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沿台灣大甲溪兩個流域的滑坡，沉積物運輸和土石流特徵;The characteristics of landslides, sediment transportation, and debris flow of two watersheds along Tachia River, Taiwan
http://ir.lib.ncu.edu.tw/handle/987654321/81774
title: 沿台灣大甲溪兩個流域的滑坡，沉積物運輸和土石流特徵;The characteristics of landslides, sediment transportation, and debris flow of two watersheds along Tachia River, Taiwan abstract: 地震是所有自然現象中最具破壞性和危險性的其中之一，因其可能產生多個裂隙、裂縫甚至同震滑坡，能對山區造成嚴重破壞。連續降雨期間許多土石流也可能發生在暴露於強烈地面震動的區域。本研究的重點是沿著大甲溪流域的土石流沉積物之搬運和沉積過程。主要使用集集地震、桃芝颱風、敏督利颱風和艾莉颱風的航拍照片。在這項研究中，圖像分析工具也被用來研究四個事件的沉積物的時空形態。儘管僅相隔2.2公里，但兩個相鄰的流域DF025和DF106對地震和強降雨事件的反應不同，因此兩個流域的沉積物演變分析方法不同。這些差異可歸因於集集地震後發生不同類型的破壞：DF025的淺層滑坡和DF106的深層滑坡。沉積物來源的差異也轉化為盆地的類型，其中DF025可以被歸類為供應限制，而DF106作為供應無限制。在研究中估計了沉積物收支，其中DF106的桃芝颱風、敏督利颱風和艾利颱風的沉積量估計分別為1.0 x 105 m3、1.4 x 106 m3 和1.1 x 106 m3。這些沉積物可以向下游運輸，並對社區造成嚴重破壞，因為只有少量土石到達大甲溪，與DF025相同。這項研究的主要目的是對沿著大甲溪土石流流域的沉積物演變分析採用半定性和半定量方法;Earthquakes are one of the most destructive and dangerous of all natural phenomena as it could generate several fractures, cracks, and even co-seismic landslides that may cause havoc in mountainous regions. A number of debris flows during sequential rainfall mayalsooccurinanareawhichwasexposedtostronggroundshaking. Thisstudyfocuses on the sediment transportation and deposition evolution of watersheds with debris flow torrents,alongTachiaRiver. AerialphotoscoveringhazardssuchasChi-ChiEarthquake, Typhoon Toraji, Typhoon Mindulle, and Typhoon Aere, respectively, were mainly used. In this research, image analysis tool was also exploited to study the temporal and spatial morphologyofthesedimentsforthefourevents. Despitebeingseparatedforonly2.2km, two adjacent watersheds, DF025 and DF106, have different reactions to the earthquake and heavy rainfall events, thus sediment evolution analysis is approached differently for the two catchments. These differences could be attributed to different types of failure that occurred after Chi-Chi Earthquake- shallow landslides for DF025 while deep-seated landslide for DF106. The differences in source also translates to the type of basin in which DF025 could be categorized as supply-limited, while DF106 as supply-unlimited. Sediment-budget were estimated in the study where DF106 has an estimated deposition volume of 1.0 x 105 m3, 1.4 x 106 m3, and 1.1 x 106 m3 for Typhoon Toraji, Typhoon Mindulle, and Typhoon Aere, respectively. These deposits could travel downstream and create havoc to communities given the right conditions since only few debris reached Tachia River, same as DF025. The main objective of this research is to have a semiqualitative and semi-quantitative approach on the sediment evolution analysis on the watersheds with debris flow torrents along Tachia River.
