Sains Malaysiana 40(6)(2011): 577–585

Pull-Out and Tensile Strength Properties of Two Selected Tropical Trees

(Ciri-Ciri Tarikan-Keluar dan Kekuatan Tegangan Dua Pokok Tropika Terpilih)

Normaniza Osman* & Mohamad Nordin Abdullah

Institut Sains Biologi, Fakulti Sains, Universiti Malaya

50603 Kuala Lumpur, Malaysia

Che Hassandi Abdullah

Unit Penyelidikan dan Perkembangan, Cawangan Kejuruteraan Cerun

Tingkat 12, Blok F, Ibu Pejabat JKR, Jalan Sultan Salahuddin

50582 Kuala Lumpur, Malaysia

Diserahkan: 21 Mei 2010 / Diterima: 3 November 2010

ABSTRACT

A bioengineering technique is gradually being used as an alternative for slope stabilisation design. The effect of vegetation on soil strength, particularly in terms of root reinforcement aspects has therefore become a major interest. However, there is a lack of documentation on the root mechanical properties available especially in Malaysia. In this study, both pull-out and tensile strength of two tropical trees namely Leucaena leucocephala and Acacia mangium were investigated on different stem sizes. L. leucocephala performs the higher pullout strength than A. mangium. The results also show that pullout resistance is much affected by the root than the shoot profiles. In terms of tensile strength, the tensile strength decreases with increasing root diameter, implying the finer root diameter contribute to the higher tensile strength. In both parameters, L. leucocephala exhibits the highest value. The study suggests that L. leucocephala has an added value as a good potential slope plant for slope stabilization work as it exhibits outstanding root mechanical properties. Interestingly, the results also showed that the pullout force was much affected by the tensile strength. It can be concluded that some root and shoot properties do have a great impact on root mechanical properties such as tensile and pullout strengths.

Keywords: Lateral roots; pull-out; root morphologies; shoot morphologies; tap roots

ABSTRAK

Penggunaan kaedah bio-kejuruteraan semakin mendapat tempat sebagai alternatif dalam merekabentuk penstabilan cerun. Kesan vegetasi terhadap kekuatan tanah, terutamanya dalam aspek pengukuhan akar telah menjadi tumpuan utama. Walau bagaimanapun, terdapat kekurangan dalam mendokumentasikan ciri-ciri mekanikal akar terutamanya di Malaysia. Di dalam kajian ini, kedua-dua tarikan-keluar dan kekuatan tegangan bagi dua pokok tropika iaitu Leucaena leucocephala dan Acacia mangium dikaji pada saiz batang yang berbeza. L. leucocephala menunjukkan kekuatan tarikan-keluar yang lebih tinggi daripada A. mangium. Keputusan juga menunjukkan bahawa rintangan tarikan-keluar lebih dipengaruhi profil akar berbanding pucuk. Bagi kekuatan tegangan pula, kekuatan tegangan berkurang dengan peningkatan diameter akar, mengandaikan yang diameter akar yang halus menyumbang kepada kekuatan tegangan yang lebih. Bagi kedua-dua parameter, L. leucocephala mempunyai nilai yang paling tinggi. Kajian ini mencadangkan L. leucocephala mempunyai nilai tambah sebagai tumbuhan yang berpotensi untuk menstabilkan cerun di mana ia menunjukkan ciri-ciri akar yang menakjubkan. Menariknya, keputusan juga menunjukkan bahawa daya tarikan-keluar turut dipengaruhi oleh kekuatan tegangan. Dapat disimpulkan bahawa beberapa ciri akar dan pucuk mempunyai impak yang besar terhadap ciri mekanikal akar seperti tegangan dan kekuatan tarikan-keluar.

Kata kunci: Akar-akar lateral; akar-akar tunjang; morfologi akar; morfologi pucuk; tarikan-keluar

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*Pengarang untuk surat-menyurat; email: normaniza@um.edu.my