以定流量幫浦法量測乾溼側之土壤水分特性曲線

Measurement of Drying and Wetting SWCCs by Flow Pump Method

李柏廷(Po-Ting Li)

指導教授 ： 葛宇甯

國立臺灣大學/工學院/土木工程學研究所/碩士(2018年)

https://doi.org/10.6342/NTU201803724

摘要

大多數的大地工程師都使用傳統的土壤力學來解決大地工程的問題，由Karl Terzaghi提出的土壤力學中都是基於土壤是完全乾燥或是飽和的假設下。但是在很多現地狀況都是屬於不飽和土壤，若是使用傳統的土壤力學進行分析，便會造成不當的大地工程設計，因此了解不飽和土壤力學是必要的。不飽和土壤力學在基本分為三個部分，包含了不飽和土壤力學的理論部分、量測不飽和土壤基本性質的實驗方法和模擬不飽和土壤力學行為的方法（Chen, 2017）。其中土壤水分特性曲線（SWCC）在不飽和力學中扮演了一個重要的角色，SWCC是由含水量和土壤吸力所組成的，每一種不同的土壤都有其獨特的SWCC。在過去的幾十年中，有許多學者提出室內實驗和現地試驗來量測SWCC，這些方法包含了濾紙法、離心機試驗、張力計試驗和壓力鍋試驗。其中壓力鍋試驗已經被廣泛的使用，因為其步驟較為簡易且實驗結果有一定的可靠性，但是在壓力鍋試驗中判斷試體是否達到穩定的唯一方法是觀察其排水的狀況，為了確保試體達到飽和，所以實驗的過程就會拉長，為了改善這個問題，才提出了幾種新的量測SWCC的方法。
　　流量幫浦法（Flow Pump）是由Olsen在1966年提出來的，此方法首先應用於改善滲透係數的量測。在1991年Zindarcic等人提出了Maintained Suction Measurement和Hwang在2002年提出的Suction Drop Measurement兩種方法將流量幫浦運用到了量測SWCC的方法之中。在2011年Lee等人將兩個方法做出來的結果進行比較，分別對兩種發法列出其優點和缺點的部分，我們希望可以留下兩個方法的優點就是能有效的縮短實驗時間並且得到較好的實驗結果，所以我們提出了新的方法叫定流量幫浦法。

關鍵字

流量幫浦法 ； 吸力下降量測 ； 土壤水分特性曲線 ； 基質吸力 ； 軸轉換技術

並列摘要

In general, geotechnical engineers use soil mechanics which pioneered by Karl Terzaghi to solve various kinds of geotechnical engineering problems. The assumption of the soil is either completely saturated or completely dry in this theory. However, there are many area is in unsaturated condition and many geotechnical engineering problems occurs in unsaturated condition. Therefore, understanding the unsaturated soil mechanics could prevent the improper design happen.
The soil-water characteristic curve (SWCC) play an important role in unsaturated soil mechanics. The SWCC represent the relationship between soil suction and soil water content. There are many methods and laboratory tests have been developed to evaluate and measure the SWCC over past decades. Among them, ASTM pressure plate test is widely used since its convenience and reliability. However, the experimental duration is too long about 1~3 months to obtain a SWCC and the specimen is stable or not is difficult to determine.
In this study, flow pump system, triaxial system, 3D printing technology, axis translation technique and modified suction drop method are combined to establish an experimental system of SWCC measurement method. Fine quartz sand, Vietnam quartz sand and Peng Hu calcareous sand are used as test material for this research. Results show that this experimental method is able to obtain the SWCC efficiently and cost less experimental duration.

並列關鍵字

flow pump method ； suction drop measurement ； soil-water characteristic curve ； matric suction ； axis translation technique

參考文獻

[1] Aiban, S. A. and Znidarcic, D. (1989). “Evaluation of the Flow Pump and Constant Head Techniques for Permeability Measurements.” Géotechnique, 39(4), 655-666.

[2] ASTM C1699-09 (2015). “Standard Test Method for Moisture Retention Curves of Porous Building Materials Using Pressure Plates.”

[3] ASTM D6836-02 (2008). “Standard Test Methods for Determination of the Soil Water Characteristic Curve for Desorption Using Hanging Column, Pressure Extractor, Chilled Mirror Hygrometer, or Centrifuge.”

[4] Fredlund, D. G. (2006). “Unsaturated Soil Mechanics in Engineering Practice.” Journal of Geotechnical and Geoenvironmental Engineering, 132(3), 286-321.

[5] Fredlund, D. G. and Rahardjo, H. (1993). “Soil Mechanics for Unsaturated Soils.” New Jersey, John Wiley & Sons, Inc.