本文應用孔彈性力學理論方程式(poroelasticity)結合線性應力應變本構關係，可求得剪力波(S波)在兩種非混合流體土壤中之傳波速度與衰退係數。本文分成兩個部分探討，第一部分主要探討孔隙間在含空氣和水兩種不可混合流體，利用十一種不同的土壤[砂土(sand)、壤質砂土(loamy sand)、砂質壤土(sandy loam)、砂質黏壤土(sandy clay loam)、砂質黏土(sandy clay)、壤土(loam)、黏質壤土(clay loam)、坋質壤土(silt loam)、坋質黏壤土(silty clay loam)、坋質黏土(silty clay) 和黏土(clay)] 地質對剪力波的影響。第二部分探討孔隙間不同流體組合空氣-水(空氣代表非潤濕流體，水代表潤濕流體)、油-水(油代表非潤濕流體，水代表潤濕流體)及空氣-油(空氣代表非潤濕流體，油代表潤濕流體)等三種含兩相不可混合流體系統之林肯砂土及哥倫比亞細砂質壤土對剪力波的影響。兩部分之震盪頻率皆採用一般地震低頻率範圍 (50 Hz~200 Hz)，且潤濕流體飽和度(S2)之範圍從0.01至0.99。
整體來說在土壤地質為砂土、壤質砂土、林肯砂土及哥倫比亞細砂質壤土的土壤地質條件下，其剪力波的波速之趨勢較為穩定，其中又以砂土在S2=0.01的情形下傳波速度為94 m/s最快。在十一種土壤地質中，除了砂土和壤質砂土之外，剪力波波速在其他九種土壤中有突然上升的現象，其主要受到流體相與固體相之間的黏滯互制參數(R11, R22)所影響，而在林肯砂土和哥倫比亞細砂質壤土在三種不同流體系統中，其波速皆隨著潤濕流體飽和度遞增而遞減，而其衰退係數則與傳波頻率比的三次方成正比。

In this study, we apply the theory of poroelasticity combined with the linear stress-strain relationship for a two-fluid system to determine the phase speed and attenuation coefficient of the shear wave in an elastic porous medium containing two immiscible fluids. This study is divided into two parts; in the first part, we discuss the effect of soil texture on the propagation and attenuation of the shear wave, where eleven different soils [sand, loamy sand, sandy loam , sandy clay loam, sandy clay, loam, clay loam, silt loam, silty clay loam, silty clay and clay] bearing the air-water mixture are examined. The second part investigates the impact of different pore fluid mixtures on the propagation and attenuation of the shear wave, including the air - water mixture (air being the non-wetting fluid, water being the wetting fluid), the oil - water mixture (oil being the non-wetting fluid, water being the wetting fluid), and the air - oil mixture (air being the non-wetting fluid, oil being the wetting fluid). In these cases, Lincoln sand and Colombian fine sandy loam are selected as illustrative examples. Five lower excitation frequencies (50–200 Hz) are carried out for numerical simulation, and the saturation degree of the wetting fluid ranges from 0.01 to 0.99.
Our numerical results show the phase speed of the shear wave behaves more stable in sand, loamy sand, Lincoln sand, and Columbia fine sandy loam, among which the sand has the greatest phase speed of 94 m / s as water saturation is 0.01. Except sand and loamy sand, the phase speed of the shear wave is observed to increase abruptly with water saturation. We find that an important cause behind this phenomenon is the viscous coupling between the fluid and solid phases, i.e. R11, R22. In addition, , it is revealed that the phase speed of the shear wave increases with an decrease in water saturation in Lincoln sand and Columbia fine sandy loam saturated by any pore fluid mixture. Lastly, a conclusion is drawn that the attenuation coefficient of the shear wave appears to be proportional to the cubic of excitation frequency.

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