臺灣博碩士論文加值系統

　　近年來，加勁土壤已在台灣廣為接受與使用。評估土壤與加勁材
界面間之力學性質，於實驗室中通常以直接剪力試驗與拉出試驗為之。
針對拉出試驗而言，影響試驗結果之因素甚多，主要為試驗儀器、土
壤試體及加勁材試體三方面。本研究乃針對實驗室中較為關心的因素
加以研究。
　　本研究使用四種地工格網與一種砂土，針對自行設計之大型拉出
試驗儀，進行拉出試驗之研究。首先，探討邊界效應問題，改變套筒
長度、格網試體寬度與拉出速率，進行拉出試驗，並於前壁及側壁等
適當位置處，裝設土壓力計加以監測。其次，將原設計之側壁等適當
位置處，裝設土壓力計加以監測。其次，將原設計之試驗盒，由1.5m
加長修改至2.5m，進行格網長度1.0m、1.5m、2.0m之拉出試驗研究。
並配合以鋼鉤與鋼弦，連接格網結點與盒外之電子式位移計，以瞭解
格網之內部變形情況。
　　研究結果發現，邊界效應對試驗結果之影響甚巨，需以適當的套
筒長度及試體寬度加以控制。不同拉出速率，則有不同之力學傳遞機
制。勁度高且延展性低之硬性格網，所承受之張力向自由端傳遞的能
力較柔性格網強。柔性格網所受之拉力與變形均向施拉端集中，且極
端不均勻。大體上而言，本研究之不同格網長度拉出試驗，在錨錠強
度良好的情況下，格網均有斷裂情形發生。在此情況下，格網試體長
度增加，對拉出行為之影響程度不大，較明顯之影響在於變形向自由
端傳遞的距離增加，因而造成拉出互制係數的下降。

　　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.