| 摘要: | 土壤吸力是不飽和土壤研究中最重要的關注焦點，不同的土壤其 吸力隨含水量變化之行為略有不同，大部分自然界土壤都處於不飽和 狀態。國內道路工程中路基土壤容易受季節變化的影響，土壤常介於 乾燥與飽和之間，因此路基土壤不飽和的研究更加重要。另外緩衝材 埋入地底深處受地下水及污染物入侵，可能造成污染，利用土壤吸力 的觀念可以了解外界水分進入緩衝材情形，有利於掌握處置場的環境 變化。 本研究針對紅土與泥岩兩種路基土壤以及膨潤土、日興土兩種緩 衝材的濕化水分特性曲線進行量測，實驗結果發現：（1）使用濾紙法 及土壤吸力計來量測土壤吸力，其中濾紙法量測範圍較廣，但以吸力 計之變異性較低；(2) 路基土壤不同夯實能量下的吸力變化，以高夯 實能量的土壤其土壤吸力大於低夯實能量者，在濕化方面結果發現路 基土壤在夯實能量高時產生的濕化曲線會比夯實能量低時陡峭也會 較早進入飽和階段；（3）將緩衝材製成不同乾密度並分別製作土壤－ 水分特性曲線，發現美國土的吸力值比日興土大也代表美國土的持水 性優於日興土；（4）利用土壤－水分特性曲線求得之吸力與含水量關 係，可透過經驗公式推求不飽和滲透係數，並發現美國土的不飽和土 壤滲透性低於日興土；（5）環境溫度升高時，水的表面張力降低會造 成土壤吸力降低而使得水分不易入侵緩衝材障壁。 Soil suction always draws the most attention in the study of unsaturated soil. Because of the difference of water content, soils’ suctions differ from each other, and most of the soils in the nature are all in the state of unsaturation. In Taiwan, the subgrade soil used in the roadway constructions gets influenced easily once the season changes. Soil is often in the state between dryness and saturation, for the study of subgrade soil appears to be more critical. With the knowledge of soil suction, we can understand how groundwater penetrates into the buffer, and this helps to improve the performance of the disposal site. The present study commenced on the measurement of the water wetting characteristics curves of two kinds of subgrade soils, lateritic soil and mudstone soil, and two kinds of buffers, bentonite and Zhisin clay. The results of the experiments indicated that (1)in the measurement of soil suction by filter paper method and thermocouple psychrometer, filter paper method gauged a much wider range, on the other hand, thermocouple psychrometer had the lower variance; (2)as for the subgrade soil suction changes under different compaction energy, soil with high compaction energy had greater soil suction than the one with low compaction energy, and the wetting curve of subgrade soil under high compaction energy appeared to be steeper and also got saturated earlier than under low compaction energy; (3)comparing the soil-water characteristics curves at various density levels, it was discovered that the suction of Black Hill bentonite was greater than Zhisin clay; which implicated that Black Hill bentonite had a better water holding capacity than Zhisin clay; (4)by using the soil-water characteristics curves, the relationships between soil suction and water content were established through regression formula, and the unsaturated hydraulic conductivityof the soil can be determined; (5)under the escalation of temperature, the decrease of water surface tension caused the reduction of soil suction and made the penetration of water into the buffer more difficult. |
