Sains Malaysiana 36(2): 105-116 (2007)

 

Tinjauan Awal Potensi Ketidakstabilan Cerun dan Cirian

Fiziko-Kimia Tanah di Cameron Highlands, Pahang

(Preliminary Survey on Potential Slope Instability and Soil Physico-Chemical

Characteristic in Cameron Highland, Pahang)

 

 

Zulfahmi Ali Rahman, Sahibin Abd. Rahim & Wan Muhd Razi Idris

Program Sains Sekitaran, Pusat Pengajian Sains Sekitaran dan Sumber Alam

Fakulti Sains dan Teknologi, Universiti Kebangsaan Malaysia

43600 Bangi Selangor D.E., Malaysia

 

Jasni Yaakob

Institut Alam Sekitar dan Pembangunan (LESTARI)

Universiti Kebangsaan Malaysia, 43600 Bangi Selangor D.E.

Malaysia

 

Diserahkan: 29 Januari 200 7 / Diterima: 16 Februari 2007

 

 

ABSTRAK

Secara geologi, kawasan Cameron Highland terdiri daripada batuan granit batolit  yang merejah ke dalam batuan sedimen yang lebih tua. Rejahan jasad igneus asidik ini menyebabkan pembentukan batuan meta-sedimen dan batuan metamorfik lain sebagai sisa bumbung. Sekis sering ditemui telah mengalami luluhawa tinggi hingga sepenuhnya, berwarna kelabu cerah hingga gelap dengan butiran halus hingga sederhana dan struktur foliasi yang ketara. Manakala batuan granit mengandungi mineral kuarza, felspar dan butiran biotit dan/atau turmalin. Kebanyakan cerun potongan jalan raya yang dibina merentasi jasad batuan ini dan survei ketidakstabilan cerun dilakukan berdasarkan jenis, geometri dan cirian fiziko-kimia tanah cerun. Hasil cerapan lapangan menunjukkan bahawa jenis cerun yang gagal adalah jenis cerun tanah yang terdiri daripada jenis gelinciran cetek dan dalam. Antara faktor yang menyumbang kepada ketidakstabilan cerun adalah geometri cerun seperti cerun yang tinggi dan sudut muka cerun yang curam, sifat keperoian tanah pada cerun dan kekurangan litupan vegetasi permukaan. Ini menyebabkan permukaan cerun terdedah kepada hentaman terus hujan. Kesan daripada air larian permukaan juga menyebabkan pembentukan alur-alur hakisan pada muka cerun tanah. Sifat fiziko-kimia bahan cerun (tanah) seperti taburan saiz partikel, pH, kandungan ferum oksida, bahan organik, kandungan air, ketumpatan pukal dan sebenar serta keporosan juga didapati memainkan peranan sebagai faktor yang dalaman dalam mempengaruhi kestabilan cerun tertentu yang dikaji. Julat pH tanah yang rendah (sifat asidik) pada semua cerun mengurangkan kandungan ferum oksida dalam tanah yang bertindak sebagai bahan penyimen tanah. Ini menyebabkan agregatan tanah menjadi lemah dan mudah terhakis. 

Kata kunci: Ketidakstabilan cerun; gelinciran; geometri; luluhawa 

 

 

ABSTRACT

Geologically Cameron Highlands was formed by a granite batholith intruding into the older sedimentary rocks. Intrusion of this acidic igneous rock formed metasedimentary rocks and other metamorphic rocks as roof pendants. The schist had been highly weathered, coloured bright grey to dark grey having fine to medium size grains with an obvious foliation. Meanwhile the granitic rock is composed of quartz, feldspar and biotite and/or tourmaline grains. Most of the road slopes cut across the granite body and slope instability survey was carried out based on type of failure, geometry and physico-chemical properties of soil slopes. Field observations showed that most of the failed slopes were soil slopes, and the slip that occurred were either shallow slip or deep slide types. Among the factors that influenced slope instability were slope geometry such as slope height and steep slope gradient, friable features of the weathering profile and the lack of surface vegetation cover. This rendered the slope surface exposed to the direct raindrop impact. Surface water run-off has also caused the development of erosion gullies on soil slope surface. Physico-chemical properties of slope material such as particle size distribution, pH, organic matter content, iron oxide content, water content, true and bulk density, and porosity were also influential in slope stability of the slopes investigated. Low soil pH (acidic) of all the slopes examined decreased iron oxide content of soil which acted as a cementing agent to soil aggregates. This has caused the soil aggregate to become weaker and easier eroded.

 

Keywords: Slope instability; slide; geometry; weathering

 

 

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