流變特性對黃土邊坡穩(wěn)定性影響初探
發(fā)布時間：2018-11-13 12:38
【摘要】：我國中西部地區(qū)黃土分布廣泛且深厚,由于歷史上對黃土區(qū)森林的過度開發(fā)加上長期水土流失的作用,使得如今的中西部黃土區(qū)形成了大量的黃土邊坡,嚴重制約著西部地區(qū)基礎設施建設的發(fā)展。流變特性是黃土材料的主要力學特性之一。已有工程實例表明,自然界中許多的黃土邊坡在失穩(wěn)前都表現(xiàn)出了明顯的流變現(xiàn)象,即邊坡的失穩(wěn)與邊坡土體的流變性質(zhì)有關。因此,如何在邊坡穩(wěn)定性分析中考慮邊坡土體的流變性質(zhì)對邊坡工程的發(fā)展具有十分重要的意義。本文主要研究黃土流變特性對邊坡穩(wěn)定性的影響,同時將考慮黃土流變特性的邊坡穩(wěn)定性分析方法與傳統(tǒng)的理想彈塑性強度折減法和極限平衡法進行對比。通過分析三種方法計算出的邊坡潛在滑動面位置的不同、安全系數(shù)差異和邊坡位移的大小,得出三種方法的異同。通過對不同坡高和不同坡腳的邊坡模型進行計算分析,得出以下結論:(1)三種邊坡穩(wěn)定性分析方法計算出的滑面位置均是一條通過坡腳貫穿整個坡體的圓弧面,其中極限平衡法和理想彈塑性強度折減法計算出的滑面位置幾乎是相同的,流變強度折減法計算出的邊坡潛在滑動面在坡頂處更靠近邊坡臨空面,在滑面最低處更靠近模型底部。通過分析理想彈塑性強度折減法和流變強度折減法計算出的邊坡滑動帶可以發(fā)現(xiàn),使用流變強度折減法計算出的不同邊坡模型的潛在滑動帶始終處于理想彈塑性強度折減法計算出的邊坡潛在滑動帶內(nèi)部,說明流變強度折減法計算出的潛在滑動帶寬度小于理想彈塑性強度折減法計算出的邊坡潛在滑動帶寬度。(2)三種方法計算出的安全系數(shù)中,考慮流變的強度折減法計算出的安全系數(shù)最小,極限平衡法的計算所得安全系數(shù)最大,理想彈塑性強度折減法計算得出的邊坡安全系數(shù)大小處于兩者中間。極限平衡法與理想彈塑性強度折減法計算出的邊坡安全系數(shù)較為接近,相對差值約為1%-2%,流變強度折減法計算得出的安全系數(shù)與另外兩種方法計算所得安全系數(shù)差值較大,相對差值約為5%-11%,說明流變特性對邊坡穩(wěn)定性的影響較大。(3)考慮流變的強度折減法和理想彈塑性強度折減法計算出的邊坡位移中,在折減系數(shù)小于流變強度折減法計算出的安全系數(shù)時,流變強度折減法計算出的邊坡位移值較大,且二者邊坡位移差值穩(wěn)定,不隨折減系數(shù)的增加而變化。當折減系數(shù)大于安全系數(shù)時,流變強度折減法計算所得邊坡位移明顯大于理想彈塑性強度折減法計算所得邊坡位移,且二者差值隨著折減系數(shù)的增加逐漸增大。因此進行邊坡位移監(jiān)測的過程中,在設定邊坡位移預警值時應考慮邊坡土體的流變性質(zhì)。
[Abstract]:Loess is widely and deeply distributed in the central and western regions of China. Because of the overdevelopment of the forest in the loess region in history and the effect of long-term soil erosion, a large number of loess slopes have been formed in the loess region of the central and western regions today. It seriously restricts the development of infrastructure construction in the western region. Rheological property is one of the main mechanical properties of loess materials. Engineering examples have shown that many loess slopes in nature show obvious rheological phenomena before instability, that is, the slope instability is related to the rheological properties of slope soil. Therefore, how to consider the rheological properties of slope soil in slope stability analysis is of great significance to the development of slope engineering. In this paper, the influence of loess rheological characteristics on slope stability is mainly studied. At the same time, the slope stability analysis method considering loess rheological property is compared with the traditional ideal elastic-plastic strength reduction method and limit equilibrium method. By analyzing the difference of the potential sliding surface location, the safety factor and the displacement of the slope calculated by the three methods, the similarities and differences of the three methods are obtained. Through the calculation and analysis of the slope models with different slope heights and different slope feet, the following conclusions are drawn: (1) the position of the sliding surface calculated by the three slope stability analysis methods is a circular arc through the whole slope body through the foot of the slope. The position of the slip surface calculated by the limit equilibrium method and the ideal elastic-plastic strength reduction method is almost the same, and the potential sliding surface of the slope calculated by the rheological strength reduction method is closer to the empty surface of the slope at the top of the slope. It is closer to the bottom of the model at the lowest point of the sliding surface. By analyzing the slip zone calculated by the ideal elastic-plastic strength reduction method and rheological strength reduction method, it can be found that, The potential slip zone of different slope models calculated by rheological strength reduction method is always inside the slope potential slip zone calculated by ideal elastic-plastic strength reduction method. It shows that the width of potential slip band calculated by rheological strength reduction method is smaller than that calculated by ideal elastic-plastic strength reduction method. (2) among the safety factors calculated by the three methods, The safety factor calculated by the strength reduction method of rheology is the smallest, the safety factor by the limit equilibrium method is the largest, and the safety factor of the slope calculated by the ideal elastic-plastic strength reduction method is in the middle of the two. The limit equilibrium method is close to the slope safety factor calculated by the ideal elastic-plastic strength reduction method, and the relative difference is about 1-2. The difference between the safety coefficient calculated by the rheological strength reduction method and that obtained by the other two methods is quite large, and the relative difference is about 5- 11. It shows that the rheological characteristics have a great influence on the slope stability. (3) in the slope displacement calculated by the strength reduction method and the ideal elastic-plastic strength reduction method, when the reduction coefficient is less than the safety factor calculated by the rheological strength reduction method, The value of slope displacement calculated by rheological strength reduction method is large and the difference of slope displacement between them is stable and does not change with the increase of reduction coefficient. When the reduction coefficient is greater than the safety factor, the slope displacement calculated by rheological strength reduction method is obviously larger than that calculated by the ideal elastic-plastic strength reduction method, and the difference between the two values increases gradually with the increase of the reduction coefficient. Therefore, in the process of slope displacement monitoring, the rheological properties of slope soil should be considered when setting the early warning value of slope displacement.
