非飽和黃土結合水特性及水分遷移問題研究
發(fā)布時間：2019-04-24 13:47
【摘要】：非飽和黃土遍布黃土高原,其水分狀態(tài)對其工程性質(zhì)有顯著影響,目前對其水分狀態(tài)尤其是結合水狀態(tài)的研究尚欠缺。論文通過等溫吸附法和熱重分析法確定了黃土中強結合水和弱結合水的含量,試驗結果表明黃土中結合水的含量主要與粘土礦物的含量有關,并且隨著粘土礦物含量的增加而增加,建立了不同類型結合水含量與粘土礦物含量之間的關系式,并通過試驗和理論分析相結合的方法確定了不同類型的結合水的密度和水膜厚度。吸力是影響非飽和土滲流問題的重要變量,不同含水量水平的土體可存在不同吸力類型,其對滲流問題有不同影響,目前針對非飽和土滲流問題尚缺乏對吸力的分類的研究。為此,在分析孔隙水賦存狀態(tài)及及其吸力作用的基礎上,將非飽和土中孔隙水分為結合水、毛細角邊水和連通毛細水三種類型,非飽和土中的吸力可分為吸附作用力、吸附毛細作用力和毛細作用力。結合水在自然條件下的遷移可以忽略不計,處于毛細角邊水狀態(tài)的非飽和土以氣態(tài)水遷移為主,當非飽和土中的毛細水連通時,水分以液態(tài)水遷移為主,并給出了非飽和土黃土結合水、毛細角邊水和毛細水的界限含水量。進一步在物理化學相關原理的基礎上給出了吸附作用力的理論計算公式,吸附作用力可以通過結合水化學勢能的減小量來衡量;基于分析非飽和土中吸附毛細作用力的作用效應,給出了吸附毛細作用力的確定方法;基于非飽和土力學原理列出了毛細作用力的確定方法,并對其適用性進行了評述。固-液接觸角的不易確定性和孔徑分布的隨機性致使毛細作用力的理論計算公式難以在實際中應用,因此,往往通過以陶瓷板為代表的高進氣材料來測定土體中的吸力�；趯λ�-氣-陶瓷板-非飽和土測試系統(tǒng)的分析,給出了毛細作用力量測時適宜的含水量范圍,只有當非飽和土中的毛細水處于聯(lián)通狀態(tài)時才可以通過該系統(tǒng)量測非飽和土中的吸力。基于上述分析,選擇毛細水連通的非飽和黃土,開展了其在基質(zhì)勢梯度作用下的水分遷移試驗。試驗結果表明,毛細水連通狀態(tài)下的非飽和黃土中的水分遷移量大體上隨著基質(zhì)勢梯度的增加而增加,并建立了水分遷移量與基質(zhì)勢梯度之間的統(tǒng)計關系式,可為評價基質(zhì)勢梯度對水分遷移的驅動作用所參考。進一步針對黃土高原旱區(qū)淺層土體水分場隨氣候變化問題,開展了非飽和黃土在溫度梯度作用下的氣態(tài)水遷移和液態(tài)水遷移試驗。試驗結果表明,氣態(tài)水遷移量和液態(tài)水遷移量均隨著溫度梯度的增加而增加,氣態(tài)水遷移量的增加幅度顯著大于液態(tài)水遷移量的增加幅度。在氣態(tài)水遷移中,溫度效應隨著土樣初始含水量的增加而顯著增加;在液態(tài)水遷移中,溫度效應與土樣初始含水量的關系不大。在對試驗結果分析的基礎上,建立了綜合考慮溫度梯度和初始含水量影響的非飽和黃土穩(wěn)態(tài)時含水量梯度的關系式。最后,在上述研究成果的基礎上完善了非飽和土二維非穩(wěn)態(tài)有限元計算方法,并對黃土高原淺層土體水分場在連續(xù)干旱條件下的動態(tài)變化進行了數(shù)值分析。水分場的數(shù)值計算結果與實測結果較為一致,表明了用數(shù)值計算預測淺層黃土水分場動態(tài)變化的可靠性�；趯崪y和計算結果,分析得到了黃土高原旱區(qū)淺層土體水分場在連續(xù)干旱條件下的變化規(guī)律以及土層含水量在不同干旱時間范圍內(nèi)的減小程度,可以為黃土高原旱區(qū)植物防護工程建設所參考。
[Abstract]:Unsaturated loess is all over the loess plateau and its water status has a significant impact on its engineering properties. The results show that the content of the combined water in the loess is mainly related to the content of the clay minerals, and the content of the clay minerals increases with the increase of the content of the clay minerals. The relation between water content and clay mineral content of different types is established, and the density and water film thickness of different types of combined water are determined by the combination of experimental and theoretical analysis. The suction force is an important variable which influences the seepage of unsaturated soil, and the soil body with different water content level can have different suction types. It has different influence on the seepage problem. At present, the study on the classification of suction force is still lacking for the seepage problem of unsaturated soil. For this purpose, on the basis of analyzing the occurrence state of pore water and its suction effect, the pore water in unsaturated soil is three types of combined water, capillary angle edge water and communication capillary water, and the suction force in unsaturated soil can be divided into adsorption force, adsorption capillary force and capillary force. the migration of the combined water under natural conditions is negligible, and the unsaturated soil in the water state of the capillary angle is mainly transferred by the gaseous water, and when the capillary water in the unsaturated soil is in communication, the water is mainly transported by the liquid water, and the unsaturated soil loess is combined with water, The boundary water content of the capillary water and the capillary water. The theoretical calculation formula of the adsorption force is given on the basis of the physical and chemical related principle, and the adsorption force can be