Sains Malaysiana 43(10)(2014): 1477–1484

Rainfall Infiltration through Unsaturated Layered Soil Column

(Penyusupan Air Hujan melalui Tanah Tak Tepu pada Tiang Tanah)

ANIZA IBRAHIM^1,2, MUHAMMAD MUKHLISIN^1,3* & OTHMAN JAAFAR¹

¹Department of Civil and Structural Engineering, Universiti Kebangsaan Malaysia

43600 Bangi, Selangor, Malaysia

²Department of Civil Engineering, Faculty of Engineering, Universiti Pertahanan Nasional Malaysia, Kem Sungai Besi, 57000 Kuala Lumpur, Malaysia

³Department of Civil Engineering, Polytechnic Negeri Semarang, Indonesia

Received: 18 June 2012/Accepted: 18 February 2014

ABSTRACT

Infiltration caused by rainfall will lead to the changes of moisture content and soil pore water pressure or matric suction of the soil. These changes indicate the behavior of the soil especially during wetting and drying process. This paper presents the experimental test result of rain water infiltration into soil column for two samples of soils. The main objectives were to study the effect of rainfall intensity and duration of soil infiltration process for the forest soil and to compare its result to the gravelly sand. Infiltration experimental in this study involved three main components; water supply system, soil column and instrumentations, including percolation collection system. This study uses two types of tensiometers; 5 and 10 cm long. The results of TDR and tensiometers which were used to obtained moisture content and matric suction, respectively, shows that the system was successfully developed. For the forest soil, the result showed that moisture content of the top section is higher compared with the other sections. On the other hand, for gravelly sand, the moisture content in middle section is higher compared with the top and bottom section of the soil. Meanwhile, matric suction for both soils dropped during rainfall and gradually increases towards drying process. Other than that the comparison of soil matric suction between 5 and 10 cm tensiometers shows significant results for gravelly sand compared to forest soil.

Keywords: Infiltration; matric suction; soil column; soil moisture

ABSTRAK

Penyusupan yang disebabkan oleh hujan akan merubah kandungan lembapan dan tekanan air liang tanah. Perubahan ini adalah merupakan penanda kepada sifat tanah terutamanya semasa proses pembasahan dan pengeringan daripada hujan yang turun. Kertas kerja ini memaparkan keputusan yang dicapai daripada uji kaji makmal berdasarkan ujian air hujan yang menyusup ke dalam dua sampel tanah. Objektif utama kajian ini adalah untuk mengkaji kesan daripada keamatan dan tempoh air hujan untuk sampel tanah dari kampus dan dibandingkan dengan sampel pasir berkerikil. Ujian penyusupan ini terbahagi kepada tiga komponen; sistem bekalan air, tiang tanah dan instrumentasi dan juga sistem pengaliran keluar air. Kajian ini menggunakan dua jenis tensiometer; 5 dan 10 cm panjang. Keputusan yang diperoleh menunjukkan tanah dari kampus mempunyai kandungan lembapan yang tinggi pada bahagian atas tiang dibandingkan dengan bahagian yang lain. Manakala pasir berkerikil pula, tanah pada bahagian tengah tiang menunjukkan kandungan lembapan yang tertinggi. Selain daripada itu, tekanan air liang tanah untuk kedua jenis tanah ini menunjukkan pengurangan semasa hujan, tetapi beransur meningkat semasa proses pengeringan. Selain daripada itu, didapati tekanan air liang antara 5 dan 10 cm tensiometer menunjukkan kesan pada pasir berkerikil berbanding dengan tanah dari kampus.

Kata kunci: Kandungan lembapan; penyusupan; tekanan liang; tiang tanah

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*Corresponding author; email: mmukhlis@vlsi.eng.ukm.edu.my