飽和砂土中樁基受反覆側向荷重之行為

Behavior of Model Pile in Saturated Sand Subjected to Cyclic Lateral Load

曾永成(Yung-Cheng Tzeng)

指導教授 ： 翁作新

國立臺灣大學/工學院/土木工程學研究所/碩士(2008年)

https://doi.org/10.6342/NTU.2008.00484

摘要

為了解基樁承受側向載重時樁土互制的行為，因而於國家地震工程研究中心將模型樁(樁長150 cm，外徑10.16 cm，管壁厚0.3 cm)埋置於大型剪力盒之飽和越南砂試體中進行一系列側向樁載重試驗。
試驗的內容有空箱單樁及土壤中模型樁側推試驗，加載的形式有靜態及反覆荷載。反覆加載位移波型為正弦波，加載頻率為0.5、1與2 Hz，最大側向位移量為1至5 mm。應用測微錶、樁身上黏貼之應變計與土壤中之水壓計量取在不同加載情況下，樁身及土壤之反應。
經由空箱單樁側推試驗之彎矩-曲率關係圖得知，樁身呈現線彈性材料之行為，在不同加載條件下，樁頭勁度一致。土壤中模型樁試驗之樁頭勁度隨著位移增加而減少，隨著頻率的增加而增加。樁頭阻尼比則會隨著變位增加而增加，隨著頻率的增加而減少。由量測樁身變形數據所求得之p-y曲線變形模數會隨深度增加而增加，不同頻率試驗之p-y曲線變形模數差距會隨著深度增加而增加。樁身受側推時，超額孔隙水壓激發主要集中在樁周附近。樁移動時土壤受壓區之超額孔隙水壓力呈正值，而土壤拉張區之超額孔隙水壓力則表現出負值。當側推至最大樁頭側向位移時，在樁移動時土壤受壓區所量測到的超額孔隙水壓有減少的趨勢。

關鍵字

基樁 ； 側向荷載 ； 樁土互制 ； 模型樁試驗

並列摘要

In order to understand the behavior of soil-pile interaction for a pile foundation subjected to lateral loading, a series of lateral load tests were conducted on the instrumented model pile with a length of 1.50 m﹐an outer diameter of 101.6 mm and a wall thickness of 3 mm within a saturated Vietnam sand specimen inside the laminar shear box at National Center for Research on Earthquake Engineering (NCREE).

The lateral load tests on the model pile with and without sand were performed under static and cyclic loading conditions. The input motions of cyclic loading included sinusoidal waves with amplitudes ranging from 1 mm to 5 mm and frequencies of 0.5 Hz﹐1 Hz and 2 Hz. The dial gages, strain gages and piezometers were installed at various locations to measure the responses of pile and soil under different loading conditions.

The moment-curvature relation of model pile without sand specimen presented a linear-elastic behavior in the lateral load test. The stiffness of pile top displacement of model pile in the sand specimen decreases with increase of deflection at pile top and increases with frequency. The damping ratios of the model pile within the sand specimen in lateral load test increase with increase of deflection and decrease with frequency. The p-y curves were obtained based on the measured pile curvatures along the pile. The modulus of p-y curve increases with the depth of the pile﹐and the modulus of p-y curve at the same depth of the pile increases with loading frequency. It was observed that the generated excess pore water pressure mainly occurred near the pile perimeter when the model pile subjected to lateral load. The positive excess pore water pressures were generated on the compression side of pile, while on the extension side, the negative excess pore water pressures were occurred.

並列關鍵字

pile ； lateral load ； soil-pile interaction ； model pile test ； saturated sand

參考文獻

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【9】 Funahara, H., (2008), “Components of Dynamic Subgrade Reaction on Pile in Saturated Sand”, Geotechnical Earthquake Engineering and Soil Dynamics IV, ASCE, GSP 181, pp. 65-81.