measured by combining the reduction of the water chemical potential energy; and based on the action effect of the adsorption capillary force in the unsaturated soil, The determination method of the adsorption capillary force is given, and the determination method of the capillary force is listed on the basis of the principle of unsaturated soil mechanics, and the applicability of the method is reviewed. The uncertainty of the solid-liquid contact angle and the randomness of the pore size distribution make the theoretical calculation formula of the capillary force difficult to apply in practice, and therefore, the suction force in the soil body is often determined by the high intake material represented by the ceramic plate. Based on the analysis of the water-gas-ceramic plate-unsaturated soil test system, the water content range of the water-gas-ceramic plate-unsaturated soil test system is given, and the suction force in the unsaturated soil can be measured by the system only when the capillary water in the unsaturated soil is in the communication state. Based on the above analysis, the unsaturated loess with capillary water communication is selected, and the water migration test under the influence of the matrix potential gradient is carried out. The experimental results show that the amount of water migration in the unsaturated loess in the capillary water communication is generally increased with the increase of the matrix potential gradient, and the statistical relation between the moisture migration amount and the matrix potential gradient is established. It can be used to evaluate the driving effect of the matrix potential gradient on the migration of water. In the light of the problem of climate change, the water migration and liquid water migration test of unsaturated loess under the action of temperature gradient are carried out in the light of the problem of climate change. The experimental results show that both the amount of gas migration and the amount of liquid water migration increase with the increase of the temperature gradient, and the increase of the amount of gas migration is significantly higher than that of liquid water. In the gas migration, the temperature effect is obviously increased with the increase of the initial water content of the soil sample; in the liquid water migration, the temperature effect is not related to the initial water content of the soil sample. On the basis of the analysis of the test results, the relationship of the water content gradient of unsaturated loess with the influence of temperature gradient and initial water content is established. Finally, on the basis of the above research results, the two-dimensional non-steady-state finite element method of unsaturated soil is improved, and the dynamic changes of the water field of the shallow soil in the Loess Plateau under continuous drought conditions are analyzed. The numerical results of the water field are consistent with the measured results, and the reliability of the dynamic change of the water field of the shallow loess is predicted by numerical calculation. Based on the measured and calculated results, the variation law of the moisture field of the shallow soil in the arid area of the Loess Plateau and the degree of reduction of the water content of the soil layer in the range of different drought time are obtained, which can be referred to in the construction of plant protection in the dry area of the Loess Plateau.
