Kamarudin Ahmad

Observation of Light Non-Aqueous Phase Liquid Migration in Aggregated Soil Using Image Analysis

Physical model experiments were conducted to observe the migration of light non-aqueous phase liquids (LNAPL) in a double-porosity soil medium. The double-porosity characteristics of the soil were simulated through aggregation of kaolin which resulted in well-defined intra-aggregate and inter-aggregate pores. Digital images were collected to monitor LNAPL (modeled by toluene) migration. A special experimental setup was developed to enable the instantaneous capture of the LNAPL migration around the whole soil column using a single digital camera. An image processing module was applied to the captured images and the results plotted using a surface mapping programme. Events observed during the duration of the experiments were discussed. It was found that the LNAPL flowed much faster in the aggregated soil as compared to a single-porosity soil. The wettability of the fluid and the capillary pressure characteristics were demonstrated to be influential factors in immiscible fluids migration when the soil fabric showed highly contrasting porosity values.

Sustainable Design of Compacted Laterite Soil Liner

Laterite soil, as one of the major groups of tropical residual soils, was investigated in application for engineered sanitary landfill liner. The laterite soil was used as a stand-alone material without any additives and subjected to different gradation to check its geotechnical potentiality as a sustainable material for liner. Specimens were prepared at different moulding water contents, i.e. optimum moisture content (OMC), dry of OMC and wet of OMC. Tests were carried out on natural soil 30, 40 and 50% fine content by dry weight of soil sample. The results showed that laterite soils should contain at least a minimum of 50% fine gradation to be used as liner. The outcome of this research is expected to serve as a sustainable guide to geotechnical/geo-environmental engineers in using laterite soil as a material in the construction of hydraulic barriers used for engineered sanitary landfill system in tropical countries of the world.

Utjecaj temperature na stišljivost i potencijal kolapsibilnosti rezidualnog granitnog tla

U ovom se radu istražuje utjecaj temperaturnih promjena na indeks stišljivosti i potencijal kolapsibilnosti rezidualnog granitnog tla na koje se često nailazi u Maleziji. Zbijeno tlo analizirano je pomoću modificiranog edometra s kontrolom temperature. Dvije serije uzoraka tla s raznim vrijednostima suhe gustoće ispitane su pri temperaturama od 27, 40 i 60°C. Rezultati ispitivanja pokazuju da vrijednost indeksa stišljivosti ne ovisi o temperaturi. S druge strane, grijanje dovodi do smanjenja potencijala kolapsibilnosti, a ta je pojava izraženija pri niskim vrijednostima suhe gustoće.

Vegetative induced ground displacements: A comparison of numerical and experimental study

A volume change was modeled as a result of matric suction change caused by vegetative induced moisture transfer. Theory of unsaturated soil mechanics and two stress state variables principles approach was used in the stress-deformation model. The negative pore-water pressures are estimated through governing partial differential equations for unsaturated soils. The results of the root wateruptake analysis are then used as an input for the prediction of ground displacements in a stressdeformation analysis in an uncoupled manner. A mature Leyland Cypress tree located on Gault clay was analyzed, covering a full spring/summer drying period for the first case study. The second and third cases were analysis on Mature Lime tree located on a Boulder clay sub-soil for period covering a full spring/summer drying period; while the third case considered field capacity in winter and extends through a full spring/summer drying period and subsequent autumn recharge. Time varying boundary conditions have also been considered in the third case and the sink term was activated to represent water uptake by transpiration, during spring/summer soil-drying phase and deactivated during the autumn/winter recharge phase. The stress-deformation model has been validated by direct comparison to field measurements recorded for three cases. A good overall correlation between field data and simulated results has been achieved where the difference between the two set of results was less than 5% for all cases considered.