The study of overlap effect on the pullout resistance of grouped-nail

• Main Authors: Kuo-Hsin Wang, 王國鑫
• Other Authors: Yung-Shan Hong
• Format: Others
• Language: zh-TW
• Published: 2009
• Online Access: http://ndltd.ncl.edu.tw/handle/18086749356094783826

碩士 === 淡江大學 === 土木工程學系碩士班 === 97 === Soil-nailing have been widely used in soil excavation and slope stabilization. Closely spaced nails are buried or drilled into soil to form a reinforced structure. Close space between nails then cause stresses overlap, which may reduce the effectiveness of individual nail. The purpose of this study is to investigate the relationship between the several kinds of overlapped situation and the group efficiency through the result of four-nails test. Moreover, the test of five-nails which are with more complex overlapped situation to discuss the relationship between situation of overlap and efficiency of grouped-nail. To establish the single overlap model of influenced area through the past literatures under double nail tests. The model was applied to multiple overlaps of grouped-nail to estimate the overlap effect of grouped-nail. The conclusions via the tests and analysis of experience are summarized: (1) Calculate the influenced area of each size nails in No.201 silica sand by using surface roughness factor and the minimum distance of double nails which don''t influence to each other. Find the overlapped situation of influenced area accurate using the cartography software(AutoCAD) coordination influenced area. (2) When diameter of soil-nail is the same, the influenced area is increased with increasing the screw pitch. When screw pitch of soil nail is the same, the influenced area is decreased with increasing the nail diameter. (3) Discuss the relationship between group efficiency and overlapped percentage under the four-nails pullout test which are embedded into several spacing. It revealed that the weakening of group efficiency caused by multiple overlaps present slightly the liner decreasing progressively relations, and this tendency also existed in five-nails and three-nails pullout test results. It revealed that group efficiency which overlapped in 3 times slightly was lower than the single overlap(approximately 8%). Therefore, the single overlapped model might also applied to the multiple overlapped situations.