Estimation of Pullout Curve of Reinforced Earth Using Hyperbolic Function

Pullout parameters mean the pullout friction angle and the pullout cohesion between soil and the reinforcement while the reinforcement embedded in the soil be pulled out and these parameters include the passive resistance as well as the friction resistance. And they make an important role in calculating the horizontal length of the reinforcement and the vertical distance of reinforcements in the reinforced earth wall. Pullout parameters are generally determined from pullout curves by pullout test which is a kind of big model test. However pullout tests give often inaccurate results because it is very difficult to remake the model ground with the same properties for several tests. In this study a new test method has been developed, named a staged pullout test. Present pullout test needs the production of model grounds more than three times for obtaining pullout parameters. However in a staged pullout test, only one model ground is needed. With one model ground, pullout tests are performed repeatedly, changing vertical loads after stopping a test when reaching about 2cm of pullout displacement. Hyperbolic function has been used as a method of estimating the entire pullout curve from 2cm of pullout curve, And in order to investigate the validity of a staged pullout test, both a present pullout test and a staged pullout test, have been performed about the same properties of model ground made with Korean standard sand and Geogrid. Test results has showed that a staged pullout test has a possibility to be used as a new pullout test method instead of a present pullout test.