- 學位論文
以大型直剪試驗探討地工格網/土壤互制行為之研究
Study of geogrid/soil interaction behavior by large-scale direct shear test
摘要
以大型直剪試驗量測不同土壤與地工合成材料相關的界面摩擦係數已被廣泛的使用於大地工程結構物設計中，但大多數的直剪試驗研究通常皆採用上下剪力盒內填裝同一種顆粒性材料進行直剪試驗，於設計使用上常因現地施工需要有不同的改變，因此上下不同土壤性質的介面摩擦特性的研究仍然是缺乏的。因此本研究將針對上下試體盒置入不同土壤，並於界面鋪設不同材質地工合成材料，探討不同地工合成材料與不同上下盒土壤配置進行摩擦特性研究，並研究土壤顆粒尺寸與格網開孔大小之關係、不同上下盒土壤配置之剪力研究、格網被動阻抗評估。 試驗結果得知在上盒台中港砂/下盒混凝土塊體，其影響界面摩擦角與剪力強度差異是與格網橫向勒條數，開孔大小有關格網橫向勒條數越多且網目越小，土壤與格網互制行為越為明顯，剪應力將隨著剪力位移的增加而增加，界面摩擦角將會提高。而台中港砂/紅土試驗結果顯示，纯砂尖峰剪力強度皆大於任何地工格網約8~11%，使用任何種類格網其尖峰剪力強度差異不大，並且地工織布、地工止水膜尖峰剪力阻抗是比純土壤來的小約7~43%，主要原因為地工織布、地工止水膜表面較為平滑。觀察三分石/紅土與三分石/台中港砂試驗可發現當格網與土壤顆粒有良好的互制效益時，破壞面將會遠離格網，剪力強度相會與三分石相似，而三分石/混凝土塊體試驗中顯示影響摩擦角與剪力阻抗的主要因子為接觸面積大小，且於50kPa正向應力狀態下剪力強度與界面未鋪設地工合成材料相似。 在本研究中探討直剪試驗格網橫向勒條被動阻抗發展，結果顯示傳統公式推算出的預測值是低於量測值。本研究提供證明顯示，橫向勒條被動阻抗可提供額外的被動阻抗貢獻。
並列摘要
Using Large-scale direct shear test to measure the different soils and geosynthetics related to the interface friction coefficient has been widely used in the design of the reinforced earth structure. Most of the direct shear tests are usually used on the shear box from top to bottom with same filling materials, but in the use of design and construction in field often have different needs change, from top to bottom shear boxes filled with different soil. So the interface of friction with two different layer types of soil is still a lack of research, this study will perform several series of large scale direct shear test to realize the interface behavior of geosynthetics and soil related with soil particle size, opening size of grid and passive resistance force. Test results show that Taichung Harbor Sand (upper box)/ concrete block (bottom box), the interface friction angle and shear strength are difference, related with the size of the grid opening, the grid number of horizontal opening, Soil and the geogrid system has more obvious acts, such as the shear stress to the displacement of shear increases, the interface will increase friction angle. The Taichung Harbor sand / clay test results also show that peak shear strength of pure sand all higher than any condition with different geogrids about 8 to 11 percent, and the peak shear strength of adding geogrid layer has no significant difference. The interface friction angle of geotextile and geomembrane, their peak shear strength are lower than pure soil about 7 ~ 43%, mainly reason is smooth suface. Base on the observation of gravel / clay and gravel /Taichung Harbor sand. The failure surface will be far away from the interface surface of soil when geogrid and soil particle has good interaction. The gravel/ concrete block tests showed that the main factor effect friction angle and shear resistance is interface roughness and it has similar shear strength under 50 kPa normal stress with none geosynthetic layer. In this study, the direct shear tests found horizontal rib of geogrid can develop passive resistance force. According to the previous research, the value from formula calculation is lower than the value from the measurement in this study. The passive resistance behavior also can be obviously found in this study.
參考文獻
延伸閱讀
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