寨頭村黃土邊坡包氣帶水分運移規(guī)律研究
發(fā)布時間：2019-01-26 09:40
【摘要】：本文依托國家重點基礎(chǔ)研究發(fā)展計劃(973計劃)黃土重大災(zāi)害成災(zāi)機理及災(zāi)害鏈演化規(guī)律課題,通過室外滲水試驗和室內(nèi)滲透試驗及土壤水分特征曲線測定試驗,根據(jù)非飽和滲流理論,結(jié)合有限元軟件模擬室外滲水試驗及黃土邊坡包氣帶內(nèi)水分的運移變化,研究在不同外界因素影響下黃土包氣帶內(nèi)水分運移規(guī)律。室外滲水試驗場地位于陜西省寨頭村黃土邊坡。根據(jù)試驗觀測數(shù)據(jù),分析黃土包氣帶內(nèi)水分運移變化。黃土邊坡坡面上開挖探槽,深度為1m,并采用環(huán)刀進(jìn)行原位取樣。所取土樣進(jìn)行室內(nèi)滲透試驗和土壤水分特征曲線測定試驗,得到黃土飽和滲透系數(shù)和黃土土壤水分特征曲線。根據(jù)試驗結(jié)果,運用非飽和滲流理論,得到黃土飽和滲透系數(shù)與非飽和滲透系數(shù)之間的關(guān)系,為下一步數(shù)值模擬提供模型參數(shù)。運用非飽和滲流理論,對寨頭村黃土邊坡包氣帶進(jìn)行水文地質(zhì)條件概化,建立鉛直柱面二維非穩(wěn)定非飽和滲流數(shù)值模型,模擬滲水試驗過程中黃土包氣帶內(nèi)水分運移變化,并根據(jù)實際滲水試驗結(jié)果對模型進(jìn)行擬合,分析試驗過程中黃土包氣帶內(nèi)水分運移分布特征。根據(jù)試驗結(jié)果和模型運行結(jié)果,可知滲水試驗過程中黃土包氣帶淺層土壤含水率發(fā)生變化,且豎直方向變化范圍大于水平方向變化范圍,變化深度小于4m。黃土邊坡包氣帶水分運移受三種影響因素:降水條件、蒸發(fā)條件和黃土邊坡臨空面坡度條件。降水影響因素分為持續(xù)性小雨(降水時間為24h,降水強度為3mm/h)、短時暴雨(降水時間為2h,降水強度為36mm/h)和無降水;蒸發(fā)影響因素分為強蒸發(fā)(蒸發(fā)強度為0.5mm/h)和弱蒸發(fā)(蒸發(fā)強度為0.05mm/h);黃土邊坡臨空面坡比分為1:1、1:0.67和1:0.33。三種影響因素共同作用,共設(shè)計18種研究方案。根據(jù)非飽和滲流理論,將黃土邊坡包氣帶內(nèi)水分的運移概化為鉛直平面二維非穩(wěn)定非飽和滲流,結(jié)合有限元軟件建立相應(yīng)的數(shù)值模型。在不同研究方案下,模型運行結(jié)果進(jìn)行對比、分析,并根據(jù)模型結(jié)果研究黃土邊坡包氣帶內(nèi)水分運移變化規(guī)律。根據(jù)模型運行結(jié)果和分析,得到以下結(jié)論:1、本次室外滲水試驗黃土包氣帶土壤含水率變化影響范圍小于4m。2、黃土包氣帶深層土壤含水率無明顯變化,但仍然存在水分運移。3、持續(xù)性小雨(持續(xù)時間為24h,降水強度為3mm/h)與短時暴雨(持續(xù)時間為2h,降水強度為36mm/h)相比,持續(xù)性小雨更易于降水入滲。4、蒸發(fā)強度越大,黃土邊坡包氣帶土壤含水率影響變化深度越深,水分運移變化影響作用越明顯。5、黃土邊坡臨空面坡度緩,利于降水入滲補給和蒸發(fā)排泄,臨空面坡度陡,不利于降水入滲和蒸發(fā)排泄。
[Abstract]:In this paper, based on the National key basic Research and Development Program (973 Plan), the mechanism of major loess disasters and the evolution law of the disaster chain are discussed. Through the outdoor seepage test, the indoor permeation test and the soil moisture characteristic curve determination test, According to the theory of unsaturated seepage, combined with the finite element software to simulate the outdoor seepage test and the water migration change in the loess slope aeration zone, the water migration law in the loess aeration zone under the influence of different external factors is studied. Outdoor seepage test site is located in the Loess Slope of Zhai Tou Village, Shaanxi Province. Based on the experimental data, the water migration in loess aeration zone is analyzed. The depth of the trench on the slope of loess slope is 1 m, and the loop knife is used to sample in situ. The saturated permeability coefficient of loess and the characteristic curve of soil moisture of loess were obtained by indoor permeation test and soil moisture characteristic curve measurement. Based on the experimental results, the relationship between the saturated permeability coefficient and the unsaturated permeability coefficient of loess is obtained by using the unsaturated seepage theory, which provides the model parameters for further numerical simulation. By using unsaturated seepage theory, the hydrogeological conditions of unsaturated zone in loess slope of Zatoucun are generalized, and a two-dimensional unsaturated seepage numerical model of vertical column is established to simulate the change of water migration in loess aerated zone during seepage test. The model was fitted according to the actual seepage test results, and the characteristics of water migration and distribution in the loess aeration zone during the test were analyzed. According to the test results and model operation results, it can be seen that the moisture content of shallow soil in the loess aerated zone changes during the seepage test, and the variation range of vertical direction is larger than that of horizontal direction, and the depth of variation is less than 4 m. There are three influencing factors on water transport in aeration zone of loess slope: precipitation condition, evaporation condition and slope condition of loess slope. The influencing factors of precipitation are continuous light rain (precipitation time is 24 hours, precipitation intensity is 3mm/h), short term rainstorm (precipitation time is 2 hours, precipitation intensity is 36mm/h) and no precipitation. The factors affecting evaporation include strong evaporation (evaporation intensity is 0.5mm/h) and weak evaporation (evaporation intensity is 0.05mm/h), and the score of loess slope is 1: 1: 1: 0.67 and 1: 0.33 respectively. A total of 18 kinds of research schemes were designed by the interaction of three kinds of influencing factors. According to the theory of unsaturated seepage, the migration of moisture in the aerated zone of loess slope is generalized to two-dimensional unsaturated seepage in a vertical plane, and the corresponding numerical model is established with the finite element software. Under different research schemes, the results of model operation are compared and analyzed, and according to the model results, the variation of water migration in aeration zone of loess slope is studied. According to the results and analysis of the model, the following conclusions are obtained: 1, the influence range of soil moisture content in loess aeration zone is less than 4m.2, but there is no obvious change in deep soil moisture content in loess aeration zone. But there is still water migration. 3. Persistent light rain (duration is 24 hours, precipitation intensity is 3mm/h) and short term rainstorm (duration is 2 hours, precipitation intensity is 36mm/h), persistent light rain is easier to precipitation infiltration. The greater the evaporation intensity, the deeper the influence of soil moisture content in the aerated zone of loess slope is, and the more obvious the effect of water migration is. 5, the slope of loess slope is slow, which is conducive to precipitation infiltration, recharge and evaporation discharge, and the slope is steep. It is unfavorable to precipitation infiltration and evaporation and excretion.
