釘-土界面阻抗能力為土釘研究領域近年來極為熱門且重要的課題，唯其阻抗機制 理論的建立尚未成熟；本研究擬分三階段進行阻抗機制的探討。第一階段以微觀力學為 基礎，考量釘-土界面幾何特性，建構剪位移與正向位移(土釘之徑向)的剪脹模式；再依 彈塑性力學理論描述正向位移與正向應力的關係，初步建立釘-土界面剪脹理論模式， 並撰寫分析土釘拉出阻抗的計算程式。第二階段依據剪脹理論模式，納入土壤膨脹角非 定值的考量於分析的計算程式，以試驗的土釘拉出力-位移曲線結果為佐證，進行理論 預測與必要的修正，同時藉由主持人已完成針對不同砂土粒徑、土釘表面結瘤特性、土 釘直徑等因素的大量試驗結果，反算粗糙因子與剪力帶厚度的關係，建構可考量釘-土 界面不同粗糙程度的剪脹理論模式；再分別探討土釘拉出過程土壤膨脹量、正向應力增 量以及剪力帶厚度的變化，並與文獻已發表的結果比較與剖析；此外，亦以此理論模式 進行參數研究，分別探討實驗不易進行的參數，如：土釘直徑、土壤顆粒尺寸、膨脹角 以及覆土壓力等因素，詮釋各因素對土釘拉出阻抗的影響，分析結果也將與現地的拉出 試驗結果相互驗證。第三階段基於前述的理論模式，擴充應用於解釋釘與釘的互制行 為；增加考量鄰釘應力干擾下的剪脹模式，並以前兩年已完成的計算程式，再增添撰寫 分析群釘下的拉出阻抗計算程式，評估密間距群釘之拉出阻抗的衰減行為。理論分析結 果亦將與前期計畫(尺寸效應對雙釘與群釘拉出行為影響之研究)的試驗比較，並進行各 條件下的群釘參數研究，完成能充分描述粗糙釘-土界面剪脹機制的理論模式、界面阻 抗的計算程式，及其工程上預測的應用。 The research into the resistant capacity at the soil-nail interface capture attention in recent years, the theoretical mechanism is due to establish yet. A dilative mechanism is proposed in the present study and the pursuit of the theoretical development is divided into three phases. The investigation of the microstructure behavior for the soil-nail interface constitutes the first phase of the study; the dilative mechanism cause by the shear strain will be established. A computer code is written to implement the theoretical establishment. At the second phase, value of the dilative angle of the granular soil is considered to be varied with the shear strain. The proposed theoretical model will be verified using results obtained from experimental tests to pullout of nails. Results from experimental tests on nails with various particle size, nail asperity and nail diameter are used to back-calculate relationship between surface roughness factor and shear zone thickness. A dilative mechanism for the roughed-surface nail and granular soil is established, expansion of the neighboring soil and increment of radial confining stress acting on the nail can be evaluated. The theoretical model will be used to carry out a series of parametric study and to validate published results from experimental tests. The third phase of the study will center on extending the proposed mechanism to investigate interactive behavior between neighboring nails. The results from previous experimental tests on double nails, superposition of shear stresses for closed-space nails results in a reduction of pullout resistance, will be validated using the extended model.
