Kegagalan cerun berpunca daripada hujan merupakan salah satu isu geoteknik yang biasa di kawasan tropika. Penyelidikan dalam bidang kestabilan cerun telah membawa kesedaran bahawa kebanyakan kegagalan cerun disebabkan oleh penyusupan air hujan ke dalam cerun. Infiltrasi air hujan ke dalam cerun tanah berkemungkinan akan menjejaskan kestabilan cerun dengan mengubah tekanan air liang dalam tanah yang mengawal kandungan air dalam tanah. Salah satu cerun di Pulau Pinang telah dipilih untuk mengkaji ciri-ciri penyusupan di cerun tanah. Asas kajian ini adalah untuk menjalankan penyelidikan pada beberapa aspek teori tanah dengan menjalankan penyiasatan tapak, bidang instrumentasi, ujian makmal dan permodelan berangka. Semua data yang dikumpulkan untuk menyimpulkan pengaruh penyusupan hujan pada sifat-sifat kejuruteraan tanah cerun semasa hujan. Bidang instrumentasi dan ujian akan dijalankan bagi menentukan parameter tanah: insitu ketumpatan, kadar penyusupan dan kekonduksian hidraulik daripada tanah. Ujian makmal akan dilakukan untuk menentukan sedutan matrik tanah, kandungan air tanah, jenis tanah dan graviti tentu tanah. Berdasarkan ujian yang telah dilaksanakan, nisbah lowong dan keliangan tanah didapati berkurangan dengan kedalaman tanah. Ketumpatan pukal dan ketumpatan kering tanah pula meningkat dengan kedalaman tanah kerana lebih rendah keliangan tanah pada kedalaman yang lebih besar. Sebaliknya, kadar infiltrasi tanah dan sedutan matrik tanah berkurangan dengan peningkatan kandungan air tanah. Permodelan berangka telah dilakukan untuk mengesahkan dan meramalkan hubungan antara tindak balas penyusupan-sedutan dan darjah ketepuan. Permodelan berangka boleh digunakan untuk mengintegrasikan senario hujan ke dalam tafsiran isu tanah runtuh. Oleh itu, rancangan pembangunan dan langkah-langkah pencegahan boleh direka untuk anggaran kesan daripada penilaian berdasarkan data yang dikumpul.
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Rainfall-induced slope failure make up one of the most common geotechnical hazards in tropical regions. Studies and research in the area of slope stability have brought about the realization that most failures of slope are caused by the infiltration of rainwater into a slope. Infiltration of rainwater into a residual soil slope may impair slope stability by altering the pore-water pressure in the soil which controls the water content of the soil. To study the infiltration characteristics in slopes, an unsaturated residual soil slope in Penang was instrumented. The basics of this study were to perform full scale research on several aspect of unsaturated soil theory by performing site investigation, field instrumentation, laboratory testing, laboratory experiment and numerical modeling. Field instrumentation and testing were carried out to determine the soil parameters: insitu density, infiltration rate, and hydraulic conductivity of soils. Laboratory testing and laboratory experiment were done to determine the soil suction, soil water content, type of soil and specific gravity of soil. All the data were compiled to conclude the influence of rainfall infiltration on soil engineering properties of slope during rainfall. Based on the testing performed, void ratio and porosity of soil are found to be decreasing with depth while the bulk density and dry density of soil are increasing with depth due to lower porosity of soil at greater depth. On the other hand, soil infiltration rate and matric suction of all depths decrease with the increase of volumetric water content as well as the degree of saturation. Numerical modeling was done to verify and predict the relationship between infiltration-suction response and degree of saturation. Numerical models can be used to integrate the rainfall scenarios into quantitative landslide hazard assessments. Thus, development plans and mitigation measures can be designed for estimated impacts from hazard assessments based on collected data.
Analysis of infiltration-suction response in unsaturated residual soil slope / Chong Kim Wee