發(fā)布時(shí)間：2018-03-24 16:46

  本文選題：干濕循環(huán)　切入點(diǎn)：非飽和土　出處：《南昌航空大學(xué)》2017年碩士論文

【摘要】：土質(zhì)邊坡常常處于干濕循環(huán)的環(huán)境中,在每個(gè)循環(huán)過(guò)程中土體的性質(zhì)都在發(fā)生變化。目前對(duì)于干濕循環(huán)下土體性質(zhì)變化的研究主要集中于土體抗剪強(qiáng)度的衰減,而長(zhǎng)期處于干濕循環(huán)狀態(tài)下的土質(zhì)邊坡,其土體持水特性變化的累計(jì)效應(yīng)同樣是不可忽略的,將直接影響到邊坡的穩(wěn)定性,從而成為導(dǎo)致邊坡失穩(wěn)的主要原因之一。本文以砂土、粉土和粘土為研究對(duì)象,重點(diǎn)研究不同類型非飽和土的持水特性受干濕循環(huán)作用的影響規(guī)律。在此基礎(chǔ)上,采用數(shù)值計(jì)算的方法,首先研究干濕循環(huán)作用下,考慮非飽和土持水特性的變化與否對(duì)邊坡滲流和穩(wěn)定性的影響。其次,分析了干濕循環(huán)下不同土體飽和滲透系數(shù)、不同降雨條件和不同坡比條件對(duì)不同土質(zhì)邊坡的滲流場(chǎng)和穩(wěn)定性的影響。最后,對(duì)比不同土質(zhì)邊坡在土工膜覆蓋前后,其邊坡滲流和穩(wěn)定性的變化規(guī)律,探討土工膜覆蓋法加固邊坡的可行性和有效性。本文的主要研究成果如下:(1)干濕循環(huán)作用導(dǎo)致非飽和土的持水特性發(fā)生變化,具體表現(xiàn)為隨著干濕循環(huán)次數(shù)的增加,相同含水率條件下土體的基質(zhì)吸力變小,即土體的持水能力出現(xiàn)不可逆的衰減。其中,粘土的持水能力受干濕循環(huán)的影響最小、粉土次之,砂土最大。隨著干濕循環(huán)次數(shù)的增加,單次干濕循環(huán)對(duì)土體持水能力的衰減作用減弱。(2)干濕循環(huán)下,非飽和土持水特性的變化在一定程度上影響了邊坡土體含水率的分布和邊坡穩(wěn)定性的變化。其中,雨強(qiáng)較大時(shí),土體持水能力的衰減對(duì)粉土邊坡的滲流和穩(wěn)定性的影響較大;雨強(qiáng)較小時(shí),土體持水能力的衰減對(duì)粘土邊坡的滲流和穩(wěn)定性的影響較大。(3)干濕循環(huán)下,土體飽和滲透系數(shù)大小和不同降雨條件對(duì)不同土質(zhì)邊坡的滲流和穩(wěn)定性的影響程度主要取決于大氣降雨強(qiáng)度和土體滲透系數(shù)之間的相對(duì)大小關(guān)系。坡度較緩的邊坡穩(wěn)定性較好。(4)土工膜覆蓋法對(duì)粘土邊坡的防護(hù)效果好于粉土邊坡。對(duì)于粉土和粘土邊坡,分別以膜覆蓋邊界水平向里約為3m和1m處開始,膜下土體基本不受大氣降雨和蒸發(fā)的干擾。土工膜不同鋪設(shè)方式的護(hù)坡效果對(duì)比:對(duì)于粉土邊坡,土工膜直線形鋪設(shè)的效果好于階梯形,土工膜包邊長(zhǎng)度越短效果越好;而粘土邊坡的規(guī)律正好相反。
[Abstract]:Soil slope is often in the environment of dry and wet circulation, and the properties of soil are changing during each cycle. At present, the research of soil property change under dry and wet circulation is mainly focused on the attenuation of soil shear strength. However, the accumulative effect of the change of soil water holding property is also not negligible when the soil slope is in dry and wet cycle for a long time, which will directly affect the stability of the slope. Therefore, it becomes one of the main causes of slope instability. In this paper, the effects of dry and wet cycles on the water holding capacity of different types of unsaturated soils are mainly studied with sand, silt and clay as the research objects. In this paper, the numerical method is used to study the influence of the variation of unsaturated soil water holding property on the slope seepage and stability under dry and wet cycles. Secondly, the saturated permeability coefficient of different soils under dry and wet circulation is analyzed. The influence of different rainfall conditions and slope ratio conditions on the seepage field and stability of different soil slopes. Finally, the variation of seepage and stability of different soil slopes before and after geomembrane covering is compared. This paper discusses the feasibility and effectiveness of geomembrane covering method for slope reinforcement. The main research results in this paper are as follows: 1) the dry and wet cycle results in the change of water holding capacity of unsaturated soil, which is manifested by the increase of dry and wet cycles. Under the condition of the same moisture content, the soil matrix suction becomes smaller, that is, the water holding capacity of the soil is irreversibly attenuated, among which, the water holding capacity of clay is the least affected by dry and wet cycle, and that of silt is the second. With the increase of dry and wet cycle times, the attenuation effect of single dry and wet cycle on the water holding capacity of soil is weakened. The variation of water holding capacity of unsaturated soil influences the distribution of soil moisture content and the stability of slope to some extent, and the attenuation of soil water holding capacity has a great influence on the seepage and stability of silt slope when the rainfall intensity is high. When the rain intensity is small, the attenuation of soil water holding capacity has a great influence on the seepage and stability of clay slope. The influence of soil saturation permeability coefficient and different rainfall conditions on the seepage and stability of different soil slopes depends mainly on the relative relationship between the atmospheric rainfall intensity and the soil permeability coefficient. The stability of slope is better than that of silt slope. For silt and clay slope, the effect of geomembrane covering method is better than that of silt slope. The horizontal direction of the film cover boundary is about 3m and 1m, respectively, and the soil under the film is not disturbed by atmospheric rain and evaporation. The slope protection effects of different laying methods of geomembrane are compared: for silt slope, The effect of geotextile linear laying is better than that of step, and the shorter the envelope length of geomembrane is, the better the effect is, but the law of clay slope is just the opposite.
【學(xué)位授予單位】：南昌航空大學(xué)
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2017
【分類號(hào)】：TU43

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