Abdel-Mohsen O. Mohamed

Development of a criterion for road surface roughness based on power spectral density function

Abstract This study has demonstrated that the non-contact acoustical transducer is a reasonable sensor for reflecting the road roughness profile, and the procedure is much faster in detecting the road surface roughness as compared to other measurement devices. Thus, it is a very promising sensor with regard to road roughness measurement. Furthermore, the ISO may be employed to classify the road grade. However, the assumed linearity in the PSD on a log-log graphical representation may not be true in reality, especially in the lower frequency band. Therefore, a new approach to classify road surface roughness is to be developed.

Hydro-thermal performance of unsaturated bentonite-sand buffer material

Abstract Several series of one-dimensional heat and moisture flow tests were performed to examine the moisture and temperature distributions in the buffer material compacted to a dry density of 1.67 Mg m −3 and water content of 17.7%. In all tests, water was allowed to infiltrate into a horizontal soil column from one end under a constant hydrostatic head of 276 kPa. Also the specimens were heated from the other end by the heater to a constant temperature. It is experimentally demonstrated that the moisture moves from both ends toward the mid part of the soil column due to both thermal gradient from one end and hydraulic gradient from the other end. It was observed that, in spite of no overall volume change, local volume change occurs in the system. The measured temperatures along the length of the specimen indicate that temperature distributions stabilize within a short period of time. The time required for the temperature to stabilize decreases as the heater skin temperature increases. The diffusivity parameters are calculated using the measured moisture and temperature profiles combined with the finite difference method. Powells optimization algorithm was used to determine the material parameters. Good agreements between experimentally measured and calibrated volumetric water content shows that the diffusion parameters can be expressed in a linear function of the volumetric water content and temperature.

Evaluation of coupled heat and moisture flow parameters in a bentonite-sand buffer material

Several series of one-dimensional tests were used to study the nature of transient heat and moisture movements in a clay buffer under different imposed temperature gradients. The measured temperature and moisture profiles were used to calculate the diffusion parameters governing heat and moisture movement in the buffer material. The experimentally determined diffusion parameters are shown to be dependent on the moisture content and temperature. The diffusion parameters were calculated by using an identification technique, the root-time method, and an analytical technique.

Coupled heat-mass transport effects on moisture redistribution prediction in clay barriers

Abstract The issues associated with coupled transient heat and mass transfer in unsaturated clay barriers surrounding a buried heat source are considered, and the effects of driving forces in both the liquid and vapour phases are discussed. The reasons for the inability of the model of Philip and de Vries (1957) to accurately predict the redistribution of moisture in unsaturated clay barriers are explained. The model of Yong and Xu (1988) is used to predict the moisture redistribution of non-swelling unsaturated clay barriers. The large variations of the moisture values predicted by the two models are also discussed.

Flooding of a mine tailing site: Suspension of solids - Impact and prevention

ABSTRACT Acid generating tailings is a problem to be solved in the mining industry. By limiting the available oxygen for the oxidation process, water covers is one of the methods to control the acid generation. This study evaluates the optimum height of water required to prevent the resuspension of solid particles and thus reducing the environmental impact on a specific site (Solbec Cupra). Based on the experimental results, it has been found that the minimum height of water above the reactive tailing should be 1.34 m. However, with a layer of sand on top of the tailings, the required level may be reduced to 0.74 m. Also, it has been calculated that a layer of sand can reduce the total sediment load from 331.10 to 41.80 m3/m/day.

Experimental study on yielding and failure of an anisotropic clay

Abstract The effect of initial and stress-induced anisotropies on yielding and failure of an anisotropic clay has been studied experimentally by loading soil samples along different stress paths under triaxial stress. Five orientations of bedding planes of clay fabric were tested. In all the loading paths, it was observed that the strain increment vectors were not coaxial with the stress vectors. The degree of disassociation depended on initial fabric anisotropy and stress-induced anisotropy. The test results indicated that for the inherently anisotropic material, there is no particular requirement (a) for the yield and plastic potential surfaces to coincide, and (b) for an associated flow rule to hold.

Modeling of Tyre-Clay Soil Interaction via Quasi-Static Moving Boundary Displacement Method

A vehicle mobility model has been developed using energy principles and a quasi-static moving boundary displacement method. For a given condition of both tyre and terrain characteristics, the model calculates the contact length, the slip rate, the traction efficiency and the drawbar pull. The effect of tread configuration is also included in calculating the slip rate. A numerical example is given to demonstrate the capability of the new developed mode. The models predictions are also compared with the experimental results in the laboratory tests and a good agreement is obtained.