【學位授予單位】：西安建筑科技大學
【學位級別】：博士
【學位授予年份】：2015
【分類號】：TU444
[Abstract]:Unsaturated loess is all over the loess plateau and its water status has a significant impact on its engineering properties. The results show that the content of the combined water in the loess is mainly related to the content of the clay minerals, and the content of the clay minerals increases with the increase of the content of the clay minerals. The relation between water content and clay mineral content of different types is established, and the density and water film thickness of different types of combined water are determined by the combination of experimental and theoretical analysis. The suction force is an important variable which influences the seepage of unsaturated soil, and the soil body with different water content level can have different suction types. It has different influence on the seepage problem. At present, the study on the classification of suction force is still lacking for the seepage problem of unsaturated soil. For this purpose, on the basis of analyzing the occurrence state of pore water and its suction effect, the pore water in unsaturated soil is three types of combined water, capillary angle edge water and communication capillary water, and the suction force in unsaturated soil can be divided into adsorption force, adsorption capillary force and capillary force. the migration of the combined water under natural conditions is negligible, and the unsaturated soil in the water state of the capillary angle is mainly transferred by the gaseous water, and when the capillary water in the unsaturated soil is in communication, the water is mainly transported by the liquid water, and the unsaturated soil loess is combined with water, The boundary water content of the capillary water and the capillary water. The theoretical calculation formula of the adsorption force is given on the basis of the physical and chemical related principle, and the adsorption force can be measured by combining the reduction of the water chemical potential energy; and based on the action effect of the adsorption capillary force in the unsaturated soil, The determination method of the adsorption capillary force is given, and the determination method of the capillary force is listed on the basis of the principle of unsaturated soil mechanics, and the applicability of the method is reviewed. The uncertainty of the solid-liquid contact angle and the randomness of the pore size distribution make the theoretical calculation formula of the capillary force difficult to apply in practice, and therefore, the suction force in the soil body is often determined by the high intake material represented by the ceramic plate. Based on the analysis of the water-gas-ceramic plate-unsaturated soil test system, the water content range of the water-gas-ceramic plate-unsaturated soil test system is given, and the suction force in the unsaturated soil can be measured by the system only when the capillary water in the unsaturated soil is in the communication state. Based on the above analysis, the unsaturated loess with capillary water communication is selected, and the water migration test under the influence of the matrix potential gradient is carried out. The experimental results show that the amount of water migration in the unsaturated loess in the capillary water communication is generally increased with the increase of the matrix potential gradient, and the statistical relation between the moisture migration amount and the matrix potential gradient is established. It can be used to evaluate the driving effect of the matrix potential gradient on the migration of water. In the light of the problem of climate change, the water migration and liquid water migration test of unsaturated loess under the action of temperature gradient are carried out in the light of the problem of climate change. The experimental results show that both the amount of gas migration and the amount of liquid water migration increase with the increase of the temperature gradient, and the increase of the amount of gas migration is significantly higher than that of liquid water. In the gas migration, the temperature effect is obviously increased with the increase of the initial water content of the soil sample; in the liquid water migration, the temperature effect is not related to the initial water content of the soil sample. On the basis of the analysis of the test results, the relationship of the water content gradient of unsaturated loess with the influence of temperature gradient and initial water content is established. Finally, on the basis of the above research results, the two-dimensional non-steady-state finite element method of unsaturated soil is improved, and the dynamic changes of the water field of the shallow soil in the Loess Plateau under continuous drought conditions are analyzed. The numerical results of the water field are consistent with the measured results, and the reliability of the dynamic change of the water field of the shallow loess is predicted by numerical calculation. Based on the measured and calculated results, the variation law of the moisture field of the shallow soil in the arid area of the Loess Plateau and the degree of reduction of the water content of the soil layer in the range of different drought time are obtained, which can be referred to in the construction of plant protection in the dry area of the Loess Plateau.
【學位授予單位】：西安建筑科技大學
【學位級別】：博士
【學位授予年份】：2015
【分類號】：TU444
【參考文獻】
相關期刊論文 前10條
1 Man CHENG;Shao Shan AN;;Responses of soil nitrogen, phosphorous and organic matter to vegetation succession on the Loess Plateau of China[J];Journal of Arid Land;2015年02期
2 錢峰;程冬兵;劉靜君;;土壤蒸發(fā)強度隨土壤溶液鹽分的變化研究[J];長江科學院院報;2015年03期
3 楊松;龔愛民;吳s，
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