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  • 學位論文

場鑄樁受側向載重之行為評估

Evaluation of Lateral Behavior for Drilled Shaft Foundations

指導教授 : 陳逸駿
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摘要


摘要 本研究針對場鑄樁受側向載重之行為進行分析探討,藉以提供設計上分析模式之採用的建議以及參考。利用樁之側向載重試驗結果,以詮釋法詮釋載重,並將土層分為排水土層、不排水土層以及卵礫石層,以張氏簡易側向分析,以及利用LPILE程式輔助p-y curve理論分析預測承載力。以詮釋載重為實測值與預測承載力做比較,探討場鑄樁之側向行為模式。最後與前人研究打擊樁之側向行為結果做比較,提出設計上之建議。 排水土層之場鑄樁在樁頭變位量達到25 mm以前預測承載力均低於實際載重,並且無論是張氏簡易分析或p-y curve理論,預估承載力均在25 mm時最接近實際載重。其後隨著樁頭位移量增加,預測承載力均有高估實際載重之趨勢。不排水土層之場鑄樁以p-y curve理論分析承載力以統計資料顯示有較大誤差之趨勢。張氏簡易側向分析預測承載力在樁頭位移量達30 mm時最接近實際載重,超過30 mm後即有高估之趨勢,與排水土層有較相似之趨勢。 卵礫石層本研究利用SPT-N值為50或100分別以張氏簡易側向分析預測承載力,其結果顯示若以SPT-N值為50,張氏簡易分析之預測承載力在樁頭達到30 mm變位前,均有較低於實際載重之趨勢。若以N值為100分析,樁頭位移到20 mm時最接近實際承載力,其後有高估之趨勢。p-y curve理論以有效摩擦角為41°或45°分析,預測承載力在10 mm時最接近實際載重。其後隨樁頭位移量增加,p-y curve理論預估承載力均有高估之趨勢。 由於現地基礎施工之工法不同,圓形預鑄混凝土打擊樁在排水土層之實際載重較明顯比預測值高。場鑄樁之勁度較大,在較小樁頭位移量內實際承載力均較打擊樁高。鋼管樁由於中空之緣故,勁度較小,分析上容易高估。在不排水土層,打擊樁之實際載重趨勢與場鑄樁相似。但圓形預鑄混凝土打擊樁以及鋼管樁之勁度均較小,實際載重亦為場鑄樁較能承受較大之載重。不排水土層較不受打擊樁工法影響,預估承載力之趨勢與場鑄樁之預估承載力趨勢相同。

並列摘要


ABSTRACT The lateral behavior of drilled shaft foundations under lateral loading is evaluated in this study. The measured results of drilled shaft lateral loading are compared with analysis results by Y-L Chang method and p-y curve method. The data employed are subdivided into drained soils, undrained soils, and gravelly soils. The tendency of lateral behavior for the drilled shaft using statistical analysis is presented. Meanwhile, the analysis results of drilled shafts in this study are also compared with previous analysis results for driven piles. Based on the comparison of measured and analysis results for drained soils, the predicted capacity is close to the measured capacity either using Y-L Chang method or p-y curve method while the displacement of pile head is smaller than 25 mm. While the pile head is longer than 25 mm, the predicted capacity by Y-L Chang's method is overestimated. For undrained soils, the predicted capacity by p-y curve method presents inconsistent. The predicted capacity is close to the measured capacity by using Y-L Chang method while the displacement of pile head is 30 mm. While the displacement of pile head is larger than 30 mm, the predicted capacity is overestimated. For gravelly soils, the SPT-N value with 50 and 100 is used to calculate the capacity by Y-L Chang method. It was found that the capacity is underestimated with SPT-N of 50 if the displacement for pile head smaller than 30 mm. When using the SPT-N value with 100, the predicted capacity is close to the measured capacity for the displacement of pile head is 20 mm. However, the predicted capacity is overestimated if the displacement of pile head is larger than 30 mm. In p-y curve method, the predicted capacity is close to the measured capacity while the displacement of pile head is 10 mm for either the effective stress friction angle is 41° or 45°. The predicted capacity by p-y curve method is overestimated if the displacement of pile head is longer than 10 mm. To evaluate the impact of construction method on the lateral capacity, the analysis results of drilled shafts and driven piles are compared. The differences are also concluded between drilled shafts and various types of driven pile.

參考文獻


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