Tujuan kajian ini adalah untuk mengkaji tindak balas hidrologi cerun tanah residu granit tak tepu berdasarkan kepada kesan keamatan hujan dan sudut cerun yang berbeza. Kajian ini melibatkan ciri-ciri tanah residu granit dan eksperimen model cerun fizikal 2D. Pencirian tanah dijalankan ke atas pasir sungai (SW) dan tanah residu granit (SC) yang diperolehi dari Kampus USM Utama, Pulau Pinang menggunakan kaedah ujian tanah di lapangan dan makmal. Eksperimen model cerun fizikal 2D dijalankan bersama sistem simulator hujan, Time Domain Reflectometry (TDR) dan sistem tensiometer-transduser untuk menganalisis kepentingan sifat tanah dari segi tindak balas hidrologi seperti sedutan matrik tanah dan kandungan kelembapan tanah. Jumlah penyerapan air hujan dan air larian di permukaan juga diukur di penghujung eksperimen. Jumlah hujan yang diserap ke dalam tanah dan yang menjadi air larian di permukaan dengan intensiti hujan dan sudut cerun yang berbeza boleh dianggarkan. Dengan menjalankan model cerun fizikal 2D, didapati bahawa peratusan penyerapan air hujan dan kandungan kelembapan tanah mempunyai perbezaan yang sedikit tetapi perbezaan yang besar di antara pasir sungai (SW) dan tanah residu granit (SC) dari segi air larian di permukaan apabila kecerunan tanah meningkat. Dua nilai kadar hujan yang berbeza digunakan dalam kajian ini adalah berdasarkan kepada data dari intensiti hujan yang direkodkan oleh stesen hujan di Air Itam, Pulau Pinang. Data hujan ditukar dengan menggunakan persamaan kadar aliran, Q (butiran terperinci boleh dirujuk di bahagian 3.4.7.1). Ketika keamatan hujan 9.78×10-9m/s dan 1.66×10-9m/s, nilai minimum air larian di permukaan untuk pasir sungai (SW) direkodkan ialah 15.7% dan 9.2% manakala nilai maksimum masing-masing adalah 28.9% dan 25.9%. Bagi tanah baki granit (SC), nilai minimum air larian di permukaan dicatatkan adalah 30% dan 30.19% manakala nilai maksimum adalah 54% dan 50.06% masing-masing untuk kadar curahan hujan gunaan bagi 9.78×10-9m/s dan 1.66×10-9m/s. Berdasarkan keputusan untuk kedua-dua pasir sungai (SW) dan tanah baki granit (SC), persamaan berkaitan dengan penyerapan air, air larian di permukaan dan kandungan kelembapan tanah dibentuk. Bagi pasir sungai (SW), persamaan penyerapan air hujan, air larian di permukaan dan kandungan kelembapan tanah adalah y=43.78x-0.408, y=16.47x0.4389 dan y=37.737x-0.712 semasa kadar curahan hujan gunaan ialah 9.78×10-9m/s manakala pada 1.66×10-9m/s persamaan tersebut direkodkan adalah seperti y=45.218x-0.316, y=9.9649x0.7318 dan y=23.091x-0.382. Bagi tanah baki granit (SC), semasa kadar curahan hujan gunaan 9.78×10-9m/s persamaan bagi penyerapan air hujan, air larian di permukaan dan kandungan kelembapan tanah adalah y=42.582x-0.493, y=28.254x0.4409 dan y=34.945x-0.314 manakala y=40.633x-0.386, y=29.754x0.3589 dan y=35.62x-0.384 semasa 1.66×10-9m/s kadar curahan hujan gunaan. Dengan mengambil kira jumlah hujan yang menyerap masuk ke dalam tanah dan menjadi air larian di permukaan, kedua-duanya didapati mengalami penurunan dalam penyerapan air hujan dan kandungan kelembapan tanah tetapi meningkat bagi air larian di permukaan apabila kecerunan sudut tanah meningkat. Ini membuktikan bahawa, peningkatan kecerunan sudut tanah juga meningkatkan kandungan air hujan yang menjadi air larian di permukaan daripada diserap ke dalam tanah.
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The aim of this study is to investigate the effect of different applied rainfall rate and slope angle on the hydrological response of unsaturated soil slope. This study involved the granitic residual soil characterization and 2D physical slope model experiments. Soil characterizations included in this study are in-situ and laboratory soil tests which was conducted on the river sand (SW) and granitic residual soil (SC) obtained from the USM Main Campus, Penang Island. The 2D physical slope model experiment is conducted with the rainfall simulator system, Time Domain Reflectometry (TDR) and tensiometer-transducer system to analyze the significance of soil properties in terms of hydrological responses which are soil suction and water content. The amount of rainfall infiltration and surface runoff were also measured by the end of the experiment. The amount of rainfall infiltrated into the soil and became surface runoff with difference applied rainfall rate and slope angles can be estimated. By conducted 2D physical slope model, it was found that the percentage for water infiltration and soil moisture content were slightly different, but substantially different in surface runoff when the soil slope angle increased between river sand (SW) and granitic residual soil (SC). Two difference value of applied rainfall rate used in this study is based on the data from rainfall intensity recorded by the rainfall station in Air Itam, Penang. The rainfall data are converted by using the flow rate, Q equation (details can be referred in section 3.4.7.1). During the applied rainfall rate of 9.78×10-9m/s and 1.66×10-9m/s, the minimum surface runoff for river sand (SW) recorded are 15.7% and 9.2% whereas the maximum surface runoff are 28.9% and 25.9% respectively. As for granitic residual soil (SC), the minimum surface runoff recorded are 30% and 30.19%, while the maximum surface runoff are 54% and 50.06% of applied rainfall rate of 9.78×10-9m/s and 1.66×10-9m/s respectively. Based on the results of both river sand (SW) and granitic residual soil (SC), the equations related to water infiltration, surface runoff and soil water content are obtained. For river sand (SW), the equations of water infiltration, surface runoff and soil moisture content are recorded as y = 43.78x-0.408, y = 16.47x0.4389 and y = 37.737x-0.712 during the applied rainfall rate of 9.78×10-9m/s while during 1.66×10-9m/s the equations are recorded as y = 45.218x-0.316, y = 9.9649x0.7318 and y = 23.091x-0.382. For granitic residual soil (SC), the equations of water infiltration, surface runoff and soil moisture content during applied rainfall rate of 9.78×10-9m/s are recorded as y = 42.582x-0.493, y = 28.254x0.4409 and y = 34.945x-0.314 while y = 40.633x-0.386, y = 29.754x0.3589 and y = 35.62x-0.384 during 1.66×10-9m/s applied rainfall rate. By measured the amount of the rainfall seeped into the soil and became surface runoff, it was found that both soils decrease water infiltration and soil moisture content but increase surface runoff when slope angle increased. These proved that, as the slope angle increased more rainfall became surface runoff than infiltrated into the soil.
Hydrological response of unsaturated granitic residual soil slope due to different rainfall amounts and slope angle_Nur Hasliza Hamzah_A9_2017_MYMY