Geological Structure Study and the Impacts of the Erosion of the area along the New Central Cross-Island Highway in Yushan National Park
中文摘要
本研究之主要目的希望經由航空照片之地質判釋，野外實地之調查，並配合室內砂岩樣品之單軸抗壓強度之量測，了解玉山國家公園新中橫地區地質構造之特性，同時配合對研究區域內崩塌地之調查，討論研究區內尤其是新中橫公路沿線崩塌災害與地質構造及岩性間之關係。
研究區域內主要的地質構造包括和社背斜、同富山向斜、塔塔加斷層、隆華斷層與神木斷層。和社背斜與同富山向斜是影響全區的主要地質構造，它們同時為具有走向滑移特性之隆華斷層及神木斷層所截切。隆華斷層為左移斷層，神木斷層右移斷層，此二斷層呈共軛分佈，反應來自西北西-東南東之水平擠壓應力。除此之外，為數甚多之小規模褶皺分佈於以砂頁岩薄互層或厚頁岩夾薄層砂岩之下部南莊層及南港層(即本研究之構造地層單位B)中，而在上部南莊層及南港層(構造地層單位A)中則有甚為發達的破裂面存在。
研究區域內之新中橫公路沿線之崩塌現象極為普遍，崩塌的型式與規模均深受岩性與地質構造的影響。在關刀山砂岩與上部南莊層出露之地區，砂岩強度較強，岩體中之破裂面較為發達，而落石是邊坡最主要的破壞現象。在南港層與下部南莊層出露之區，頁岩所佔比例較高，砂岩層之厚度變薄，土石流、圓弧形破壞及平面型滑動是最常見之邊坡破壞型式。而就崩塌災害之規模而言，在主斷層帶及主要褶皺之軸部位置常有較大規模之破壞發生。
英文摘要
The main goal of this study was to make geographical determinations from aerial photographs, conduct field surveys, and measure the uniaxial compressive strength of sand stones in laboratory in order to understand the characteristics of the geological structure of the area along the New Central Cross-Island Highway in Yushan National Park. At the same time, a survey of the slump sites was conducted in order to discuss the relationship between slumps, geological structures, and geological characteristics in the study area, especially the area along the New Central Cross-Island Highway. The main geological structures in the study area included the Heshe anticline, Tongfushan syncline, Tataka fault, Longhua fault, and Shenmu fault. The Heshe anticline and Tongfushan syncline were the most influential geological structure in the area, which were intersected by the shifting Longhua fault and Shenmu fault. The Longhua fault is a left lateral fault, whereas the Shenmu fault is a right lateral fault. The two faults are a kind of conjugated distribution and are subjected to the west northwest and east southeast horizontal compression. Apart from this, there were a number of small-scale folds distributed in the thinly embedded sand shale layers and thick shale embedded in thin layers of sand stone in the lower part of the Nanjong and Nangang terranes (both classified as structural stratigraphic unit B in this study). In the upper part of the terranes(structural stratigraphic unit A), there were large ruptures. Slumps are a common phenomenon along the study area on the New Cross-Island Highway. The types and scales of the slumps are heavily influenced by geological characteristics and structures. The ruptures in the sand stones in Guandaoshan and the revealed upper Nanjong terrane were larger, and rockfalls was the major destructive force on the slopes. Shale made up a larger proportion in the Nangang and revealed lower part of Nanjong terrane, and the sand stone layer became thinner in these formations. Collapsed land, circular failure, and translational slides were the most common types of destructive forces. Larger scale of slumps occurred in the major fault zone and fold axis.
