場鑄樁嵌入岩層段之樁身摩擦力評估

目前，對於嵌入岩層段之樁身摩擦力(fs)之評估是以一經驗係數(alpha)與岩心單壓強度(qu)建立關係式，而不同學者間之建議關係式具有直接與單壓強度(qu)或其根號(qu^0.5)之差異。根據現今之研究，值之範圍較大，難以取得一精準值用於設計參考，因此本研究嘗試改良現階段評估基礎入岩段之樁身表面單位摩擦力之分析模式，以提供更加精確之值作為設計參考。本研究為有效改良評估基礎入岩段之樁身表面單位摩擦力之分析模式，將藉由大量入岩基礎之實際樁載重試驗資料，並且使用原始鑽探報告提供或者運用合理之方式推估而得之岩盤地工參數以及納入岩體弱面因素(RQD)進行迴歸及統計分析，並藉由統計結果提供較完整之分析模式。為使本研究能包含各個不同載重階段，本研究之詮釋法使用L1-L2 法以及Davisson法配合t-z曲線以及載重位移曲線配合沿樁身應力分布曲線兩種方式取得樁身表面單位面積摩擦力，若原始曲線發展不足導致無法詮釋時，則使用Hyperbolic延伸法進行延伸。L1法為服務極限狀態(Serviceability limit state, SLS)，可做為底限值參考，而L2法以及Davisson法則為極限狀態(Ultimate limit state, ULS)，此詮釋結果則為極限破壞值。藉由分析統計結果可得知，分析基礎入岩段之單位摩擦力時，使用alpha與qu^0.5之關係較合適。而詮釋法方面，L1法之位移量與土壤中之基樁相同，皆發生在較小位移量，對於L2法之詮釋結果，由於詮釋結果多位於延伸段，因此造成高估現象，而Davisson法之詮釋結果則最接近目前國際間之研究範圍，因此可知Davisson法較適合用於詮釋入岩條件之基礎。而將RQD值納入分析後發現，alpha - qu^0.5之關係於各RQD分類區間有一定之趨勢存在，且相關統計資料具有一定之可靠度，因此可知將RQD納入分析，可提供更加精確之alpha值，供設計分析使用。

關鍵字

岩盤；岩心單壓強度；樁身摩擦力； RQD ；樁載重試驗；詮釋法

並列摘要

Currently, in regard to evaluating the side resistance for drilled shafts socketed into rock, it is based on the relationship between an empirical coefficient (alpha) and uniaxial compressive strength (qu). However, different scholars suggest the relationship is different between the root of the uniaxial compressive strength or without the root. According to the present research, due to the range of  value is larger, it is difficult to obtain a precise value for the purpose of design reference. Therefore, this study attempts to improve the current analytical model in order to provide a more accurate alpha value to for design reference. In interpretation criteria, this research uses L1-L2 method and Davisson method coordinating with t – z curve and load – displacement curve to get the side resistance for drilled shafts socketed into rock. Since the original development of curve was not enough, this research used Hyperbolic method to extend curve. L1 method’s value is serviceability limit state (SLS), this value is the low bound. L2 and Davisson method’s value is Ultimate limit state (ULS), this value is the limit value. From the analysis and statistical results, using  - √(q_u ) relationship will be more appropriate in terms of analyzing drilled shafts socketed into rock. In interpretation’s results, L1 method’s results occur in the smaller displacement, L2 method’s results are always overvalued, and Davisson method’s results are the closest international research range. Therefore, we can see Davisson method is more suitable for interpretation of drilled shafts socketed into rock. This study included RQD values in the analysis, the results show that alpha - qu^0.5 relationship in every RQD classification range has trend certainly and has reliable statistical results (r2).

並列關鍵字

rock ； uniaxial compressive strength ； side resistance ； RQD ； pile load test ； interpretation criteria

參考文獻

23.方顗忠 (2007)，「場鑄樁樁底承載力及壓載詮釋法之評估」，碩士論文，中原大學土木工程研究所，桃園中壢。

25.朱祖宏 (2009)，「場鑄樁於卵礫石層之軸向及側向載重詮釋法及承載力評估」，碩士論文，中原大學土木工程研究所，桃園中壢。

1.AASHTO, (1992). Standard Specifications for Highway Bridges, American Association of State Highway and Transportation Official.

4.Chen, Y.J., Lin, S.W. and Kulhawy, F.H., (2011). “Evaluation of Lateral Interpretation Criteria for Rigid Drilled Shafts,” Canadian Geotechnical Journal, Vol. 48, No. 4, 634-643.

5.Chin, F. K., (1970). “Estimation of the ultimate load of piles from tests not carried to failure,” Proc., 2nd Southeast Asian Society of Soil Engineering, 81-90.

國際替代計量

場鑄樁嵌入岩層段之樁身摩擦力評估

未授權

主題瀏覽