<br>利用有限差分法探討水力 -力學雙向耦合效應對岩盤隧道周圍地下水流之影響;Hydraulic-mechanical coupling effect on groundwater flow around rock tunnel using finite difference method
http://ir.lib.ncu.edu.tw/handle/987654321/81772
title: 利用有限差分法探討水力 -力學雙向耦合效應對岩盤隧道周圍地下水流之影響;Hydraulic-mechanical coupling effect on groundwater flow around rock tunnel using finite difference method abstract: 放射性廢棄物隧道處置的議題中，地下水於隧道壁面周圍之流動行為與流量為安全評估之重要資訊。過去的研究發現不連續面位態分布及應力的異向性會使裂隙岩體的水力傳導係數產生異向性，同時也發現裂隙力學行為中之剪脹對於隧道周圍流場的分布是不可忽略之要素，前人已透過單向耦合方法針對上述之課題進行研究，但僅單向的考慮應力對滲流場之影響。本研究將進一步探討滲流場-應力場之雙向耦合對隧道周圍流場的影響，以JRC-JCS模式計算裂隙受力產生正向閉合與剪脹之行為，並以Oda擬連續體模式計算隧道周圍水力傳導係數空間分布，再以有限差分法配合局部加密之網格得到隧道周圍的流場以及孔隙水壓，並在考慮孔隙水壓的情況下計算隧道周圍之有效應力場，疊代計算至收斂以表示滲流場與應力場間的互制作用。本研究使用之模型建立於地下650公尺深處，在考慮不同的邊界應力與裂隙分佈之異向性下，結果表示雙向耦合方法之隧道入流量相較單向耦合方法的結果約增加20%，並且於不同異向性參數下，雙向耦合方法下之剪脹區域與剪脹貢獻程度與單向耦合方法有顯著差異，因此隧道周圍流場分析應考慮水力-力學耦合效應。另一方面網格局部加密下之計算結果相較於未加密之結果，能有效反應水力傳導係數驟降之影響。
關鍵詞：水力-力學雙向耦合、岩盤隧道、水力傳導係數、剪脹
;For radioactive waste disposal tunnels, the groundwater flow around the tunnel wall is an important issue for safety assessment. Previous study found that the distribution of discontinuous orientation and the anisotropy of stress can induce anisotropic hydraulic conductivity of rock masses. It is also found that the dilatancy in the mechanical behavior of fractures is not negligible for evaluating the groundwater flow around the tunnel. In this study, we will further investigate the influence of the hydro-mechanical coupling on the groundwater flow field around the tunnel. The JRC-JCS mode is used to calculate the behavior of the normal closure and the dilatancy of the fracture, and the spatial distribution of hydraulic conductivity around the tunnel is calculated by the Oda model. The finite difference method was used to caculate the flow field and pore water pressure around the tunnel. The density of the grids near the tunnel was increased. The effective stress field around the tunnel is calculated considering the pore water pressure, and iteratively calculates to converge to indicate the interaction between the flow field and the stress field. The model used in this study was established at a depth of 650 meters underground. Considering the different boundary stress and the anisotropy of the fracture distribution. The results show that the tunnel inflow of the two-way coupling method is about 20% higher than that of the one-way coupling method. Under different anisotropy parameters, the dilating area and the dilatancy contribution under the two-way coupling method are significantly different from the one-way coupling method. Therefore, the hydro-mechanical coupling effect should be considered in the flow field analysis around the tunnel. The calculation result under the increasing density of the grid can effectively reflect the influence of the sudden drop of the hydraulic conductivity compared with the result of the original grid size.
