非飽和土壤乾燥保水曲線在震動環境下動態變化之研究

Dynamic Variations in the Drainage Water Retention Curves of Unsaturated Soils due to Acoustic Vibrations

楊佶欽(Chi-Chin Yang) ； 羅偉誠(Wei-Cheng Lo) ； 陳主惠(Chu-Hui Chen) ； 葉昭龍(Chao-Lung Yeh) ； 許少瑜(Shao-Yiu Hsu)

《農業工程學報》 61卷1期 (2015/03) Pp. 45-64

https://doi.org/10.29974/JTAE.201503_61(1).0004

摘要

本研究利用砂箱試驗探討砂土在乾燥過程之動態保水曲線與靜態保水曲線之差異，並探討在彈性波（聲波）的作用下，聲波震盪頻率（75 Hz、100 Hz、125 Hz和150 Hz）對於動態保水曲線的影響。根據實驗結果可知，飽和度與時間之關係曲線和飽和度變化率與時間關係曲線在固定抽水量之條件下受到聲波影響並不明顯，可視為聲波震盪不影響飽和度和飽和度變化率與時間之關係，亦說明了聲波震盪時只影響動態毛細張力和動態係數。受到聲波震盪影響之動態係數皆比未受聲波影響時之動態係數小，又以受頻率150 Hz影響的動態係數最小。利用VG模式擬合得到形狀因子α與頻率之關係，可得知形狀因子α受到聲波震盪影響而改變，又以受頻率100 Hz影響的形狀因子α最小而受頻率150 Hz影響之形狀因子α最大。這表示保水曲線中的入侵張力（entry pressure, P_d）受到聲波頻率的影響而改變，以受聲波頻率150 Hz影響之動態保水曲線的入侵張力最小。由於受到聲波影響之形狀因子α皆大於未受聲波影響之形狀因子α，這也說明了聲波震盪時容易使得空氣進入孔隙介質中。

關鍵字

動態保水曲線 ； 動態係數 ； 砂箱試驗 ； 彈性波

並列摘要

This study examines the differences between the static water retention curve and dynamic water retention curve using a sand box test. It also examins how various frequencies of sound waves (0 Hz, 75 Hz, 100 Hz, 125 Hz and 150 Hz) of sound wave would affect the dynamic water retention curve during the drainage process. The results show that the differences in the curves for the relationship between saturation and time, and the changes in saturation due to the acoustic waves under stable pumping rate are not significant. It can be assumed that acoustic vibration does not affect the curve of the relationship between the saturation and time, and the desaturation rates. This means that the acoustic waves affect the dynamic behavior of capillary tension and the dynamic coefficients. The experimental results showed that dynamic coefficients with acoustic shocks are smaller than those without acoustic shocks. Moreover, the minimum value of the dynamic coefficient is τ_(150). Using the van Genuchten model (VG model) to fit the relationship between the shape factor α and frequency, the results show that acoustic shocks affect the shape factor α, with the smallest effect seen for the 100 Hz sound wave, and the greatest effect for the 150 Hz sound waves. The results mean that the entry pressure (P_d) of the water retention curve is changed following the change in acoustic wave frequency, and that the P_d of the water retention curve is the lowest with a sound wave of 150 Hz. The results also show that an acoustic shock allows air to penetrate the porous media more easily.

並列關鍵字

Dynamic water retention curve ； Dynamic coefficient ； Redistribution time ； Acoustic waves