土釘加勁技術主要靠密集的土釘打設，使土釘與周圍土壤形成一連貫性實體，並利用土釘抗張的特性對邊坡產生約束作用，然密間距情況下可能導致土釘周圍應力影響範圍重疊，而造成拉出阻抗下降。有鑑於此，本研究進行不同埋設間距下之四釘拉出試驗，以試驗結果探討影響範圍於各種重疊情況與群釘效率的關係。另進行五釘試驗，以更為繁複之影響範圍重疊情況，配合四釘試驗結果探討與陳韋成(2007)三釘及本研究五釘試驗結果的關係。此外，更整合前人雙釘試驗結果，建立影響範圍單一重疊模式，並將群釘影響範圍多重重疊應用於此模式，最後探討重疊效應對群釘拉出阻抗之關係。 經由試驗結果及經驗模式分析得到以下結論：(1)透過粗糙因子(R)，及雙釘互不影響之最小間距，整理出各尺寸土釘於編號201砂土中的影響範圍；亦透過繪圖軟體(AutoCAD)配合影響範圍，精準找出試驗規劃各埋設間距之四釘及五釘影響範圍重疊情形。 (2)土釘直徑相同，牙距越大則其影響範圍越大；牙距相同，土釘直徑越大則影響範圍越小。(3)透過三種影響範圍重疊情況，對四釘於各埋設間距下之群釘效率-影響範圍重疊率之探討結果得知，影響範圍多重重疊所導致的群釘效率衰減，呈略為線性的遞減關係，而此趨勢亦存在於前人之三釘拉出試驗結果，以及本研究之五釘拉出試驗結果。且顯示影響範圍多重重疊時，群釘效率於三次重疊以上略低於單一重疊之情況(約8%)，因此在多重重疊情況下，亦可應用單一重疊之關係。 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.
