本文選題：黃土邊坡 + 降雨條件　； 參考：《蘭州交通大學(xué)》2017年碩士論文

【摘要】：降雨是引起各種地質(zhì)災(zāi)害的重要因素之一,尤其是黃土塬、梁、峁等地形發(fā)育完全的黃土地區(qū),為黃土邊坡的地質(zhì)災(zāi)害提供了天然條件。通過建立室內(nèi)邊坡模型,控制雨強(qiáng)、作用時間、邊坡坡腳等研究降雨引起的黃土邊坡失穩(wěn)過程,并利用土壓力盒、水分及孔隙水壓力傳感器等監(jiān)測土體內(nèi)部各項(xiàng)參數(shù)的變化,結(jié)合降雨過程和邊坡破壞發(fā)展過程進(jìn)行了針對性的分析。同時,運(yùn)用數(shù)值分析軟件建立與室內(nèi)模型試驗(yàn)同尺寸的數(shù)值模型,分析孔隙水壓力、滲流方向、抗剪強(qiáng)度等隨降雨的變化。主要研究內(nèi)容或成果如下:(1)浸潤線發(fā)展規(guī)律:相同邊界條件下,40°與55°邊坡模型的浸潤線推移規(guī)律保持一致:降雨前期,邊坡各處浸潤線向土體推移速率基本保持一直,為0.11m/hr;隨降雨邊坡表面土體飽和,坡腳處產(chǎn)生積水,坡頂、坡面的浸潤線推移速率下降,且坡面下降的更為嚴(yán)重,而在坡腳處的浸潤線推移速率受積水影響大于坡頂及坡面處的;40°邊坡模型的浸潤線推移速率較55°邊坡模型的快;同時,數(shù)值計算模型得出飽和-非飽和區(qū)域分界線對下方土體影響深度約5cm,且不隨外界條件變化;坡面處的雨水入滲方向隨降雨與坡面夾角不斷減小,甚至保持平行。(2)室內(nèi)模型監(jiān)測數(shù)據(jù)變化特性:通過對兩個模型試驗(yàn)土體內(nèi)部埋設(shè)監(jiān)測元件,再結(jié)合邊坡破壞發(fā)展過程,著重分析了不同點(diǎn)含水量、應(yīng)力與孔隙水壓力隨降雨時間的變化特征。(3)黃土邊坡的失穩(wěn)過程:降雨入滲→上部土體容重和水壓增加→裂縫產(chǎn)生、發(fā)展→坡腳軟化坍塌和土體內(nèi)部孔隙緩慢貫通并不斷擴(kuò)大→形成上下貫通的通道→邊坡體下滑力增加及抗剪強(qiáng)度降低→沿孔隙貫通的通道形成軟弱層→產(chǎn)生破壞。并針對邊坡破壞形態(tài)得出其對應(yīng)的破壞模式:40°和55°邊坡模型都屬于由坡腳軟化坍塌引起的牽引式破壞。(4)在一定循環(huán)間歇降雨雨強(qiáng)下,邊坡的安全系數(shù)與降雨時間有著直接的關(guān)系,邊坡的安全系數(shù)隨著降雨時間的增長而降低。穩(wěn)定系數(shù)減小的速率存在明顯的分界點(diǎn):降雨初期,安全系數(shù)減小的速率相對較大,隨著降雨時間的持續(xù),當(dāng)達(dá)到某時刻時,此時的最危險滑動面完全處于飽和區(qū),且在隨后的時間段內(nèi),時刻變化的最危險滑動面也完全處于飽和區(qū)時,邊坡穩(wěn)定系數(shù)依然有下降的趨勢,但相對平緩。
[Abstract]:Rainfall is one of the important factors that cause various geological disasters, especially in loess areas with well-developed terrain, such as loess plateau, beam and knoll, which provides natural conditions for geological disasters of loess slope.Through establishing indoor slope model, controlling rain intensity, acting time, slope foot and so on, the process of loess slope instability caused by rainfall is studied, and soil pressure box, moisture and pore water pressure sensor are used to monitor the change of soil mass internal parameters.Combined with rainfall process and slope failure development process, targeted analysis was carried out.At the same time, the numerical model with the same size as the indoor model test is established by using the numerical analysis software to analyze the variation of pore water pressure, seepage direction and shear strength with rainfall.The main research contents or results are as follows: (1) the law of the development of the infiltrating line: under the same boundary conditions, the infiltration line of 40 擄slope and 55 擄slope model is the same, and the moving rate of the infiltration line from the different parts of the slope to the soil is basically maintained at the beginning of the rainfall period.When the surface of the slope is saturated with rainfall, there is water at the bottom of the slope, and the velocity of the infiltration line of the top and slope decreases, and the slope decreases more seriously.However, at the foot of the slope, the velocity of the infiltration line is faster than that of the model of 40 擄slope at the top of the slope and the slope at the slope surface, and the velocity of the infiltration line is faster than that of the model of 55 擄slope at the foot of the slope, and at the same time,The numerical model shows that the depth of the boundary between saturated and unsaturated region is about 5 cm, and the depth of the boundary does not change with the external conditions, and the infiltration direction of Rain Water on the slope decreases with the angle between the rainfall and the slope.Even maintain parallelism. 2) change characteristics of indoor model monitoring data: by installing monitoring elements inside the soil mass of two model tests and combining with slope failure development process, the water content of different points is analyzed emphatically.The change of stress and pore water pressure with rainfall time) the unstable process of loess slope: the increase of bulk density and water pressure of the upper soil mass and the formation of cracks in the upper part of the loess slope by rainfall infiltration.The soft collapse at the foot of the slope and the gradual penetration and expansion of the internal pores of the soil to form a channel through which the downward force increases and the shear strength decreases and the weak layer is formed along the channel through which the pores are perforated will be destroyed.According to the failure pattern of slope, the corresponding failure modes: 40 擄and 55 擄are both tractive failure caused by slope foot softening and collapse.The safety factor of slope is directly related to rainfall time, and the safety factor of slope decreases with the increase of rainfall time.At the beginning of rainfall, the rate of safety factor decreases is relatively large. With the duration of rainfall, the most dangerous slip surface is completely in the saturation zone when the rainfall time is reached.And in the following time period, when the most dangerous sliding surface is in the saturation zone, the slope stability coefficient is still decreasing, but relatively flat.
【學(xué)位授予單位】：蘭州交通大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2017
【分類號】：TU411

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