Pencemaran tanah oleh minyak diesel kebiasaannya berlaku disebabkan tumpahan minyak daripada kenderaan, kemalangan kebocoran daripada tangki atau kebocoran paip air. Pencemaran ini menyebabkan kerosakan yang ketara terhadap alam sekitar. Hidrokarbon yang terdapat dalam minyak berterusan memberi kesan kepada kualiti dan ciri fizikal tanah. Berikutan dengan keadaan ini, tujuan penyelidikan ini ialah seharusnya untuk belajar tentang kesan dengan memperkenalkan jumlah Ringan Bukan Berair Fasa Cecair (RBRFC) ke dalam struktur pasir gred tidak baik dengan mempertimbangkan perubahan aras air. Kelakuan RBRFC bergerak diperhatikan dan diterangkan. Satu ujian lajur dimensi dan kaedah analisis gambar telah digunakan. Kes yang pertama melibatkan aras air yang mulanya turun dan kemudiannya naik. Dalam kes ini, minyak diesel terperangkap dalam kawasan tepu adalah sebanyak 9 % apabila 50 ml minyak diesel digunakan dan 4 % apabila 25 ml minyak diesel digunakan. Kes yang kedua melibatkan aras air yang mulanya naik dan kemudiannya turun. Dalam kes ini, jumlah minyak diesel terperangkap dalam kawasan tidak tepu ialah 10% apabila 50 ml minyak diesel digunakan dan 3 % apabila 25 ml minyak diesel digunakan. Di antara keadaan dan kemungkinan yang diberikan, yang paling kritikal ialah apabila aras air turun dan kemudiannya naik, dengan jumlah minyak diesel sebanyak 50 ml.
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Soil contamination by diesel oil normally occurs due to spillage from vehicles, accidental discharge from tanker, or leaks in pipes. This type of contamination causes significant destruction to the environment. The hydrocarbon of the diesel oil continuously impacts the quality and physical characteristics of soil. In regard to these concerns, the main aim of this research has been to study the effects of introducing a volume of the Light Non Aqueous Phase Liquid (LNAPL) into a body of poorly graded sand with the water table fluctuated. The behaviour of LNAPL migration was observed and described. The one dimensional column test and Simplified Image Analysis Method (SIAM) were employed. The first case involved a water table that was first lowered and then raised. In this case, the amounts of diesel oil that was entrapped in the saturated soil were 9 % when 50 ml of diesel oil was used and 4 % when 25 ml of diesel oil was used. The second case involved a water table that was first raised and then lowered. In this case, the amounts of diesel oil that was entrapped in the unsaturated soil were 10 % when 50 ml of the diesel oil was used and 3 % when 25 ml of diesel oil was used. Among the given circumstances and possibilities, the most critical was when the water table was lowered and then raised, with 50 ml of diesel oil used.