以動態離心模型試驗模擬液化地盤淺基礎建築物之受震反應

Centrifuge modeling on seismic responses of building with shallow foundations in liquefiable ground during earthquakes

邱吉爾(Ji-Er QIU)

指導教授 ： 黃俊鴻 ； 李崇正

國立中央大學/工學院/土木工程學系/碩士(2012年)

摘要

本研究設計三種不同樓層數(1、3、5層樓)重量之淺基礎建築物模型，利用中大地工離心機於50g離心力場下進行模型試驗，並藉由試體中安裝之加速度計、孔隙水壓計、土壓力計、線性差動可變變壓器(LVDT)、雷射位移計及淺基礎建築物上之應變規，分別量測各項物理量之受震歷時，探討淺基礎建築物於液化地盤上之受震反應。
研究結果顯示:(1) 砂土試體在土壤未達液化狀態時，有明顯加速度振幅放大效應，但當地盤產生液化現象時，液化層會阻隔振波的傳遞，對建築物有振動衰減之反應；(2)建築物越重時，受振後所產生的沉陷量會越大；(3)建築物之沉陷會隨輸入振動的增強而增加，且大部分的沉陷都在振動期間所產生；(4)當施加振動越大時，液化層的深度會越深，且土層液化狀態維持時間較長，超額孔隙水壓消散所需的時間也較為長久；(5)在離心模型試驗中，使用黏滯流體作為砂土試體之飽和液體，可使超額孔隙水壓的激發與消散更為真實模擬現地之情況。

關鍵字

淺基建築物 ； 地工離心機 ； 加速度放大效應 ； 超額孔隙水壓

並列摘要

This research is a project for studying post-earthquake settlement and deformation behavior of buildings with shallow foundations in liquefiable ground using dynamic centrifuge tests. In this research, a centrifugal scale-down model was specifically designed and tested at 50g. The model buildings used in the study have three different weights and in the different sand beds saturated with water and viscous fluid, respectively. Several accelerometers, pore water pressure transducers, linear variable differential transformer (LVDT), laser displacement sensor, and earth pressure cells were installed to measure the seismic response, the generation of pore water pressure in the surrounding soil during shaking and the displacement histories of the surface settlement and of the building during shaking.
According to the analysis of model test results, the following conclusions
are made: (1) In liquefiable ground, liquefied layer will barrier vibration pass to cause buildings vibrate will be decreased. (2) On post-earthquake, the heavier buildings settlement will be larger. (3) Buildings settlement increased with the input vibration increase. (4) The liquefied layer depth increased with the input vibration increases.

並列關鍵字

shallow foundation ； liquefiable ground ； dynamic centrifuge tests

參考文獻

18. 中華民國大地工程學會，建築物基礎構造設計規範，中華民國大地工程學會(2001)。

1. Stewart, D.P., Chen, Y,R., and Kutter, B.L., “Experience with the Use of Methylcellulose as a Viscous Pore Fluid in Centrifuge Models,” Geotechnical Testing Journal, Vol. 21, No. 4, pp. 365-369 (1998)

2. Liu, L., and Dobry, R., “Seismic Response of Shallow Foundation on Liquefiable Sand,” Journal of Geotechnical and Geoenvironmental Engineering, Vol. 123, No. 6, pp. 557-567 (1997).

3. Gajan, S., Kutter, B.L., Phalen, J.D., Hutchinson, T.C., and Martin, G.R., “Centrifuge modeling of load-deformation behavior of rocking shallow foundations,” Soil Dynamics and Earthquake Engineering, Vol. 25, pp. 773-783 (2005).

5. Dashti, S., Bray, J., Riemer, M., and Wilson, D., “Centrifuge Experimentation of Building Performance on Liquefied Ground,” Geotechnical Earthquake Engineering and Soil Dynamics IV (2008)