結合井測及岩體評分探討廬山溫泉北坡斜坡深層重力變形的演育

Characterizing the deformation behavior of deep-seated gravitational slope deformation through integration of borehole exploration and surface investigation

林錫宏(Hsi-hung Lin)

指導教授 ： 林銘郎

國立臺灣大學/工學院/土木工程學研究所/博士(2020年)

https://doi.org/10.6342/NTU202003791

摘要

南投廬山溫泉北坡具有長期的岩體滑動現象，並對聚落安全及公路等造成威脅。然而，目前重力變形方向朝南，與劈理傾向（朝東或東南傾斜）並不一致，幾乎呈垂直正交，與既有斜坡深層重力變形研究案例的變形行為均不同。因此，廬山溫泉北坡具有獨特的地質條件，可能反映特別的地質模式。本研究利用地質及地中調查資料，建立地質模式，建立斜坡深層重力變形的地工特性評估方法，期能瞭解由斜坡深層重力變形的演育階段特徵與地質模式，並能做為應用於板岩區斜坡深層重力變形的評估方法。
本研究應用A21-1井的P波波速(Vp)量測成果，檢討與岩芯Q-logging後每米的log Qc值的關係，發現大致具有Vp = 0.6 x Log Qc + 4.0的關係。與Barton (1995)的關係式，可見廬山地區板岩P波波速Vp及log Qc關係式，顯著的向左偏移，推測係因廬山地區板岩岩石強度較低、劈理較為發達所致。
綜合劈理的傾角及分布深度，並參考各鑽井經Q-logging後的log Q值，區分為5種地質幾何樣式(Style)及地工分區的特徵岩體，反映岩體滑動的發展程度。 從廬山溫泉北坡研究成果顯示，各地質幾何樣式的平均Q值，大致為style A > style B > style C > style D > style E，這也反映由斜坡深層變形到沿特定滑動面的岩體滑動的發展歷程，並能應用在板岩區其他斜坡深層重力變形的場址調查。
廬山溫泉北坡的演化過程，推測為：(1)由東向西流的塔羅灣溪，侵蝕東側的變質砂岩層後，開始產生大規模、深層的岩體變形，位移方向朝東；(2)發生大規模、深層的岩體滑動，滑動方向朝東，岩體滑動的北側邊界，可能為J1節理，岩體滑動深入岩盤，以塊體運動的方式，劈理呈現水平的岩體，於趾部上方剪出滑動面之下的岩體被推擠，呈現撓曲傾翻狀；(3)東側的變質砂岩層，暫時阻止岩體繼續朝東滑變形；(4)但塔羅灣溪持續下切，尤其是馬海濮溪侵蝕LSN的坡趾，因此岩體變形方向轉為朝南。

關鍵字

斜坡深層重力變形 ； Q-logging 岩體評分 ； 地質樣式與地工分區 ； 變形行為 ； 重力變形演育

並列摘要

The northern slope in Lushan (NSL) in central Taiwan is recognized as a large deep-seated gravitational slope deformation (DSGSD) in anisotropic slate and is often activated by typhoons and heavy rainfall. However, a recent southward movement of the DSGSD was apparently not caused by translational sliding along the eastward-dipping cleavage in the NSL. Because the regional attitudes of the cleavages in the NSL moderately vary and no major fault has been observed in the field, the deformed cleavages with their random dips indicate that the deformation of the rockmass was caused by older mass movements. In addition, ancient progressive erosion of the NSL toe by the Talowan River, which passes through the eastern side of the slope, induced deep, large-scale mass movement toward the east. Based on detailed core recognition measurements including the cleavage dips, log Q values, and inclinometer measurements, this study identified five geometrical styles and geotechnical zones of the deformed rockmasses for characterization of the evolution of the NSL DSGSD with regard to the spatial distributions of old mass movements and recent transformations. Curves obtained from recent inclinometer measurements suggested two deformation behaviors, namely, specific sliding and progressive deformation. The underlying rockmass with overturned and flexural folding in cleavages at the slope toe have baffled a recent southward advancement of the DSGSD. Consequently, the deep specific sliding surface close to the basal disintegrated rockmass at the center of the NSL was transformed into progressive deformation, which mostly occurred in the overturned rockmass at the toe. Based on our observations, this study proposes the following relationship between the P-wave velocity (Vp, km/s) and log Qc (where Qc is a normalized Q) as an empirical model for slate in Taiwan: Vp = 0.6 × log Qc + 4.0. This empirical model might be suitable for the low-uniaxial compressive strength slate in the Lushan area and could be used for the quantitative evaluation of the geotechnical zone of the DSGSD of the NSL.

並列關鍵字

Deep-seated gravitational slope deformation ； Q-logging ； Geometrical style and geotechnical zones ； Deformation behaviors ； Progressive evolution

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