الفهرس 
2.1 IntroductionOnly 14 pages are availabe for public view
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Abstract
Expansive soil is a clay soil exposes significant changes in its volume when it absorbs or losses water. The swelling soil is a worldwide problem. It causes problems to all kind of structure. Swelling soil exists in regions where the climate is arid or semi- arid.
Several methods were developed to improve expansive soil properties. Some of these methods were reviewed in this research such as compaction control, lime stabilization, cement stabilization, gypsum stabilization, fly ash stabilization and treatment by using geosynthetics.
Two different techniques for treatment of expansive soil were used in this study. The first technique is concerning with stabilizing the soil chemically by mixing the expansive soil with lime and fly ash. The second technique is concerning with stabilizing the soil mechanically by using layers of geosynthetic materials.
The expansive soil used in this research is mainly montmorillonite and was obtained from El- Shorouk city in Egypt. In the first technique, the soil was pulverized, dried and mixed with lime or fly ash. The used lime ratios were 2, 4, 6 and 8 % while the ratios of fly ash used were 5, 10, 15, 20 and 25 %. The laboratory tests carried out on the soil- lime and soil- fly ash mixtures were Atterberg limits, compaction test, free swell test, direct shear test, CBR test, swelling pressure test, X- ray test and SEM test. The laboratory tests indicated that both lime and fly ash can use successfully in expansive soil stabilization field. The best amount of lime to use in stabilization of the investigated expansive soil is 6 % while the best amount of fly ash to use with the studied swelling soil is 15 %.
In the second treatment technique, a laboratory model made of tin and supported by steel angles (40 x 20 x 20 cm) was used for soil rewetting tests and reinforced soil tests. The soil was pulverized, dried and compacted in the model to its maximum dry density at its optimum moisture content. The results of cycle wetting and drying test indicating a reduction in soil swelling with increasing number of cycles.
The reinforced soil tests were carried out to investigate the effect of using layers of geogrid on the amount of swell and the swelling pressure acting on the footing model. The test is carried out on unreinforced soil, soil reinforced with one geogrid layer, soil reinforced with two geogrid layers, soil reinforced with three geogrid layers. The test results indicated a significant reduction in swelling pressure and the amount of swell with increasing number of geogrid layers.
A computer program ”SWELL” was designed by visual basic language to facilitate the ultimate use of empirical correlations concluded from the experimental results of expansive soil improvement. The computer program is designed to determine the soil properties before and after soil treatment. The program allows the user to compare between the different treatment methods and compare between the effect of each added percentage of stabilizer on soil properties.
A Comparison between the measured values of soil properties obtained from laboratory tests and the predicted soil properties by the SWELL program are made and it was noticed that the predicted results are in good agreement with the measured results.