Keywords: Hydro-mechanical coupling, rock mass, tunnel, hydraulic conductivity, shear dilatancy
<br>運用數值計算進行楔形岩體破壞之敏感度分析;Sensitivity study of wedge failure by using numerical calculation
http://ir.lib.ncu.edu.tw/handle/987654321/81770
title: 運用數值計算進行楔形岩體破壞之敏感度分析;Sensitivity study of wedge failure by using numerical calculation abstract: 一般常見的岩坡類型可分為四種：(1)平面型，(2)楔型，(3)圓弧型及(4)傾覆型。台灣位處於造山帶，斷層、節理，等構造發達，這些構造在岩體之中相互交錯易形成楔形，因此楔形破壞在台灣須格外注意。針對楔形岩體的穩定性分析，一般採用剛塊法，其假設楔形體為剛體，不考慮岩體本身變形性，忽略不連續面上垂直於兩不連續面交線之剪力，但以真實情形來看，面對大型的楔形體時，由於岩體的裂隙多，變形性大，若使用剛塊法做分析顯然會有偏差。因此李錫堤(1989)提出最大剪力強度法，假設不連續面上垂直兩不連續面交線之剪力等於岩體不連續面之剪力強度提供的最大剪力來做分析。由於真實岩體的性質多介於剛體與變形體之間，前者常會過估不連續面上之正向力以獲得較高的安全係數，而後者則有低估兩個不連續面上之正向力以致獲得較低安全係數的情形。實際上此兩方法正好提供了楔形岩體安全係數的上下邊界。
本研究為瞭解真實岩體不連續面上真實剪力大小以求得正向力來求取安全係數，擬使用數值模擬軟體Flac2D(7.0)/Flac3D(5.0)分析在不連續面上凝聚力為零時楔形體在不同的不連續面交線傾沒角、不同的面角大小及不連續面上不同的摩擦角的情況下其真實剪力為何，以求得岩體滑動前之安全係數，並找出合適的評估方式。
研究結果顯示，不連續面摩擦角大於不連續面交線傾沒角時，Flac2D 與Flac3D 計算之安全係數皆在前人定義上下邊界內，且其接近最大剪力強度法之結果。Flac2D 與Flac3D 計算結果相似，故可以Flac2D 做分析較為快速。Flac3D 計算之安全係數時若不連續面交線傾沒角大於不連續面摩擦角時須使用強度折減法計算。
;Slope failure can be divided into four categories: (1) planer failure (2) wedge failure (3) circular failure (4) topple failure. Taiwan locates on Orogenic belts. There are a lot of geological structures, such as joint and faults. These structures cross each other and form rock wedge easily. In analysis of wedge stability, engineers use rigid block method commonly. The method assumed a wedge is a rigid body, and don’t consider deformability of the wedge. Therefore, shear force perpendicular to intersection line of the two discontinuities on the discontinuity plane can be neglected. However, when we are involving a large rock wedge, fractures and deformability can not be over looked. Lee (1989) proposes maximum shear strength method for a large rock wedge analysis. He assumed the shear force perpendicular to intersection line of the two discontinuities on the discontinuity is equal to the maximum shear force offering from shear strength of the discontinuity. In reality, the property of a rock wedge is between rigid body and deformable body. The former method would overestimate normal force which makes higher factor of safety, the latter would underestimate normal force which makes lower factor of safety. Thus the two methods, rigid wedge method and maximum shear strength method, provide the upper and lower boundary of factor of safety.
In this study, calculate the shear force of wedge to get factor of safety before wedge sliding. We use both Flac2D(7.0) and Flac3D(5.0) to compare which method is more suitable for calculating factor of safety in different cases by using different plunges of intersection line of two discontinuities, different dihedral angles and different friction angles of discontinuity.
The result of this study shows that if friction angle of discontinuity is larger than plunge of intersection line of two discontinuities, factor of safety calculated by Flac2D/Flac3D are between boundaries calculated by previous study and it is close to the result of maximum shear strength method. In addition, because the result of Flac2D and Flac3D is similar, Flac2D can be used for faster analysis When Flac3D is used, if friction angle of discontinuity is smaller than plunge of intersection line of two discontinuities, we should use shear strength reduction method to calculate factor of safety of the wedge.
