الفهرس 
Chapter 1 IntroductionOnly 14 pages are availabe for public view
 |  | from | 138 |  |  |
| | | from | 138 | | |
Abstract
Soil liquefaction is a critical scientific and engineering challenge that can cause substantial damage to numerous engineering structures and infrastructure around the world. This research presents the effect of randomly polypropylene fibers and cement in improving the resistance to liquefaction and shear modulus of loose sand deposits. A series of laboratory undrained cyclic triaxial tests has been conducted as per ASTM D3999 and ASTM D5311. Cemented specimens were prepared with cement contents ranging from 0% to 5% by weight of dry sand and then cured for different curing times. The first group was not cured, while the second, third, fourth and fifth groups were cured for 3,15,30 and 60 days respectively. In this study, glass fibers and polypropylene fibers were utilized as stabilization materials. Glass fibers have lengths of 6 mm and 12 mm, whereas polypropylene fibers have lengths of 10 mm and 20 mm. The fibers were added to dry sand–cement mixtures with contents of 0 %, 0.5 %, and 1.0 % by weight. It was found that the shear modulus and liquefaction resistance of specimens increased as the fiber content, fiber length and cement content increased. The addition of 1% polypropylene fiber to 5% cement gave the best effect on specimens’ stiffness and liquefaction resistance. The percentage of increase of shear modulus of specimens increases as the cell pressure increases. The relative density has a great impact on liquefaction mitigation. As the relative density increased, the liquefaction mitigation increased as well. The duration of the curing time has a significant effect on the stiffness of reinforced sand specimens. The addition of Geofibers increased the liquefaction resistance as the number of layers increased. Finally, the fiber and cement inclusions greatly boosted the liquefaction resistance and the stiffness of sand specimens. This study proposes cement and fiber as a good soil improvement technique that can improve liquefaction resistance.