海岸山脈邊坡穩定特性之探討－以水璉礫岩邊坡為例

Elucidating the Slope Stability of the Coastal Range Focusing on Suilien Conglomerate Slope

詹佩臻(Pei-Chen Chan)

指導教授 ： 翁祖炘 ； 王泰典

國立臺北科技大學/工程學院/資源工程研究所/碩士(2009年)

https://doi.org/10.6841/NTUT.2009.00640

摘要

自然界中風化作用為造成岩石弱軟化的主因，強烈影響岩體工程設計及其安定性，惟風化程度對岩石弱軟化之相互關係，迄今仍缺乏一套系統性的量化研究。
本研究以海岸山脈八里灣層內水璉礫岩為對象，探討水璉礫岩邊坡的地形特性與影響因子，透過極限平衡觀念，針對一邊坡失穩案例進行反算分析，探求水璉礫岩邊坡的力學特性參數。繼而設計一系列水璉礫岩試驗歷經人工風化環境，透過人工冷熱、乾濕與酸環境不同程度的循環條件，模擬自然風化過程物理崩解作用與化學分解作用，並進行多項力學試驗與岩象觀察，以探求風化作用對水璉礫岩力學特性與微觀組構的影響。進一步應用顆粒力學離散元素法瞭解礫岩風化過程不同微觀因子對其中視尺度力學特性的影響程度，繼而應用連體力學有限差分法建立宏觀尺度的邊坡穩定分析模型，利用中視尺度求得的力學特性參數，模擬分析邊坡的穩定特性，以利探討風化作用弱軟化礫岩對邊坡穩定的影響。
結果顯示風化弱軟化為影響水璉礫岩邊坡穩定的重要因子；且水璉礫岩因成岩過程複雜且壓埋時間不足，力學特性有些許的變異性，其隨風化循環次數的增加，單軸壓縮強度明顯弱化；抗風化能力有下降趨勢；而視摩擦特性具有異向性，且隨不同環境下風化程度增加其變異性各有不同發展；岩象觀察顯示風化過程中石英因岩屑類基質弱化而失去支撐，導致應力無法有效傳遞，研判為強度弱化原因之一。利用數值模擬單壓試驗，探討可能的風化作用影響參數為摩擦係數、基質楊氏模數、基質強度與膠結強度，推估邊坡失穩受基質及膠結強度控制；邊坡穩定分析顯示，參數持續弱化降低邊坡穩定性。

關鍵字

邊坡穩定 ； 水璉礫岩 ； 風化 ； 力學特性參數 ； 岩象

並列摘要

In nature, weathering causes rocks to have a lower strength and hence greater deformation. It is, therefore, an important factor which needs to be considered for designing safe engineering structures. However, no systematic study has been done for measuring the influence of the degree of weathering on the stability of structures.
In this study, the primary focus has been on the Suilien Conglomerate Slope of the Paliwan Formation in the Taiwan Coastal Range. Using the limit equivalent method for back analysis, the mechanical parameters of the slope were found. The effect of these parameters on the terrain properties was discussed.
This article investigates the variation of the mechanical and the mineralogical properties under the weathering process produced by means of artificial circulations on rapidly changing environmental conditions like temperature, moisture and acidity. The effect of weathering on the mechanical characteristics and on the microscopic texture of the Suilien Conglomerate was hence found.The variation of mechanical and mineralogical properties of Suilien Conglomerate during artificial weathering process was thus investigated. The mechanical parameters of the rock sample were obtained from Rock Mechanics Laboratory tests and at the microscopic level it was calculated using the Discrete Element Method (DEM) and both were compared to each other.
A comparison was also made between the macro parameters (mechanical parameters obtained from the Slope Stability) and the parameters obtained from the Rock Mechanics Laboratory tests. This comparison was made using the Finite Element Method (FEM). Using the above two comparisons, a relationship was developed between the degree of weathering and the Factor of Safety of the slope. The diagenesis time of the rock was short and therefore the cementation between its grains was weak. This weak cementation was a major cause for the variation of its mechanical properties. Testing results show that the strength, slaking and the durability index of conglomerate decrease with the increase in the number of cycles, and the variation of apparent frictional properties, with obvious anisotropy, is highly influenced by the decomposition or dissolution weathering mechanism. Since the matrix is weakened by the weathering process, it cannot hold the quartz grain. This leads to its loss as confirmed by the study of its mineralogical properties.
And using DEM to simulate UCS, we find that the following parameters are affected by the degree of weathering: matrix strength, cement strength, matrix Young’s modulus and friction. The factor of safety is controlled by the matrix strength and the cement strength. Lower these parameters; less is the factor of safety.

並列關鍵字

Landslide ； Suilien Conglomerate ； weathering ； mechanical parameters ； mineralogical properties

參考文獻

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