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Sains Malaysiana 54(6)(2025): 1465-1475
http://doi.org/10.17576/jsm-2025-5406-03
Utilizing Gravity Surveys
for Subsurface Feature Identification in Foundation Planning
(Menggunakan Tinjauan
Graviti untuk Pengecaman Ciri Subpermukaan dalam Perancangan Asas)
NORDIANA MOHD MUZTAZA1,6,*, THANATH
GOPALAN2, NUR AMANINA MAZLAN2, JAMALUDIN OTHMAN3,
NAZRIN RAHMAN4, NAJMIAH ROSLI4, ROSLI SAAD1,4,6, FARID
NAJMI ROSLI1,4, ATHIRAH ROSLI4 & YASIR
BASHIR5
1School
of Physics, Universiti Sains Malaysia, 11800 USM, Pulau Pinang, Malaysia
2Mass Rapid Transit Corporation Sdn Bhd Headquarters, Tingkat
5, Menara I & P1, 46 Jalan Dungun, Bukit Damansara, 50490 Kuala Lumpur,
Malaysia
3SubMAP
Geophysical Services Sdn. Bhd, A-5-10, Empire Tower, SS16/1, 40750 Subang Jaya,
Selangor, Malaysia
4Global
GeoExperts Sdn. Bhd., 737-6-5, Kompleks Sri Sg Nibong, Jalan Sultan Azlan Shah,
11900 Bayan Lepas, Pulau Pinang, Malaysia
5Geophysical
Engineering, Istanbul Technical University, Istanbul, Turkey
6Pusat
Geokejuruteraan Tropika (GEOTROPIK), Aras 2 Blok D03, Faculty of Civil
Engineering, Universiti Teknologi Malaysia, 81310 Johor Bahru, Johor, Malaysia
Received:
12 June 2024/Accepted: 28 March 2025
Abstract
Understanding the distribution and
extent of solution features such as cavities and pinnacles in limestone bedrock
is crucial for anticipating potential challenges and planning appropriate
foundation solutions. This
study employed microgravity surveying to complement available borehole data and
map karst features, particularly cavities, within the limestone bedrock. The survey was conducted on a 5 m ×
5 m grid interval, establishing a total of 91 stations. Reduced Bouguer and
residual anomalies were contoured and plotted using the GEOSOFT Oasis Montaj
Mapping system. Anomalies of interest were further analyzed through 2-D gravity
modeling using PotentQ software to determine the dimensions of the causative
bodies. The survey results, presented as Bouguer, residual, and Bouguer anomaly
horizontal gradient maps, showed a small range of gravity values (-9.24 to
-9.10 mGal), indicating minimal variation in limestone bedrock topography.
Gravity highs were associated with shallow limestone bedrock, while isolated gravity
lows suggested the presence of cavities. Horizontal gradient maps highlighted
peaks corresponding to the edges of these cavities and potential channel-like
features. Borehole data corroborated the microgravity findings, with bedrock
encountered at depths between 9.6 m and 12.3 m indicating deeper bedrock
towards the south. The 2-D gravity modeling suggested a sediment-filled cavity
approximately 7 m thick and 15 m wide in an east-west orientation, aligning
well with borehole data. The combined use of borehole data and microgravity
surveying proved effective in characterizing subsurface karst features,
providing valuable insights for foundation planning leading to safer and more efficient
construction practices.
Keywords: Anomaly;
Bouguer; cavities; limestone; microgravity
Abstrak
Pengetahuan tentang
taburan dan ciri larutan seperti rongga dan puncak batu kapur adalah penting
untuk meramal potensi cabaran dan merancang pembinaan tapak yang sesuai. Kajian
ini menggunakan survei mikrograviti untuk melengkapkan data lubang bor yang
sedia ada dan memetakan ciri karst, khususnya rongga dalam batuan kapur. Tinjauan
dilakukan dengan sela grid 5 m × 5 m, berjumlah 91 stesen. Anomali
Bouguer yang dikurangkan dan baki digambarkan menggunakan sistem pemetaan
GEOSOFT Oasis Montaj. Anomali yang menarik dianalisis lebih lanjut melalui
pemodelan graviti 2-D menggunakan perisian PotentQ untuk menentukan dimensi jasad
yang menjadi punca. Keputusan survei yang diketengahkan sebagai peta anjakan
Bouguer, baki dan gradien mendatar anjakan Bouguer mendedahkan julat kecil dengan
nilai graviti (-9.24 hingga -9.10 mGal), menunjukkan variasi minimum dalam
topografi batuan kapur. Anjakan graviti tinggi dikaitkan dengan batuan kapur
cetek, manakala anjakan graviti rendah menunjukkan kehadiran rongga. Peta
gradien mendatar menunjukkan puncak yang sepadan dengan tepi rongga ini dan
ciri potensi berbentuk saluran. Data lubang bor mengesahkan penemuan
mikrograviti dengan batuan kapur dijumpai pada kedalaman antara 9.6 m dan 12.3
m menunjukkan batuan kapur yang lebih dalam ke arah selatan. Pemodelan graviti
2-D menyarankan keberadaan rongga berisi endapan dengan ketebalan kira-kira 7 m
dan lebar 15 m dengan orientasi timur-barat, sejajar dengan data lubang bor. Penggunaan
data lubang bor dan survei mikrograviti terbukti berkesan dalam pencirian karst
di bawah permukaan, memberikan maklumat penting untuk perancangan tapak yang
lebih selamat dan cekap dalam amalan pembinaan.
Kata kunci: Anomali;
batu kapur; Bouguer; mikrograviti; rongga
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*Corresponding
author; email: mmnordiana@usm.my
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