Shear band theory-basedreinforcement mechanism of geosynthetics / Mohd Khairul Azhar Ismail

Geosynthetic is one of reinforcement materials which is widely used in earth retaining structures. Previous researchers have carried out many studies on the soil-geosynthetic interaction. However, research on shear band is limited because o f its presence in micro scales which also makes it difficult to be determined and predicted. This research is a new contribution for Malaysia's engineering practice. There is no such research has been conducted in our country, on the local soil. In this study, three types o f silica sand were used. The coarse sand (D5o=l.357mm), medium sand (D50=0.571 mm) and fine sand (Dso^O.286mm). Pullout test were conducted for different governing parameters such as porosity, density, mean size and normal pressure at lOOkPa, 150kPa and 200kPa. There are two types of geosynthetics which were used as reinforcement. They are biaxial geogrids and woven geotextiles. The conventional machine used is Pull out box test where size o f box is 700mm (length) X 550mm (height) X 400mm (width). The simulations of Pullout Tests were made and calibrated with the experimental study. Using Discrete Element Method (DEM), it was found that the shear bands existed in soil structure during movement of geosynthetics. Shear bands were predicted equivalent with sheared zone at the reinforced region. The higher thickness value was recorded by the simulation o f sand-geotextile interaction in coarse sand at 200kPa. The shear band is 232mm width and has a pore space at the tail o f the geotextile. Meanwhile, the lower thickness value was stated by the simulation o f geotextile-pullout in fine sand at lOOkPawhereby the band is just 88mm width. Comparatively, the percentage different is 62.07% for the wider to small shear band thickness. It can be concluded that, the higher pullout force, the thicker shear band produced.