壁樁受壓載重之行為評估

Evaluation of Compression Behavior for Barrette Piles

朱亭昌(Ting-Chang Chu)

指導教授 ： 陳逸駿

中原大學/工學院/土木工程研究所/碩士(2012年)

https://doi.org/10.6840/cycu201200518

摘要

摘要
本研究蒐集國內外40筆壁樁載重試驗資料，依其沿樁身土層及樁底土層之土壤性質分為排水土層與不排水土層兩大類，分別以具各理論代表性且能涵蓋上、中、下限詮釋範圍的詮釋法進行軸向壓載詮釋法評估。經由評估結果的分析統計，建立各詮釋法用於壁樁的相互關係及其優劣性。再經由詮釋結果分別與由承載力理論公式計算之預測值進行比較，以驗證分析公式之合理性。
在詮釋法方面，利用內差法可推估出於排水土層L1大約發生在0.27%B (B為樁徑)及平均位移量為4.7 mm，而於不排水土層L1大約發生在0.26%B及平均位移量4.2 mm，顯示初始線性段發生在相當小之位移處。於排水土層各詮釋法與L2之平均比值為介於0.79~1.39之間，平均位移量大約落在19.1~85.8 mm之間，Chin 法為大於103.8 mm。於不排水土層各詮釋法與L2之平均比值為介於0.75~1.4之間，平均位移量大約落在23.4~109.6 mm之間，Chin 法為大於118.8 mm。依平均比值及位移量觀察，L2法在整個試樁曲線分佈中屬於一中間合理的詮釋結果，而DeBeer法所詮釋之破壞載重為最低、Chin法為最高，可當做各詮釋法之上下限值。
於承載力部份，於排水土層時量測底承力介於0.11~0.22倍預估底承力之間，量測摩擦力介於1.32~1.46倍預估摩擦力之間；於不排水土層時量測底承力介於0.63倍預估底承力之間，量測摩擦力介於0.93~0.95倍預估摩擦力之間。說明一般承載力理論公式評估壁樁樁底承載力，於排水土層有明顯高估之現象，而於不排水土層時亦有些微高估之現象。而於評估壁樁樁身摩擦力，於排水土層有明顯低估之現象，而於不排水土層時結果尚為符合。另經由回饋及統計分析，建議β法評估排水土層壁樁時之k/ko值可採用1.07，而評估不排水土層壁樁時之k/ko值可採用0.74。

關鍵字

詮釋法 ； 受壓載重 ； 壁樁 ； 連續壁 ； 底承力 ； 摩擦力

並列摘要

ABSTRACT
This study collected 40 load tests for barrette piles to evaluate the axial compression behavior. A wide variety of compression load test data are used and these data are divided into drained and undrained databases. These selected criteria represent a wide distribution of interpreted results from the lower, middle, and higher bounds. In addition, these criteria employ varied interpretation bases. The interrelationship and reliability of each interpretation model were established. The interpretation results were used to examine the analysis models of tip and side resistances.
For interpretation criteria, L1 occurs at about 0.27%B (B = shaft diameter) with mean displacement of 4.7 mm in drained soils, while L1 occurs at about 0.26%B with mean displacement of 4.2 mm in undrained soils. The results indicate that the initial linear region is in a very small displacement. In drained soils, the ratios of representative interpretation criteria, which are all compared to L2, range from 0.79 to 1.39. The displacements of these criteria locate at between 19.1 and 85.8 mm, and the Chin method is greater than 103.8 mm. In undrained soils, the ratios of representative interpretation criteria, which are all compared to L2, range from 0.75 to 1.4. The displacements of these criteria locate at between 23.4 and 109.6 mm, and the Chin method is greater than 118.8 mm. Among these criteria, the Chin method is upper bound, DIN 4026 method is lower bound, and Hirany and Kulhawy (L2) method is in the reasonable middle range.
For axial capacity, the mean ratio of measured tip resistance to predicted tip resistance is between 0.11 and 0.22, while the mean ratio of measured side resistance to predicted side resistance is about 1.32-1.46 in drained soils. The mean ratio of measured tip resistance to predicted tip resistance is 0.63, while the mean ratio of measured side resistance to predicted side resistance is about 0.93-0.95 in undrained soils. This indicates that the bearing capacity theory to evaluate tip resistance is overestimated for both drained and undrained soils. For side resistance, the analysis model is underestimated for drained soils, but it is consistent in undrained soil. Based on the results of back-calculation analysis, the suggested values of K/Ko are 1.07 and 0.74 for drained soils and undrained soils, respectively.

並列關鍵字

tip resistance ； side resistance ； interpretation criteria ； barrette piles ； diaphragm wall ； compression loading

參考文獻

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