobalite, Tridymite, and Muscovite, indicating a felsic (silica-rich) nature. Differences were noted in the crystallographic forms of Muscovite and Quartz content, with Sample 2 having a higher Quartz concentration. These mineralogical variations correlate with the observed differences in critical stress, with Sample 1 exhibiting a lower critical stress (20.98 MPa) than Sample 2 (35.05 MPa).