透過您的圖書館登入
IP:44.192.107.255
  • 學位論文

飽和砂土中孔隙水壓力之傳遞試驗

Laboratory tests of pore water pressure transmission in saturated sand

指導教授 : 翁作新

摘要


根據在國家地震中心的大型剪力盒飽和砂土液化試驗的結果,觀察到在淺層砂土中較深層砂土容易液化,而且水壓力在飽和土層中的傳遞有可能與液化有關,故本研究探討孔隙水壓力於飽和砂土中的傳遞情形。為觀察水壓力的傳遞情況,在本研究中設計了一套儀器與量測系統,其水壓力由試體底部激發後向上傳遞,以模擬在現地土層受震的水壓力之傳遞情形。而試驗之試體土樣為三種粒徑大小的越南石英砂。 在純水之中加速度計與水壓計量測的傳遞速度相當接近皆約為1400 m/s。而在飽和砂土層中則兩者量測方式所測得之傳遞速度會有很明顯的差異,從加速度計所量測得到之水壓力傳遞速度在空隙比約為0.69時,粗、中、細砂的傳遞速度均為1200-1600 m/s,與其他學者所量測得到的傳遞速度相當接近,而水壓計所量測到的傳遞速度為200-300 m/s。並比較細砂在不同空隙比情況下,水壓計所量測到的傳遞速度也大略相同。而砂試體在隨著敲擊的過程中會產生沉陷,但比較沉陷變化大與沉陷穩定時,兩者所量測的傳遞速度也相當接近。空隙比大約相同時,粗砂的水壓力傳遞速度較中砂與細砂之水壓力傳遞速度略為快速,其原因可能為粗砂的空隙尺寸(pore size)較大。 若考慮同一試體中水壓力變化值時,則接近水壓力產生源的試體底部最大,深度越淺水壓力值衰減越大。而在同樣的敲擊之下,細砂試體中水壓力激發值為最大。

關鍵字

飽和砂 液化 水壓力 傳遞速度 試驗

並列摘要


The results of shaking table tests for study of liquefaction of saturated sands performed at the National Center for Research on Earthquake Engineering suggested greater tendency of liquefaction in shallower sand layers. The transmission of water pressure of the shaking generated pore water pressure from the sand at the deeper depth was considered as one of the reasons for this phenomenon. Therefore, this study is to conduct an experiment for the understanding of the transmission of pore water pressure in saturated sand. To observe the transmission of water pressure, equipment and measurement system were so designed that the water pressure was excited at the bottom of a sand specimen and it transmitted upward to simulate the transmission of water pressure in a seismically excited in-situ stratum. Quartz sand with three different grain sizes was used for the soil specimens. The water pressure transmission velocity in pure water is approximately 1,400 m/s according to the measurements by both accelerometer and water pressure gauge. The transmission velocity of water pressure in the saturated sand measured by the accelerometer ranged from 1,200 to 1,600 m/s compared to 200 to 300 m/s for that measured by water pressure gauge. The transmission velocities measured by water pressure gauge in fine sand of different void ratios were about the same. Settlement occurred in the sand specimens during tests. However, it appeared that the small settlements in the specimens did not significantly affect the transmission velocity of water pressure. The water pressure transmitted slightly faster in coarse sand than that in fine sand. It is probably due to the larger pore size in coarse sand. During the tests in the sands of about the same void ratios, the pressure change was the greatest at the bottom of the specimen near where the water pressure was generated, and gradually decreased as the depth became shallower. The water pressure excitation in fine sand was the greatest among all specimens.

參考文獻


[4] Schofield, A. N. (1980) ”Cambridge geotechnical centrifuge operations,” Geotechnique 30(3), pp. 227-268.
[6] Seed, H. B., (1979) “Soil liquefaction and cyclic mobility evaluation for level ground during earthquakes,” Journal of the Geotechnical Engineering Division, ASCE, 105(2), pp. 201-255.
[8] Jafarzadeh F., and Yanagisawa. E. (1996). “Behavior of saturated sand models in multi-directional shaking table tests.” Civil Engineering Department. ToHoKu University, Sendai, Japan.
[10] Scott, R. F. (1986). “Solidification and consolidation of a liquefied sand column,” Soils and Foundations, Japanese Society of Soil Mechanics and Foundation Engineering, 26(4), pp. 23-31.
[14] Brennan, A. J. and Madabhushi, S. P. G. (2006). “Liquefaction remediation by vertical drains with varying penetration depths.” Journal of Geotechnical and Geoenvironmental Engineering, ASCE, 131(7), pp.876-885.

延伸閱讀