Sains Malaysiana 40(4)(2011): 293–300

Engineering Geological Properties of Oil-Contaminated Granitic and Metasedimentary Soils

(Sifat Geologi Kejuruteraan Tanih Granit dan Metasedimen Tercemar Minyak)

Zulfahmi Ali Rahman*, UmarHamzah & Noorulakma Binti Ahmad

School of Environmental & Natural Resource Sciences, Faculty of Science and Technology

Universiti Kebangsaan Malaysia, 43600 Bangi, Selangor D.E., Malaysia

Diserahkan: 9 Disember 2009 / Diterima: 21 Jun 2010

ABSTRACT

Hydrocarbon is a light-non aqueous phase liquid or known as LNAPL. It poses environmental hazard if accidentally spilled out into the soil and water systems as a result of its insoluble nature in water. LNAPL component infiltrates into soil through pore spaces and afloat at the top of groundwater level. Some of this hydrocarbon would trap and clog within the voids, difficult to remove and costly to clean. The occurence of hydrocarbon in the soil definitely degraded the behaviour of soils in terms of engineering properties. This study aimed to investigate the engineering properties of oil-contaminated soil for two different residual soils originally developed from in-situ weathering of granitic and metasedimentary rocks. The physical characterisations of the soil were determined including particle size distribution, specific gravity test and x-ray diffraction (XRD). The engineering parameters for the contaminated and uncontaminated soils were Atterberg limits, compaction and soil shear strength (UU tests). The amounts of hydrocarbon added to soil were varied at 0%, 4%, 8%, 12% and 16% of dried weigth of soil samples. The results from the particle size distribution analysis showed that residual soil from granitic rock comprises of 38% sand, 33% silt and 4% clay while metasedimentary soil consists of 4% sand, 43% silt dan 29% clay. The mean values of specific gravity for the granitic and metasedimentary soils were 2.56 and 2.61, respectively. The types of minerals present in granitic soil sample were quartz, kaolinite and gibbsite while metasedimentary soil consists of quartz and kaolinite. The Atterberg limits value decreased as a result of increasing amount of added hydrocarbon into the soil. A similar behaviouir was observed with the values of maximum dry density and optimum water content with increasing hydrocarbon content. The overall unconsolidated undrained shear strength, Cu showed a decreasing trend with the increase in hydrocarbon content.

Keywords: Contaminated soil; engineering parameter; hydrocarbon; LNAPL

ABSTRAK

Hidrokarbon adalah bahan cecair ringan tidak larut atau dikenali sebagai LNAPL. Ia menyumbang kepada hazad persekitaran jika tertumpah secara tidak sengaja ke dalam sistem tanah dan air kesan daripada sifatnya yang tidak larut air. Komponen LNAPL meresap ke dalam tanah melalui ruang rongga dan terapung di permukaan paras air tanah. Sebahagian hidrokarbon mungkin terperangkap dan tersumbat di dalam rongga, sukar untuk dikeluarkan dan memerlukan kos bagi membersihkannya. Kehadiran hidrokarbon di dalam tanah pasti menyusutkan sifat tanah daripada segi cirian kejuruteraan. Kajian ini bertujuan untuk menyiasat sifat-sifat kejuruteraan tanah tercemar minyak bagi dua jenis tanah baki yang asalnya terbentuk secara luluhawa in-situ batuan granit dan batuan metasedimen. Pencirian tanah yang ditentukan termasuk taburan saiz partikel, graviti spesifik dan pembelauan sinar-x (XRD). Parameter-paramter kejuruteraan bagi tanah tercemar dan tidak tercemar adalah had-had Atterberg, pemadatan dan kekuatan ricih (ujian UU). Jumlah hidrokarbon yang ditambah ke atas tanah bebrbeza-beza pada 0%, 4%, 8%, 12% dan 16% bagi berta kering sampel-sampel tanah. Hasil daripada analisi taburan saiz partikel menunjukkan tanah baki daripada batuan granit terdiri daripada 38% pasir, 33% lodak dan 4% lempung manakala tanah metasedimen pulam terdiri daripada 4% pasir, 43% lodak dan 29% lempung. Nilai-nilai purata graviti spesifik bagi tanah granit dan metasedimen masing-masing adalah 2.56 dan 2.61. Jenis mineral yang hadir bagi tanah granit adalah kuarza, kaolinit dan gibsit manakala tanah metsedimen terdiri daripada kuarza dan kaolinit. Nilai-nilai Atterberg menyusut akibat peningkatan jumlah hidrokarbon yang ditambah kepada tanah. Perlakuan yang sama diperhatikan bagi nilai-nilai ketumpatan kering maksimum dan kandungan air optimum dengan peningkatan kandungan hidrokarbon. Kekuatan ricih keseluruhan tidak terkukuh dan tidak bersalir, Cu menunjukkan corak penyusutan dengan peningkatan kandungan hidrokarbon.

Kata kunci: Hidrokarbon; LNAPL; parameter kejuruteraan; tanah tercemar

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*Pengarang untuk surat-menyurat; email: zarah1970@ukm.my