不等向壓密飽和砂土之動態變形行為

Dynamic deformation behavior of saturated sandy soils under anisotropic consolidation

曾正豐(Cheng-feng Tseng)

指導教授 ： 黃俊鴻

國立中央大學/工學院/土木工程學系/碩士(2011年)

摘要

本研究利用動力三軸試驗儀器量測飽和石英矽砂之動態強度試驗，主要在求得不同相對密之石英矽砂試體在等向及不等向壓密條件下之動態強度曲線。本研究控制有效圍壓為0.5及1.0 kg/cm2，進行等向壓密Kc=1.0及非等向壓密Kc=1.5和Kc=2.0狀態下三種不同相對密度之動力三軸試驗，以探討石英矽砂於不同壓密應力比下及不同相對密度下的孔隙水壓、軸向變形行為及動態強度曲線之特性，作為分析液化地盤變形行為之參考。
試驗結果顯示在等向壓密下，施加反覆應力越大所激發之極限孔隙水壓比越低，在非等向壓密下，施加反覆應力越大所激發之極限孔隙水壓比越大，當壓密應力比越大受動態荷載作用下所激發之極限孔隙水壓比越小。石英矽砂之動態剪應力比隨著相對密度及壓密應力比增加而增加，但隨著有效圍壓的增加而下降。本研究並將試驗結果整理成不同相對密度及壓密應力比下反覆剪應力與剪應變及反覆軸差應力與軸向應變關係之關係，可用於估計土壤受震所產生之動態變形量。

關鍵字

相對密度 ； 動力三軸試驗 ； 有效圍壓

並列摘要

The saturated soils beneath shallow foundation are in an anisotropic consolidation state before earthquake. Their dynamic behaviors are closely related to building settlement located in a liquefaction-susceptible ground. This study performed a series of cyclic triaxial tests on isotropically and anisotropically consolidated remolded quartz sands to deduce the residual deformation characteristics. The test conditions being varied include the relative density, the confining pressure, and the anisotropic consolidation ratio Kc. The test results show that the higher the relative density and the lower the confining pressure, the smaller the deformation deduced. The larger the Kc, the more the residual deformation and the less the cyclic component. It is also found the residual deformation of soil sample loaded first with compressive force is larger than that of soil sample loaded first with tensional force. The difference of the above two residual deformations can be used to assess the differential settlement of building located in a liquefiable ground.

並列關鍵字

Volumetric strain ； Excess pore pressure ； Differential settlement ； Anisotropic ； Residual deformation ； Cyclic deformation ； Liquefaction ； Dynamic triaxial test

參考文獻

9. Yasuda, N., Matsumoto, N., Yoshioka, R., and Takahashi M., “Undrained monotonic and cyclic strength of compacted rockfill material from triaxial and torsional simple shear tests,” Canadian Geotechnical Journal, Vol. 34, pp. 357-367 (1997).

10. Amini, F., and Qi, G.Z., “Liquefaction testing of stratified silty sands,” Journal of Geotechnical and Geoenvironmental Engineering, ASCE, Vol. 126, No. 3, pp. 208-217(2000).

11. Ishihara, K., and Yoshimine, M., “Evaluation of settlements in sand deposits following liquefaction during earthquake,” Soils and Foundations, Vol. 32, No. 1, pp. 173-188 (1992).

12. Hyodo, M., Hyde, A.F.L., Aramaki, N., and Nakata, Y., “Undrained monotonic and cyclic shear behaviour of sand under low and high confining stresses,” Soils and Foundations, Vol. 42, No. 3, pp. 63-76 (2002)

17. Seed, H.B., Soil liquefaction and cyclic mobility evaluation for level ground during earthquakes. J.Geotechnical Engineering Division, ASCE 105 (GT2), pp. 201-255(1979).