場鑄樁之載重-位移關係及底承力分析

Analysis of Tip Resistance and Load-Displacement Relationship for Drilled Shafts

林杰慶(Jie-Cing Lin)

指導教授 ： 陳逸駿

中原大學/工學院/土木工程研究所/碩士(2015年)

https://doi.org/10.6840/cycu201500937

摘要

本研究蒐集國內外黏聚性及非黏聚性土層之場鑄樁樁載重試驗資料，分析樁之載重位移關係及底承力公式。為評估場鑄樁之極限試驗承載力，本研究所選取之載重試驗均為變位較大且同時有沿樁身應力分佈曲線圖，經由分析整理繪製場鑄樁之典型載重-位移關係圖。因基樁之底承力發揮程度受到樁長與土壤強度之影響，在分析載重位移關係時本研究更以樁之長徑比、SPT-N值與底承力發揮程度之統計分析結果，依基樁底承力發揮大小分為兩大類評估，使統計分析更為精確。
透過極限試驗承載力與承載力理論公式之比較，非黏聚性土層之理論預測承載力高於實際量測承載力數倍，因此本研究進一步藉由修正其中之分析參數以使理論預測值能與實際量測值趨於一致。為達到此目的，本研究使用最佳化分析修正各分析係數，建立出一套新的承載力公式。新的承載力公式在分析時，分別包含為無臨界深度及有臨界深度之觀念。本研究所建立之場鑄樁於非黏聚性土層之修正承載力公式運用於工程案例，可增加理論承載力預測之精確度。

關鍵字

場鑄樁 ； 載重-位移曲線 ； 黏聚性土層 ； 非黏聚性土層 ； 底承力

並列摘要

A large number of drilled shaft load test data are applied to evaluate the load-displacement relationship and tip resistance, and these data are divided into drained and undrained soils. To analyze the ultimate bearing capacity, all collected load test data have both large displacement and load distribution curve along shaft. By statistical analysis, the typical load-displacement curve is established. Because the mobilization of tip resistance is affected by the shaft depth and soil strength, these load tests are further divided into two sub-groups for the analysis of load-displacement curve based on the shaft depth/diameter, SPT-N value, and ratio of tip resistance. With such classifications, more representative load-displacement curve can be reached.
Comparing measured and predicted tip resistances of drilled shafts, it is found that the predicted tip resistance in drained soils is much larger than measured results. Therefore, the analysis coefficients used in drained soils are modified to make a consistent result for measured and predicted tip resistances. In the improvement of tip resistance, the methodology of optimization was used and the aspects of critical depth and no critical depth are considered in this study. Finally, this study suggested a new analysis equation that can better evaluate the tip resistance and be reliably applied in engineering practice.

並列關鍵字

drilled shafts ； load-displacement relationship ； drained soils ； undrained soils ； tip resistance

參考文獻

26. 吳浩瑋(2011)，「樁基礎於排水土層之樁底承載力分析模式研究」，碩士論文，中原大學土木工程研究所，桃園中壢。

25. 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。

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