Study on Large-Scaled pullout behaviors of Geogrid with Sand Confinement by Diffrent Test Conditions

• Main Author: 張芳清
• Other Authors: 張達德
• Format: Others
• Language: zh-TW
• Published: 1997
• Online Access: http://ndltd.ncl.edu.tw/handle/69224506588212824161

碩士 === 中原大學 === 土木工程學系 === 85 === 　　Earth reinforcement has been widely used in Taiwan in recent years. Direct shear test and pull-out test are commonly applied to determine the mechanical propoerties at the interface between the soil and reinforcement. Many factors can affect the results of pull-out test; and they mainly come from three aspects, the test device, the soil specimen, and the reinforcement specimen. This study researches some of these concerns in laboratory tests. 　　Four types of geogrids and one type of sandy soil are used in this study, in conjunciton with a large-scale pull-out testing device. To eliminate the boundary effects on the accuracy of the pull-out test, a series of pull-out tests have been carried out using different sleeve lengths, different geogrid specimen widths, and different displacement rates. Earth pressure cells are installed for monitoring purpose at suitable locations at the front and lateral walls of the shear box. The length of the shear box is varied from 1.5m to 2.5m to fit geogrids of 1.0m, 1.5m, and 2.0m in length, in order to perform the pull-out test. To measure the deformation of geogrid, steel hooks and inextensible tell-tale wires are attached to the nodes of the geogrids with the displacement transducers located outside the shear box. 　　Findings indicate that the boundary effect has a significant impact on the results of the test, and it should be adequately regulated by sleeve length and width of specimen. Different displacement rates show different strength transmission mechanisms. Stiff geogrid of low extensibility is more capable of transferring tension exerted on it to the free ends than is a flexible geogrid. Deformation of the flexible geogrid centered at the pull end, and the associated tension onit, are completely non-uniform. As long as the anchor strength is sufficient, geogrids all exhibited a rupture failures. In this condition, an increase in geogrid length has a small effect on pull-out behavior; however, the deformation of the geogrid is distributed more evenly towards the free ends and the pull-out interaction coefficient decreases accordingly.