Browsing by Author "Habib-ur-Rehman Ahmed"

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Characterization and stabilization of Eastern Saudi Marls
(Saudi Digital Library) Habib-ur-Rehman Ahmed
Calcareous soils, locally known as marls, are extensively exploited in the construction of highways and building foundations. Despite their wide prevalence all-over the world, a review of the literature indicates that calcareous soils have received little attention from the geotechnical community. Therefore, this comprehensive research program was devoted to study first the characterization and the geotechnical properties of eastern Saudi calcareous soils. Marl sample were collected from over 20 different sites in the Eastern Province od Saudi Arabia. The samples were characterized and their geotechnical properties were determined. Based on these tests, it was found that marl soils are extremely sensitive to the molding and testing moisture contents. The existing classification systems and specifications are of limited applicability to these soils classification systems and specifications are of limited applicability to these soils. Owing to their poor engineering behavior, the second phase of this research program focused on improvement and stabilization of some selected marl soils. The selection was based not only on the poor behavior of these soils, but also the availability of these soils and their potential future use. Mechanical and chemical soils stabilization techniques were investigated. Chemical stabilization using cement was found to be an effective and efficient way to significantly improve the inferior properties of these soils in terms of strength and durability. This research has opened a new door towards a better and more economical utilization of the low quality marl soils in eastern Saudi Arabia in particular, and calcareous soils worldwide in general.
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Molecular level modeling of natural and compacted expansive clays