【學(xué)位授予單位】：長安大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2015
【分類號】：P641.2
本文編號：2415361
[Abstract]:In this paper, based on the National key basic Research and Development Program (973 Plan), the mechanism of major loess disasters and the evolution law of the disaster chain are discussed. Through the outdoor seepage test, the indoor permeation test and the soil moisture characteristic curve determination test, According to the theory of unsaturated seepage, combined with the finite element software to simulate the outdoor seepage test and the water migration change in the loess slope aeration zone, the water migration law in the loess aeration zone under the influence of different external factors is studied. Outdoor seepage test site is located in the Loess Slope of Zhai Tou Village, Shaanxi Province. Based on the experimental data, the water migration in loess aeration zone is analyzed. The depth of the trench on the slope of loess slope is 1 m, and the loop knife is used to sample in situ. The saturated permeability coefficient of loess and the characteristic curve of soil moisture of loess were obtained by indoor permeation test and soil moisture characteristic curve measurement. Based on the experimental results, the relationship between the saturated permeability coefficient and the unsaturated permeability coefficient of loess is obtained by using the unsaturated seepage theory, which provides the model parameters for further numerical simulation. By using unsaturated seepage theory, the hydrogeological conditions of unsaturated zone in loess slope of Zatoucun are generalized, and a two-dimensional unsaturated seepage numerical model of vertical column is established to simulate the change of water migration in loess aerated zone during seepage test. The model was fitted according to the actual seepage test results, and the characteristics of water migration and distribution in the loess aeration zone during the test were analyzed. According to the test results and model operation results, it can be seen that the moisture content of shallow soil in the loess aerated zone changes during the seepage test, and the variation range of vertical direction is larger than that of horizontal direction, and the depth of variation is less than 4 m. There are three influencing factors on water transport in aeration zone of loess slope: precipitation condition, evaporation condition and slope condition of loess slope. The influencing factors of precipitation are continuous light rain (precipitation time is 24 hours, precipitation intensity is 3mm/h), short term rainstorm (precipitation time is 2 hours, precipitation intensity is 36mm/h) and no precipitation. The factors affecting evaporation include strong evaporation (evaporation intensity is 0.5mm/h) and weak evaporation (evaporation intensity is 0.05mm/h), and the score of loess slope is 1: 1: 1: 0.67 and 1: 0.33 respectively. A total of 18 kinds of research schemes were designed by the interaction of three kinds of influencing factors. According to the theory of unsaturated seepage, the migration of moisture in the aerated zone of loess slope is generalized to two-dimensional unsaturated seepage in a vertical plane, and the corresponding numerical model is established with the finite element software. Under different research schemes, the results of model operation are compared and analyzed, and according to the model results, the variation of water migration in aeration zone of loess slope is studied. According to the results and analysis of the model, the following conclusions are obtained: 1, the influence range of soil moisture content in loess aeration zone is less than 4m.2, but there is no obvious change in deep soil moisture content in loess aeration zone. But there is still water migration. 3. Persistent light rain (duration is 24 hours, precipitation intensity is 3mm/h) and short term rainstorm (duration is 2 hours, precipitation intensity is 36mm/h), persistent light rain is easier to precipitation infiltration. The greater the evaporation intensity, the deeper the influence of soil moisture content in the aerated zone of loess slope is, and the more obvious the effect of water migration is. 5, the slope of loess slope is slow, which is conducive to precipitation infiltration, recharge and evaporation discharge, and the slope is steep. It is unfavorable to precipitation infiltration and evaporation and excretion.
【學(xué)位授予單位】：長安大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2015
【分類號】：P641.2
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