【學位授予單位】：長安大學
【學位級別】：碩士
【學位授予年份】：2017
【分類號】：TU444
本文編號：2329129
[Abstract]:Loess is widely and deeply distributed in the central and western regions of China. Because of the overdevelopment of the forest in the loess region in history and the effect of long-term soil erosion, a large number of loess slopes have been formed in the loess region of the central and western regions today. It seriously restricts the development of infrastructure construction in the western region. Rheological property is one of the main mechanical properties of loess materials. Engineering examples have shown that many loess slopes in nature show obvious rheological phenomena before instability, that is, the slope instability is related to the rheological properties of slope soil. Therefore, how to consider the rheological properties of slope soil in slope stability analysis is of great significance to the development of slope engineering. In this paper, the influence of loess rheological characteristics on slope stability is mainly studied. At the same time, the slope stability analysis method considering loess rheological property is compared with the traditional ideal elastic-plastic strength reduction method and limit equilibrium method. By analyzing the difference of the potential sliding surface location, the safety factor and the displacement of the slope calculated by the three methods, the similarities and differences of the three methods are obtained. Through the calculation and analysis of the slope models with different slope heights and different slope feet, the following conclusions are drawn: (1) the position of the sliding surface calculated by the three slope stability analysis methods is a circular arc through the whole slope body through the foot of the slope. The position of the slip surface calculated by the limit equilibrium method and the ideal elastic-plastic strength reduction method is almost the same, and the potential sliding surface of the slope calculated by the rheological strength reduction method is closer to the empty surface of the slope at the top of the slope. It is closer to the bottom of the model at the lowest point of the sliding surface. By analyzing the slip zone calculated by the ideal elastic-plastic strength reduction method and rheological strength reduction method, it can be found that, The potential slip zone of different slope models calculated by rheological strength reduction method is always inside the slope potential slip zone calculated by ideal elastic-plastic strength reduction method. It shows that the width of potential slip band calculated by rheological strength reduction method is smaller than that calculated by ideal elastic-plastic strength reduction method. (2) among the safety factors calculated by the three methods, The safety factor calculated by the strength reduction method of rheology is the smallest, the safety factor by the limit equilibrium method is the largest, and the safety factor of the slope calculated by the ideal elastic-plastic strength reduction method is in the middle of the two. The limit equilibrium method is close to the slope safety factor calculated by the ideal elastic-plastic strength reduction method, and the relative difference is about 1-2. The difference between the safety coefficient calculated by the rheological strength reduction method and that obtained by the other two methods is quite large, and the relative difference is about 5- 11. It shows that the rheological characteristics have a great influence on the slope stability. (3) in the slope displacement calculated by the strength reduction method and the ideal elastic-plastic strength reduction method, when the reduction coefficient is less than the safety factor calculated by the rheological strength reduction method, The value of slope displacement calculated by rheological strength reduction method is large and the difference of slope displacement between them is stable and does not change with the increase of reduction coefficient. When the reduction coefficient is greater than the safety factor, the slope displacement calculated by rheological strength reduction method is obviously larger than that calculated by the ideal elastic-plastic strength reduction method, and the difference between the two values increases gradually with the increase of the reduction coefficient. Therefore, in the process of slope displacement monitoring, the rheological properties of slope soil should be considered when setting the early warning value of slope displacement.
【學位授予單位】：長安大學
【學位級別】：碩士
【學位授予年份】：2017
【分類號】：TU444
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