Weak rocks are available in different areas in Sudan. These include sandstone, mudstone, siltstone usually referred to as Nubian Formations (N.F.). Clastic limestones are present in other areas of Sudan. Organic limestones in the form of coralline deposits are present in eastern Sudan, mainly on the Red Sea coast. Weak rocks constitute an important geological feature on which the foundations of most of the important structures are resting. The sandstone is also used as a primary buildingmaterial or as a facing stone over other construction. The geotechnical properties of these formations were investigated bydifferent insitu and laboratory testing methods. This paper summarizes the origin, distribution of Nubian formation and limestone. The paper also presents most of available data on the geotechnical properties of these formations. It is concluded that the Nubian formation and limestone coral deposit are weak rocks with poor quality of core samples; hence feld testingmay give better geocharacterization result for such deposit.

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Cavitation damage process of stainless steel during the incubation period was detected and evaluated using stepwise erosion technique and image processing. The damage experiments were conducted using the vibratory test rig. The scanning electron microscope images at different locations on eroded surface using stepwise technique were presented. In addition, the surface roughness was measured with the testing time. Discrete wavelet transforms and fractals had been adopted to extract the relevant features. It was found that the feature parameters: Shannon entropy, energy loss, fractal dimension and intercept show a fairly linear increase with the testing time. It was also observed that the feature parameters have reasonable correlations with the roughness parameters.

In this paper methods for determination of maximum local scour depth and eroded material volume downstream of highway drainage structures were developed. Severe local scour leads to undermining followed by collapsing of the drainage structure. The analysis method is based on integrating a new technique of improved drainage structure outlet geometry, jet hydraulic characteristics and soil properties. The jet velocity, induced shear stress, critical shear resistance to erosion and particle size are the main factors that control the erosion process downstream of a drainage structure. The study is of experimental and theoretical nature. The developed mathematical model was calibrated using collected field data in addition to laboratory tests. The produced scour holes were plotted for each laboratory run and the scour hole depth, width and length were measured. A semi- empirical relation has been developed for predicting the depth of local scour hole. It is based on Densimetric Froude number. It is found that the semicircular apron gives less scour depth and width when compared to the linear front apron. The comparison of the model outputs and field study is found of a good agreement. The model is recommended for engineering design of highway drainage structures located on streams of sandy bed.