Seismic Microzonation of Central Khartoum, Sudan

A preliminary seismic microzonation of Central Khartoum, Sudan is proposed. Khartoum, the capital of Sudan, is located at the confluence of White and Blue Niles. The city is heavily populated. The Central Khartoum with its high rise buildings is the center of governmental and business activities and is located on strip adjacent to the Blue Nile. Geological and geotechnical data indicated that the subsoil conditions at Central Khartoum are characterized by alluvial deposits underlain by Nubian Sandstone below a depth of 20 m. The alluvial deposits locally known as Gezira formations, consist of clays grading into silt and sand with depth. Macro seismic zonation of Sudan and its vicinities, developed by the authors, gave the ground acceleration at the bed rock surface. The effect of alluvial deposits at Central Khartoum on propagation of seismic motion parameters to the ground surface is investigated in this study. Correlations are proposed for pertinent cyclic soil properties such as shear modulus, damping, and shear wave velocity. The classical shear beam model developed by Idriss and Seed is used to study the effect of local soil conditions on ground motion parameters. In absence of strong motion records, artificial time histories of ground motion parameters are used. Plots showing the time histories of ground motion parameters at the ground surface are obtained. The results indicated amplification of ground acceleration of up to 1.15. Because of the presence of saturated loose to medium dense sand at some locations within Central Khartoum, the risk of earthquake-induced liquefaction is evaluated. The susceplity of subsoils in Central Khartoum to liguefaction is evaluated probabilistically by modifying the classical method developed by Seed and Idriss. The risk of earthquake-induced liquefaction is computed by combining the seismic hazard and the conditional probability of liquefaction. The study showed that the risk of liquefaction is low

Effects of Gradation, Moisture and Density on Strength, Stiffness and Deformation Resistance of Pure Crushed Stone Base Blend

This paper investigates the effect of some physical properties on strength, stiffness, and deformation resistance of pure dense well graded crushed stone base blends. Manufactured crushed basaltic stone of three different particle sizes from Jebel Touryia was adopted for this study. Initially, attempt was performed to produce number of base blends from mixing these crushed particle sizes. Only two base blends are found to satisfy TRL GB3 base gradation requirements

DESIGN PRACTICE OF BORED PILES IN NUBIAN FORMATION CASE STUDY: FOUNDATION AND BRIDGES IN KHARTOUM

The term Nubian Sandstone Formation or Nubian Formation (NF) is applied in the Sudan to those bedded and usually flat-lying conglomerates, grits, sandstones, sandy mudstones and mudstones that rest unconformably on the Basement Complex and the Paleozoic sandstones. These formations are either exposed or covered by the recent quaternary formations. They cover large areas in Northern, Central Western and Eastern Sudan. Several important heavy structures such as bridges across the rivers and high rise buildings in Khartoum are supported on these formations. The factors controlling their performance as foundation materials are the type and amount of cementing material for the sandstones; the heterogeneity, degree of weathering and the type and consistency of the mudstones and the characteristics of the formations covering them. Different approaches were used for the design of piles resting or penetrating NF. This paper summarizes the geotechnical characteristics of five bridge sites in Khartoum and the approaches used by the designers for estimating the bearing capacity of the piles supporting these bridges. The piles were all socketed into the NF. The designs were compared with the results from pile load tests carried out in the bridge sites. The analysis has shown that the approaches used for estimating the pile capacities in the NF are very conservative and un-realistic. Alternative design approaches or improvements of the currently used designs are neede

Barriers of exclusive breastfeeding among mothers attending primary health-care centers in Jazan, Saudi Arabia

Background: Exclusive breastfeeding (EBF) describes infants who were only breastfed for 6 months. Many Saudi mothers have suboptimal breastfeeding practices. Therefore, this study aims to assess breastfeeding knowledge and determine barriers to EBF among mothers attending primary health care centers in Jazan City. Methods: A descriptive cross-sectional study was done that included all mothers attending the PHC centers. Data were collected through a self-administered questionnaire. Results: Most study participants understand breastfeeding's health benefits for babies and mothers, but most believe that synthetic milk is the best alternative for working mothers to feed their babies. A percentage of 66.7 of mothers practiced breastfeeding during the first 6 months of the child's life. EBF shows a significant relationship with knowledge and barriers. Sixty percent of mothers have never had any information about breastfeeding; the primary source was from their mothers and only 31.4% from hospital staff. Most respondents disagreed with statements of barriers to EBF, which elicits an unexpected response. Conclusions: Most participants have good knowledge concerning breastfeeding benefits for both mother and infant and disagreed on the mentioned barriers for EBF that include lack of breastmilk, deficiency of information, and working conditions