夾層泥縫對邊坡破壞面發展行為之影響研究

The effect of clay seam on the failure surface development of rock slope

楊智凱(Chih-Kai Yang)

指導教授 ： 楊長義

淡江大學/工學院/土木工程學系碩士班/碩士(2015年)

https://doi.org/10.6846/TKU.2015.00805

摘要

近年來順向坡滑動常常造成重大災損，且其地質條件多為沿頁岩發展出破壞面。透過邊坡反算可反推出當邊坡產生滑動時，當時滑動面所提供之剪力強度，但反推分析所得之弱面剪力強度，不同於試驗室所得之弱面剪力強度。順向坡的特性是具順層的結構、且因受到層間之錯動(bedding shear)常存在層間摩擦剪動的泥層(clay layer)或稱泥縫(seam)。本研究將對泥縫、破壞面之漸進發展過程，探討邊坡含有夾泥之破壞行為，期望能對低傾角之順向坡滑動破壞，及試驗數據與現地反算不一致之矛盾現象獲得更佳的詮釋，並針對國道三號汐止順向坡滑動破壞之地質災害案例進行滑動破壞影響因素之探討。
本研究使用數值分析方式，探討邊坡含有夾層泥縫之破壞面發展行為，利用數值分析程式FLAC進行分析，探討泥縫幾何特性與剪力強度參數之敏感度，並採用重力增加法觀察破壞面發展行為。
研究結果得到主要結論：(1)以另類地質觀點，探討夾層泥縫對邊坡破壞面發展行為的影響，層間摩擦剪動的泥層與易泡水軟化的頁岩層是影響整體邊坡穩定的控制因素。(2)FLAC程式透過GIM法進行分析，針對材料之重力值進行逐步改變，就能快速的觀察邊坡破壞面發展的行為。(3)邊坡夾泥之幾何特性會影響整體邊坡穩定與破壞面位置的發展，邊坡坡壞面滑出位置隨著泥縫位置而改變，且在夾泥出露端於坡趾時最危險；邊坡有夾泥存在時，對整體邊坡穩定會有急劇的影響，但夾泥厚度對邊坡位置與安全係數沒有太大的影響。；夾泥傾角之改變，僅會影響邊坡滑動面位置的發展，對邊坡穩定影響不大。(4)邊坡夾泥材料之剪力強度參數會影響整體邊坡穩定與破壞面位置的發展，C/R值較高時(夾泥強度較貼近圍岩強度)，破壞面會趨於較淺層的圓弧型破壞，當C/R值較低時(夾泥強度較圍岩軟弱)，破壞面會趨於較深層的平面型破壞；邊坡對夾泥弱化摩擦角之弱化改變比凝聚力弱化改變敏感。(5)以國三地滑案例進行分析，分析結果與現地災變情形雷同，以FLAC程式GIM法進行分析，透過逐步增加重力g值可觀察到邊坡破壞面的發展與滑動塊體的形成。

關鍵字

順向坡 ； FLAC ； 破壞面發展 ； 重力增加法

並列摘要

In recent years, dip slope often create major damage and failure surface always development along shale. When slope slide, we can estimate landslide's shear strength by back calculation. But back calculation of the shear strength different from lab test of the shear strength. Dip slope have bedding structures, then layers always have clay layer or seam by bedding shear. In this study, we against clay seam and failure surface development, research the effect of clay seam on the failure surface development of rock slope. Hoping to find better interpretation of back calculation of the shear strength different from lab test of the shear strength. And research slope failure factors at 3.1K of the Third Freeway in Taiwan.

In this study, we research the effect of clay seam on the failure surface development of rock slope through numerical analysis. Research the effect of clay seam on the geometric properties and shear strength, then use gravity increase method to observed failure surface development.

The following conclusions are drawn：(1)Pointed out in different geological to investigate the effect of clay seam on the failure surface development of rock slope. Clay seam by bedding shear and shale soften by water is more important on slope stability. (2)Use gravity increase method by FLAC gradually change acceleration of gravity of material, can quick observation the failure surface development of rock slope. (3)Clay seam on the geometric properties can influences slope stability and failure surface development. Failure surface slide position will change by clay seam position. When clay seam on slope toe will be most danger. Slop have clay seam will influence slope stability, but change thickness of clay seam will not influence slope stability. Change dip of clay seam will influence failure surface development, but not influence slope stability. (4)Change shear strength of clay seam will influence slope stability and failure surface development. When C/R ratio is higher, failure surface will be more shallow and circular failure. When C/R ratio is lower, failure surface will be more deep and planar failure. Soften friction angle on clay seam will more sensitive than soften the cohesion on clay seam. (5)Research slope failure factors at 3.1K of the Third Freeway in Taiwan. Analysis results are now similar to actual place. Use gravity increase method by FLAC can observed the failure surface development.

並列關鍵字

dip slope ； FLAC ； failure surface development ； gravity increase method

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