الملخص الإنجليزي
Expansive soil was experienced in many locations in Oman. In this study an expansive soil from Adam was investigated and characterized experimentally. The study describes site investigations which include collection of soil samples and laboratory soil testing and results. The study also includes survey of damages to some buildings in the study area.
Adam soil was subjected to an extensive laboratory testing program included: wet sieve analysis, hydrometer, Atterberg limits; specific gravity, compaction, swelling, swelling pressure, consolidation, soil suction (total suction), pressure plate (matric suction), chemical analysis, X-ray fluorescence (XRF), X-ray diffraction (XRD), scanning electron microscope (SEM) and consolidated undrained triaxial (CU triaxial) tests.
Climate and geology of the area has a significant influence in the formation and the existence of clay soil in the study area. It was found that more than 55 % of the sample particles are fines (silt and clay) with an amount of clay of about 24%. It was also found that Adam soil is highly plastic. Liquid limit, plastic limit and plasticity index were in the ranges of 74-84%, 29-34% and 45-50%, respectively. Adam soil contains a high percentage of SiO2, Al2O3 and Fe2O3. These results were confirmed by XRF and SEM techniques. Adam soil exhibits high swelling potential which exceeded 12 % and swelling pressure of about 70 kN/m' for remoulded soil sample. Angle of friction (0) and cohesion (c) for undisturbed soil were found to be 12o and 36 kN/m2, respectively, which indicate medium stiff clay soil.
Adam soil was treated with Cement-By-Pass-Dust (CBPD), lime and cement as stabilization agents. CBPD was added in amounts of 6%, 10%, 20%, 30%, 40% and 50% by dry weight of soil. Lime and cement were added in 6% of dry weight of soil. Treated soil was subjected to various testing program. Liquid limit were determined for all CBPD mixes. It was found to be in the range of 91-73% showing that as the percentage of CBPD increases liquid limit decreases. It was found also that there is a decrease in the dry density of the soil as the percentage of CBPD increases. Also mix with 6% CBPD showed a low swelling percent of about 5% compared to around 12% for the untreated soil. Adam soil showed very low response to 6% lime since swelling exceeded 10% for this mix. The 6% cement mix showed the lowest swelling percent which was about 4.5% after 106 days and the highest value of dry density compared to all other values. Treated soil with 6% cement, 6% lime and 6% CBPD were also subjected to matric suction test through pressure plate apparatus. Mix treated with 6% cement showed high amount of water content under different matric suction whereas 6% CBPD showed less amount which can result in less swelling behavior of soil.
Finally, based on the site investigation and the laboratory testing a number of remedial measures for the existing buildings, precautions to new buildings to be constructed and further studies on Adam soil were recommended
Keywords: Adam soil, Atterberg limits, building cracks, cement, cement by pass dust, expansive soil, lime, suction test and swelling test.
