A laboratory study on pull-out resistance of geogrid in clay soil

Abstract

Geosynthetics such as geotextiles, geogrids and geocells are outstanding materials for reinforcement of soils. Recently, reinforcing the clay soils with geosynthetics, by increasing the bearing capacity and decreasing over consolidation, was used increasingly in geotechnical applications. The behavior of soil with reinforced material is crucial on design of reinforced soil. In this study the interaction between geogrid and clay soil was investigated by pulling out the geogrid experimentally with the help of direct shear tests machine. In experiments the geogrid was placed on shear surface that was the midpoint of test mold. The soil samples were prepared with different water content that was including optimum water content (OWC). A special cap was designed to pull-out the reinforcing material through the soil sample. According to experimental results, the variation of pullout load against displacement seems to be similar to classical load-displacement behavior of soil and it increases when the normal stress increases. Under the same normal stresses, pull-out load observed to be greater when the soil sample has OWC. At stress level σ = 27,2 kPa, when water contents of soil samples increase 60%, the pull-out loads increase approximately 30%. These observations can be interpreted the interlocking between soil and geogrid is stronger if the water content of soil samples are equal to OWC. It is also showed from the tests results that pull-out load values are generally greater than interfacial strength of soil samples.