William M. Shehata

Assessment of the industrial utilization of scoria materials in central Harrat Rahat, Saudi Arabia

Although basaltic volcanic scoria deposits are widespread in and around the scoria cones present in the Harrats, very few occurrences have been evaluated and still fewer have been exploited. The scoria from a quarry in central Harrat Rahat was investigated and assessed for its industrial utilization. Cubes were prepared from several concrete mixes using scoria as lightweight coarse and fine aggregates in different percentages. The compressive strength values of the cubes were found to be acceptable and satisfy the ASTM (1995) requirement for structural concrete. The scoria was also assessed for its utilization as a cement additive. Pozzolanic activity was tested according to the Italian standards and found to be acceptable. The strength activity index with Portland cement and the effectiveness of scoria admixture in controlling alkali-silica reactions were tested according to ASTM (1995) standards. Mortar cubes were specially prepared for these studies using different mixes and different storage procedures. The results satisfied the ASTM (1995) requirements as cement additive. The utilization of scoria as a heat-insulating material was tested and the results were found to satisfy the ASTM (1995) requirements. This fact suggests it could be utilized in the manufacture of the building blocks. It is recommended to evaluate the other scoria deposits, exploit the economically feasible ones and utilize them for different industrial applications. The manufacturing of heat-insulating concrete or building blocks using scoria is of prime importance as an energy saver.

Preconstruction solution for Groundwater rise in Sabkha

Sabkha deposits are formed under arid conditions and are considered as a common problematic soil along the coastal area of the Arabian Gulf. Saudi Arabia. One of the most serious problems associated with the coustruction on sabkha is the rise of groundwater level causing settlement and hence imposing additional stress on the structural elements. Groundwater rise in sabkha was attributed to numerous reasons; the interruption of the natural evaporation by construction is considered to the most prominent. The evaporation data along the Arabian Gulf coast had been analyzed and the possible rise in the groundwater level had been predicted using both the evaporation and soil porosity data. A horizontal drain is suggested to interrupt the capillarity in the soil and to drain the infiltrating water and hence stop the groundwater rise. A mathematical model for the optimum selection of the drain characteristics is presented. This model requires the knowledge of some site conditions such as the area to be drained, the thickness of the aquifer and the soil coefficient of permeability. Based on these values a design curve can be constructed to relate the horizontal drain characteristics such as the longitudinal transmissivity of the drain, its thickness and its slope. An example using the parameters of a specific site conditions along the Arabian Gulf coast is given to present the suggested design curve. The relative significance of these parameters on the drain characteristics and geometry is also discussed.RésuméLes dépôts de sabkha se font dans des conditions arides et sont considérés comme des sols posant des problèmes tout au long de la côte du Golfe arabo-persique en Arabie Saoudite. L’un des problèmes les plus sérieux associés à la construction sur des sabkha est la remontée du niveau de la nappe qui provoque des affaissements et en conséquence entraîne des contraintes supplémentaires pour les structures. La remontée de l’eau dans les sabkha a été attribuée à de nombreuses causes: l’interruption de l’évaporation naturelle due aux constructions est considérée comme l’une des principales. Les données concernant l’évaporation le long de la côte du golfe arabo-persique ont été analysées et la remontée probable du niveau de la nappe a été estimée, en utilisant à la fois les données sur l’évaporation et sur la porosité des sols. Les auteurs suggèrent la mise en place de drains horizontaux pour interrompre les remontées capillaires dans les sols et pour draîner les eaux d’infiltration. L’article présente un modèle mathématique permettant un choix optimal des caractéristiques des drains. Ce modèle suppose la connaissance des conditions du site, telles que la surface à draîner, l’épaisseur de l’aquifère et le coefficient de perméabilité des sols. En s’appuyant sur ces valeurs, on peut calculer les éléments de conception des drains, tels que leur transmissivité longitudinale, leur épaisseur et leur pente. L’exemple d’un site particulier le long du golfe arabo-persique est pris pour présenter des éléments de calcul suggérés. La signification relative de ces paramètres sur les caractéristiques des drains est également discutée.