風化弱軟化岩石引致邊坡失穩案例探討－以水璉礫岩邊坡為例

自然界中風化作用為造成岩石弱軟化的主因，強烈影響岩體工程之設計、施工以及其安定性。惟風化程度對岩石弱軟化之關係以至於其對邊坡穩定之影響，迄今仍缺乏一套系統性的量化評估方法。本研究以台灣東部海岸山脈水璉礫岩某一邊坡失穩案例為對象，探討邊坡岩石受風化作用後弱軟化的現象與微觀組構因子的變化，以及其引致邊坡穩定程度的下降。研究過程針對水璉礫岩進行不同次數的乾濕循環人工風化作用，探求不同風化程度消散耐久指數、單軸壓縮強度、點荷重強度以及視摩擦角的變化，結果顯示水璉礫岩風化後，抗風化能力下降、強度降低、變形性增加，且強度降低主要受到視凝聚力下降的影響，視摩擦角在人工風化過程的變化較不明顯；繼而採用個別元素法探討影響岩石弱軟化的敏感微觀因子，獲知透過數值方法考量試驗所得基質弱軟化的現象，可有效模擬不同風化程度岩石的應力－應變曲線；最後結合有限差分法數值分析，可探討風化引致岩石弱軟化對邊坡穩定的影響。

關鍵字

風化；水璉礫岩；數值分析；邊坡失穩

並列摘要

In nature, weathering made rocks to have a lower strength and greater deformation. Therefore, it is an important factor which needs to be considered for designing a safe engineering structure. However, there is no systematic study has been done for measuring the influence of the degree of weathering on the structures stability. In this study, the primary focus has been put on one of the Suilien Conglomerate slope in the Coastal Range of eastern Taiwan. This article investigates the variation of the mechanical and the microscopic properties after the weathering process on the conglomerate. The effect of these parameters on slope stability was discussed. By using artificial weathering circulations test on rapidly changing environmental moistures to found out the rock slake-durability index, uniaxial compressive strength, point load strength and apparent friction angle on different weathering degree. Testing results shows that the strength, slake-durability index of conglomerate decreases with the increase of the number with weathering cycles. The strength has been lower because of the decrease of visual cohesion, and the variation of apparent frictional deformation was not significant with the increase of circulating numbers. After artificial weathering, we use Discrete Element Method (DEM) to simulating the stress-strain curves obtained from uniaxial compressive tests, found out that the weakening and softening of rock are dominated by sensitive micro-parameters. Accordingly, this outcome is also adopted and taken into account in the slope stability analysis with finite different method. Thus the influence of the degree of weathering on slope stability can then be estimated and elucidated.

並列關鍵字

weathering ； conglomerate ； numerical analysis ； slope instability

主題瀏覽