(Saudi Digital Library) Habib-ur-Rehman Ahmed
ﺗﻌﺗﺑر اﻟﺗرﺑﺔ اﻟطﯾﻧﯾﺔ اﻟﻘﺎﺑﻠﺔ ﻟﻼﻧﺗﻔﺎخ واﻟﺳﺎﺋدة ﻋﻠﻰ ﻧطﺎق واﺳﻊ ﻛﺄﺣد اﻟﻣواﺿﯾﻊ اﻻﻛﺛر ﺗﺣدﯾﺎ ﻓﻲ اﻟﺟﯾوﺗﻘﻧﯾﺔ، اﻟﺟﯾوﺑﯾﺋﯾﺔ ، ھﻧدﺳﺔ اﻟﺑﺗرول، واﻟزراﻋﺔ، واﻟﻣﺟﺎﻻت اﻟدواﺋﯾﺔ. ھذه اﻟطﯾن او اﻟﺗرﺑﺔ ﺗﺗﻌرض ﻟﺗﻐﯾر ﻓﻲ اﻟﺣﺟم ﻧﺗﯾﺟﺔ ﺗﻐﯾﯾر ﻓﻲ اﻟرطوﺑﺔ، ﻣﻣﺎ ﯾؤدي اﻟﻰ ﻣﺷﺎﻛل اﺳﺗﻘرار اﻟﮭﯾﺎﻛل اﻟﺗﻲ ﺗﺄﺳﺳت ﻋﻠﻰ ﻣﺛل ھذه اﻟطﺑﻘﺎت. ھذا اﻟطﯾن اﻟﻘﺎﺑل ﻟﻼﻧﺗﻔﺎخ ﯾﺗوﺟد ﺑﺷﻛل ﻛﺑﯾر ﻓﻲ اﻟﻣﻣﻠﻛﺔ اﻟﻌرﺑﯾﺔ اﻟﺳﻌودﯾﺔ وﯾﺗرﻛز ﻣﻌظﻣﮭﺎ ﻓﻲ اﻟﻣدن اﻟﺳﻛﻧﯾﺔ. وﺗﺗﻌﺗﺑر اﻟﺣﻠول واﻟﺻﯾﻎ اﻟﺗﺟرﯾﺑﯾﺔ واﻻﺧﺗﺑﺎرﯾﺔ اﻟﻘﺎﺋﻣﺔ واﻟﻣﺳﺗﺧدﻣﺔ ﻟﻠﺗﻧﺑؤ ﺑﺎﺣﺗﻣﺎﻟﯾﺔ اﻻﻧﺗﻔﺎخ ﻟﮭذا اﻟﻧوع ﻣن اﻟطﯾن او اﻟﺗرﺑﺔ ﻏﯾر ﻗﺎدرة ﻋﻠﻰ ﺗوﻓﯾر اﻟﻔﮭم اﻟﺷﺎﻣل ﻟﻠﺗﻐﯾرات اﻟﻣﺣﺗﻣﻠﺔ ﻓﻲ ﻧﺳﯾﺞ وھﯾﻛل اﻟﺗرﺑﺔ اﻟطﺑﯾﻌﻲ واﻟﻣدﻣوك. ﺗﻠﻌب ﻋﻣﻠﯾﺎت اﻟﻧﺎﻧو أو اﻟﺟزﯾﺋﺎت دورا ﻣﺣورﯾﺎ ﻓﻲ ﺗﻐﯾﯾر اﻟﺳﻠوك اﻟﺣﺟﻣﻲ ﻟﻠطﯾن اﻟﻣﻧﺗﻔﺦ، واﻟذي ﯾﻛون ﻓﻘط ﻓﻲ اﻟﺳﻠوك اﻟﺣﺎﻟﻲ ﻟﻠﻧﻣوذج و ﯾﻔﺗﻘر إﻟﻰ دﻣﺞ اﻟﻧﺳﯾﺞ اﻟطﺑﯾﻌﻲ ﻟﻠطﯾن ﻣﻊ اﻟﻣﻌﺎدن اﻟطﯾﻧﯾﺔ اﻟﻣﺗﻌددة، واﻟطﻣﻲ و ﺷواﺋب اﻟرﻣل، اﻟﺻدوع ﺻﻐﯾرة، واﻻﺳﻣﻧﺗﯾﺔ، وﻋﺎﻟﯾﺔ اﻟﺗﺻﻠب، واﻟﻣﯾزات اﻷﺧرى. ﯾﺗﻛون ھذا اﻟﺑﺣث ﻣن أرﺑﻌﺔ ﻣﺳﺗوﯾﺎت رﺋﯾﺳﯾﺔ ﻟﻠﺗﻐﻠب ﻋﻠﻰ ھذه اﻟﺗﺣدﯾﺎت؛ )أ( اﺧﺗﺑﺎر اﻟﻣﺳﺗوى اﻟﻛﻠﻲ، )ب( اﻟﺗﺻوﯾر واﻟﺗﺣﻠﯾل ﻋﻠﻲ اﻟﻣﺳﺗوى اﻟﺟزﺋﻲ، )ج( اﻟﻣﺣﺎﻛﺎة اﻟﺟزﯾﺋﯾﺔ، و )د( اﻟﻧﻣوذج اﻻﺳﺎﺳﻲ. ان ﻟﻠﺳﻠوك اﻻﻧﺗﻔﺎﺧﻲ ﺗم ﻋﻣﻠﺔ ﺑﺎﺳﺗﺧدام ﻣﻔﺎھﯾم اﻟﻣﯾﻛﺎﻧﯾﻛﺎ اﻟﺟزﯾﺋﯾﺔ ) (، واﻟدﯾﻧﺎﻣﯾك MM اﻟﻧﻣذﺟﺔ اﻟﺟزﯾﺋﯾﺔ CECs (. وﺟﻣﻌت ﻧﺗﺎﺋﺞ اﻟﻣﺣﺎﻛﺎة اﻟﺟزﯾﺋﯾﺔ اﻟﻣﺗﻌﻠﻘﺔ ب MC(، و ﺗﻘﻧﯾﺔ ﻣﺣﺎﻛﺎة ﻣوﻧت ﻛﺎرﻟو )MDاﻟﺟزﯾﺋﯾﺔ ) اﻟﻣﺧﺗﻠﻔﺔ، اﻟرطوﺑﺔ ،اﻟﻛﺛﺎﻓﺔ ،اﻟﻛﺎﺗﯾوﻧﺎت اﻟﻘﺎﺑﻠﺔ ﻟﻼﺳﺗﺑدال، ﺗﺎﺛﯾر اﻟﻣواد اﻻﺳﻣﻧﺗﯾﺔ ﻟﺗﺷﻛﯾل ﻧﻣوذج اﻟﻧﺎﻧو وذﻟك ﻟﺗﺣدﯾد إﻣﻛﺎﻧﯾﺔ اﻧﺗﻔﺎخ اﻟﺗرﺑﺔ اﻟطﯾﻧﺔ اﻟﻘﺎﺑﻠﺔ ﻟﻼﻧﺗﻔﺎخ. ﺗم اﻟﻌﺛور ﻋﻠﻰ ان اﺳﺗﺧدام ﻧﻣوذج اﻟﻧﺎﻧو ﻟﻠﺗﻧﺑؤ ﻋﻠﻰ إﻣﻛﺎﻧﯾﺔ اﻻﻧﺗﻔﺎخ، واﻟﻛﺛﺎﻓﺔ اﻟﺟﺎﻓﺔ اﻟﻧﮭﺎﺋﯾﺔ، وﻣ ﻠﯾﮭﺎ ﻟﻠﻌﯾﻧﺎت اﻟﺗﻲ ﺗم اﺧﺗﺑرھﺎ ﻓﻲ ﺣﺗوﯾﺎت اﻟرطوﺑﺔ اﻟﻧﮭﺎﺋﯾﺔ ﻗرﯾﺑﺔ ﺟدا ﻟﻠﻧﺗﺎﺋﺞ اﻟﺣﺎﺻل ﻋ اﻟﻣﻌﻣل. وﻟذﻟك، ﻓﺈن اﻟﺳطوح واﻟﻣﻌﺎدﻻت اﻟﺗﺄﺳﯾﺳﯾﺔ اﻟﻣﺳﺗﻧﺗﺟﺔ ﯾﻣﻛن اﺳﺗﺧداﻣﮭﺎ ﺑﺷﻛل ﺷﺎﻣل ﻟﻠﺗرب اﻻﻧﺗﻔﺎﺧﯾﺔ ﻣﻊ xxiv ، وﻣﺣﺗوى اﻟﻣﺎء، واﻟﻛﺛﺎﻓﺔ، وﻣﺟﻣوع CEC ﻛل ﻣن اﻟطﯾن وﻏﯾر اﻟطﯾن اﻟﻣﻌدﻧﻲ و اﺣﺗﻣﺎﻟﯾﺔ اﻟﻣزﯾﺞ اﻟﻣﻣﻛن ﻣن اﻟﻛﺎﺗﯾوﻧﺎت، واﻟﻛﺎﺗﯾوﻧﺎت اﻟﻘﺎﺑﻠﺔ ﻟﻼﺳﺗﺑدال. ھذا اﻟﻧﻣوذج ﯾﻣﻛن ﺗطﺑﯾﻘﮫ ﻟﺳﻠوك اﻟطﯾن او اﻟﺗرﺑﺔ ﻓﻲ اﻟﻣﺟﺎﻻت اﻻﺧرى ﺑﻣﺎ ﻓﻲ ذﻟك اﻟﺟﯾوﺑﯾﺋﯾﺔ ، واﻟﻣﺳﺗﺣﺿرات اﻟدواﺋﯾﺔ، واﻟزراﻋﺔ، واﻟﺟﯾوﻟوﺟﯾﺎ، وھﻧدﺳﺔ اﻟﺑﺗرول.
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