<br>3D列印裂隙網絡試體於不同圍壓下裂隙力學與水力平均內寬之量測
http://ir.lib.ncu.edu.tw/handle/987654321/81768
title: 3D列印裂隙網絡試體於不同圍壓下裂隙力學與水力平均內寬之量測 abstract: 天然氣儲存、二氧化碳封存和核廢料處置，常選擇低滲透岩石作為主要的地質障壁，低滲透岩石因其結構緻密，孔隙體積較低，滲透率主要由裂隙所主導，然而現地岩體不連續面分布複雜，加上體積過大，不利於現地試驗直接量測流體在裂隙岩體中的流動方式與裂隙受力變形特徵之關係。近年來，3D列印技術逐漸成熟，以數位模型為基礎，透過光敏樹脂和石膏粉末，以堆疊累積的方式來建構3D岩石模型，且因容易修改模型、無須製作模具、成型速度快等優點，該技術已運用在探討岩石力學領域方面。本研究利用裂隙參數(裂隙中心位置、開口寬、裂隙半徑和位態)生成裂隙網絡，並使用光固化3D列印技術列印裂隙岩體圓柱型試體，並利用高圍壓孔隙體積/滲透率量測儀進行滲透率和孔隙體積量測，以探討裂隙網絡岩體在不同圍壓下的滲透率行為以及裂隙受力閉合特性，同時也利用理論計算的方式，計算相同裂隙網絡滲透率條件下之水力平均內寬，並與透過孔隙體積量測獲得之力學平均內寬進行比較。四個試體量測到的滲透率值介於1.73×10-12 m2 ~ 2.73×10-12 m2 (圍壓介於0.3MPa ~ 4MPa)，而孔隙體積介於715.92 mm3 ~ 1331.35 mm3 (圍壓介於1MPa ~ 4MPa)。計算得到的水力平均內寬介於37.25μm ~ 43.75μm (圍壓介於0.3MPa ~ 4MPa)，其對應力的敏感性較低；而計算得到的力學平均內寬介於86.73μm ~ 161.29μm (圍壓介於1MPa ~ 4MPa)，其對應力的敏感性較高。透過雙曲線和半對數曲線兩種不同內寬閉合模型進行擬合，發現兩種模型對於力學平均內寬閉合量擬合的相關係數介於0.91 ~ 0.99之間，能良好地描述力學平均內寬閉合量與有效應力之間的關係，而對於水力平均內寬閉合量擬合的相關係數則介於0.18 ~ 0.86之間，因水力平均內寬對有效應力的敏感性較差。力學平均內寬與水力平均內寬之比值介於2.13~4.21之間。;Low-permeability rocks are often used as the main geological barrier in natural gas storage, carbon dioxide storage and nuclear waste disposal. Low-permeability rock is dense in structure, low in pore volume, and permeability mainly dominated by its fractures. However, the overly large mass and the complex discontinuity make it unfavorable in the in-situ test which measures the relationship between flow pattern of fluid in fractured rock mass and deformation characteristics of fracture. In recent years, 3D printing technology has gradually matured. Using digital model as the foundation, 3D rock model is constructed by stacking and accumulating through photosensitive resin and gypsum powder. The technology has various advantages such as easy modification, requires no molds and fast forming and has been applied in rock mechanics fields for academic exploration. In order to investigate the permeability behavior of fractured network rock mass under different confining pressures and the closure characteristics of fractured forces, this study used the fracture parameters (fracture center position, aperture, fracture radius, and orientation) to generate a fracture network; the fractured rock mass cylindrical specimen was printed using photocuring 3D printing technology, and the permeability and pore volume measurement were performed using a high confining pressure pore volume/permeability instrument. At the same time, the theoretical calculation method is used to calculate the hydraulic average aperture under the same fracture network permeability. The hydraulic average aperture is then compared with mechanical average aperture, which is found via pore volume measurement. The permeability values measured by the four specimens ranged from 1.73×10-12 m2 to 2.73×10-12 m2 (confining pressure is between 0.3 MPa and 4 MPa), while the pore volume ranged from 715.92 mm3 to 1331.35 mm3. (confining pressure is between 1MPa and 4MPa). The calculated hydraulic average aperture is between 37.25μm and 43.75μm (confining pressure is between 0.3MPa and 4MPa), which is less sensitive to stress; the calculated mechanical average aperture is between 86.73μm and 161.29μm (confining pressure is between 1MPa and 4MPa), and its sensitivity to stress is high. Through the fitting of two different aperture closure models of hyperbolic and semi-logarithmic curves, it is found that the correlation coefficient between the two models of mechanical average aperture closure is between 0.91 and 0.99, which can well describe the relationship between the mechanical average aperture closure and the effective stress. The correlation coefficient for the fitting of the hydraulic average aperture closure is between 0.18 and 0.86, because the hydraulic average aperture is less sensitive to effective stress. The ratio between mechanical average aperture and hydraulic average aperture is between 2.13 and 4.21.
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