場鑄樁嵌入岩盤之底承力評估

Evaluation of Tip Resistance for Drilled Shafts Socketed into Rocks

陳哲(ANJERICK TOPACIO)

指導教授 ： 陳逸駿

中原大學/工學院/土木工程學系/博士(2023年)

https://doi.org/10.6840/cycu202301043

摘要

本研究採用大量且廣泛之實際樁載重試驗資料評估場鑄樁嵌入岩盤受壓載後之底承力行為模式，主要分析各代表性樁載重試驗之詮釋法與底承力預測分析方法，以探討其適用性。

在詮釋法方面，對十種代表性詮釋法進行評估比較，結果顯示這些詮釋法應用於岩盤所得到之基樁承載力大小排列與先前研究應用於一般土壤有一致的趨勢，惟其在發揮承載力所需位移方面有明顯的增大。在各詮釋法中， Terzaghi 和 Peck 方法獲得下限值，而 Chin 方法獲得上限值，L1 是彈性極限值，L2 可適宜作為詮釋場鑄樁嵌入岩盤之破壞載重。

應用目前工程界可用預測底承力之分析模式於樁載重之試驗資料，經由實際量測結果與預測值之比較分析，本研究建立各分析模式之適用性與相關性。總體而言，Zhang 預測模式與實際測量測值較為一致。同時，本研究亦建議目前各可用預測模式之適用位移範圍。最後，經由樁載重試驗資料之回饋分析，本研究亦發展更一致之分析模式於未來工程使用。

本研究同時對載重-位移曲線及其相對應之底承力行為進行不確定分析，包括底承力模型因子 Mu 和 Ms與載重-位移曲線及底承力之雙曲線模型係數a和b。分析結果顯示場鑄樁嵌入岩盤之a和b係數為具有低到中分散的程度且有明顯的負相關性。這些不確定分析之偏差和離散結果，可用於未來可靠性設計分析時作為校準相關承載力係數之用。

最後，對本研究之各分析結果均提出具體之設計建議，所有分析結果均附以統計資料，以示其可靠度及供未來規範制訂之參考。

關鍵字

樁基礎 ； 現澆樁

並列摘要

This study utilizes a large number of extensive drilled shaft load test data to evaluate the tip resistance behavior of drilled shafts embedded in rock under compression loading.
Ten representative interpretation criteria were employed and compared, and the results showed that the capacity obtained by applying these interpretation methods to the rock database produced a consistent trend with that of the previous researches applied to general soils. However, there is an evident increase in the required displacement for rock-socketed shafts. Among the interpretation methods, the Terzaghi and Peck method interprets at the lower range, while the Chin method interprets at the upper range. L1 is the elastic limit value, and L2 can be suitable to interpret the failure load of drilled shafts embedded in rock.
Applying the current models for predicting tip resistance available in the engineering field to the created database, and through the comparison and analysis of the actual measured results and predicted values, this study establishes the applicability and relevance of each prediction model. Overall, Zhang's prediction model is in good agreement with the actual measured values. This study also suggests the applicable displacement ranges of the currently available prediction models. Finally, through back analysis using the current database, this study also develops more consistent prediction models for use in future engineering designs.
Model uncertainty analysis of the load-displacement curve and its corresponding tip resistance behavior is carried out, which resulted to the model factors Mu and Ms for the tip resistance and the hyperbolic model coefficients “a” and “b” for the load-displacement curve and the tip resistance. The results show that the “a” and “b” coefficients of drilled shafts embedded in rock are low to moderately dispersed and has a strong negative correlation. The corresponding bias and dispersion results can also be used in the future to calibrate the resistance factor used in the reliability-based design.
Finally, specific design recommendations are put forward for each analysis result of this study, and corresponding results are attached with statistical data to show their reliability and provide reference for future specification formulation.

並列關鍵字

Drilled Shafts ； Rock Socket ； Load Test ； Compression Loading ； Interpretation Criteria ； Tip Resistance ； Database

參考文獻

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