- 學位論文
風化泥岩的水力侵蝕過程與機制
The Process and Mechanism of Water Erosion on Mudstone Regolith – a case study in Taiwan
摘要
臺灣面臨極端降雨與氣候乾旱並存的天氣型態，可預見的未來，土壤流失的問題將會逐漸嚴重，不僅影響土地利用方式亦會造成地質災害，若能掌握土壤侵蝕，尤其是侵蝕過程與機制將有助於水土保持工作進行與後續科學研究之用。 本研究可分為室外降雨模擬實驗與室內水槽沖蝕實驗，室外實驗利用人工降雨機模擬高強度的降雨事件，選在臺南市龍崎區的泥岩邊坡進行土壤沖蝕實驗，並利用地面光達資料製作高精度數值高程模型，用於重建侵蝕過程並量測土壤侵蝕量。考慮野外實驗難以模擬逕流對泥岩風化層的侵蝕作用，所以於室內實驗設計沖蝕水槽，利用樣區所採集的泥岩風化層為材料，模擬地表逕流侵蝕，配合地面光達測繪技術，記錄地表形態受侵蝕後的逐時變化。 研究結果顯示：(1)泥岩邊坡風化層水力侵蝕過程可分為四個階段，a.片狀侵蝕(Sheet erosion)，約占總侵蝕量的6%；b.紋溝侵蝕(Rill erosion)，約占總侵蝕量的54%；c.崩塌(Failure)，約占總侵蝕量的28%；d.穩定(stable)，約占總侵蝕量的12%。(2)有泥裂(mud-cracks)的沖蝕量比無泥裂的邊坡高125%，侵蝕速率快120%。(3)泥裂會影響紋溝發育形貌。(4)初期逕流沉積物濃度可達16g/ml，隨後降低至2-3 g/ml，隨後則會因紋溝發育而略有上升至4-5 g/ml。(5) 泥岩吸水回脹無論在土體乾燥或濕潤狀態，皆會影響邊坡侵蝕過程。(6)風化泥岩係母岩風化後的產物，且泥岩邊坡侵蝕具有侵蝕限制，故母岩需要經過數次乾燥－濕潤風化過程才得以產生足夠厚的風化泥岩讓蝕溝發育。
並列摘要
In recent years, the whole world is facing the extreme rainstorm or drought due to global warming. For drought condition, the common micromorphology on dry soil is mud-cracks. It might cause serious problems on soil loss during high intensity rainstorms. It not only affects land use but also reduces slope stability. Therefore, for soil and water conservation, it is necessary to clarify the factors which may cause erosion, such as crack on soil erosion that we do not confirm yet. This research aims to simulate rill development by hydraulic flume and artificial rainfall simulator to understand the influence of micromorphology on erosion process. Mudstone specimens sampled from the mudstone area of Long-Chi, south western of Taiwan. We used ground LIDAR to record volume of erosion and change of landform during experiment. The ground LIDAR data provides high resolution elevation value. therefore high-quality DTM can demonstrate more detail on terrain changes. Results show that: (1) The erosion pattern of mudstone slope can be divided into four types: (a) sheet erosion(b) rill erosion (c) Failure (d) stable.(2) Slopes with mud cracks caused 125% more soil loss than non-mud cracks slopes. Moreover, mud cracks caused 120% more soil loss rate than non-mud cracks slopes.(3) Mud cracks will influence the spatial distribution of rill.(4) As far as sediment concentration is concerned, the initial concentration of sediment will increase by slaking. After that it increase by rill development and failure. (5) Whether the states of sample are dry or wet, the phenomenon of swelling will affect water erosion. (6)The evolution of landform on mudstone slope has restriction of erosion. The existing landscape of badland might through the several drying - wetting succession.