非飽和黃土水熱耦合數(shù)值模擬研究
發(fā)布時(shí)間：2019-03-28 12:03
【摘要】：非飽和黃土通常水分含量較低,在研究水運(yùn)移過程中,往往忽略了氣態(tài)水遷移的作用。中國西北地區(qū)黃土地下水位很低,但諸如城市和機(jī)場(chǎng)硬化路面以下土層含水率卻較高,這種現(xiàn)象已經(jīng)不能使用經(jīng)典的熱和液態(tài)水遷移理論來解釋。通過分析文獻(xiàn)資料和揭示現(xiàn)場(chǎng)“鍋蓋”效應(yīng)現(xiàn)象的研究需要,提出了一種用于模擬非飽和黃土中水分和熱耦合的新思路,該理論認(rèn)為水分遷移受到溫度梯度和基質(zhì)吸力梯度的雙重作用,其不僅考慮了土中液態(tài)水的遷移和熱量的傳遞,還考慮了液態(tài)水和氣態(tài)水之間的相變轉(zhuǎn)換(蒸發(fā)和冷凝)及相變潛熱和顯熱。通過建立非飽和黃土模型和水分遷移質(zhì)量和能量守恒方程,改變初始條件和邊界溫度,并使用數(shù)值軟件Comsol Multiphysics對(duì)其進(jìn)行模擬,得出了氣態(tài)水和液態(tài)水在水分遷移過程中的運(yùn)移基本規(guī)律和相對(duì)貢獻(xiàn)大小及其條件,以及在不同溫度梯度、溫度水平、初始含水率、遷移時(shí)間和土水特性參數(shù)等情況下,水分分布變化規(guī)律。通過研究得出如下結(jié)果:在溫度梯度作用下,土體中的水分主要以氣態(tài)水分形式由高溫端向低溫端運(yùn)移,當(dāng)氣態(tài)水在低溫端凝結(jié)成液態(tài)水時(shí),水分又會(huì)在吸力梯度作用下以液態(tài)水形式向高溫端運(yùn)移;土體模型(20厘米)中溫度場(chǎng)在10小時(shí)后就基本達(dá)到了穩(wěn)定,溫度梯度不再變化;隨著土體溫度梯度、溫度水平和遷移時(shí)間的逐漸增大,高(低)溫端水分遷出(入)量越大,土中含水率增量為0的臨界點(diǎn)距高溫端越遠(yuǎn),水分流失區(qū)域越大,總水分遷移量也越大;隨著土體初始含水率逐漸增大,高溫端水分遷出量逐漸增大;而低溫端水分遷入量先增大,當(dāng)含水率達(dá)到某一值時(shí),氣態(tài)水的遷移通道越來越小,水分遷入量減小,水分流失區(qū)域逐漸減小,因此,土體中總水分遷移量是先增大后減小,土中含水率增量為0的臨界點(diǎn)距高溫端越近,臨界點(diǎn)附近曲線變化趨勢(shì)越發(fā)突變。隨著與進(jìn)氣值有關(guān)的參數(shù)的不斷增大,高(低)溫端水分遷出(入)量越大,土中含水率分布曲線在高(低)溫端處越陡,含水率增量為0的臨界點(diǎn)距高溫端越近,臨界點(diǎn)附近曲線變化趨勢(shì)較大;隨著與土水特征曲線減濕斜率有關(guān)的參數(shù)的逐漸增大,高(低)溫端水分遷出(入)量越小,土中含水率分布曲線越平緩,含水率增量為0的臨界點(diǎn)距高溫端越遠(yuǎn)。
[Abstract]:The water content of unsaturated loess is usually low, and the role of gaseous water migration is often neglected in the study of water migration. The loess groundwater level in northwest China is very low, but the soil moisture content below the hardened pavement in cities and airports is relatively high. This phenomenon can no longer be explained by the classical thermal and liquid water transfer theory. Based on the analysis of the literature and the need to reveal the phenomenon of "pot cover" effect in the field, a new idea for simulating the coupling of moisture and heat in unsaturated loess is put forward. According to the theory, water transfer is affected by both temperature gradient and matrix suction gradient, which not only takes into account the transfer of liquid water and heat transfer in soil, but also takes into account the effect of temperature gradient and matrix suction gradient. The phase transition (evaporation and condensation) and latent and sensible heat between liquid and gaseous water are also considered. Through the establishment of unsaturated loess model and conservation equation of moisture transfer mass and energy, the initial conditions and boundary temperature are changed, and the numerical software Comsol Multiphysics is used to simulate it. The basic law and relative contribution of gaseous water and liquid water in the process of water migration are obtained, and under the conditions of different temperature gradient, temperature level, initial moisture content, migration time and soil water characteristic parameters, etc. Law of change of water distribution. The results are as follows: under the action of temperature gradient, the moisture in the soil moves mainly from the high temperature end to the low temperature end in the form of gaseous water, and when the gaseous water condenses at the low temperature end to liquid water, The water will move to the high temperature end in the form of liquid water under the action of suction gradient. In the soil model (20 cm), the temperature field is stable after 10 hours, and the temperature gradient is no longer changed. With the gradual increase of soil temperature gradient, temperature level and migration time, the greater the amount of water migration (inflow) at the high (low) temperature end, the farther the critical point with the increment of water content 0 in the soil from the high temperature end, and the larger the water loss area is. The total water migration also increased; As the initial moisture content of soil increases gradually, the water mobility at the high temperature end increases gradually. When the moisture content reaches a certain value, the migration channel of gaseous water becomes smaller and smaller, the water migration volume decreases, and the water loss area decreases gradually. Therefore, the total water migration amount in the soil increases first and then decreases, and when the water content reaches a certain value, the migration channel of gaseous water becomes smaller and smaller. The closer the critical point of soil moisture content increment is to the high temperature end, the more abrupt the change trend of the curve near the critical point is. With the increasing of the parameters related to the inlet value, the greater the water migration (inflow) amount at the high (low) temperature end, the steeper the water content distribution curve in the soil at the high (low) temperature end, and the nearer the critical point at which the moisture content increment is 0 is closer to the high temperature end. The curve near the critical point has a great trend of change; With the increasing of the parameters related to the moisture reduction slope of the soil-water characteristic curve, the smaller the water migration (inflow) amount at the high (low) temperature end is, the more smooth the moisture content distribution curve in the soil is, and the farther the critical point at which the moisture content increment is 0 is from the high-temperature end.
【學(xué)位授予單位】：西安理工大學(xué)
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2017
【分類號(hào)】：TU444
本文編號(hào)：2448840
[Abstract]:The water content of unsaturated loess is usually low, and the role of gaseous water migration is often neglected in the study of water migration. The loess groundwater level in northwest China is very low, but the soil moisture content below the hardened pavement in cities and airports is relatively high. This phenomenon can no longer be explained by the classical thermal and liquid water transfer theory. Based on the analysis of the literature and the need to reveal the phenomenon of "pot cover" effect in the field, a new idea for simulating the coupling of moisture and heat in unsaturated loess is put forward. According to the theory, water transfer is affected by both temperature gradient and matrix suction gradient, which not only takes into account the transfer of liquid water and heat transfer in soil, but also takes into account the effect of temperature gradient and matrix suction gradient. The phase transition (evaporation and condensation) and latent and sensible heat between liquid and gaseous water are also considered. Through the establishment of unsaturated loess model and conservation equation of moisture transfer mass and energy, the initial conditions and boundary temperature are changed, and the numerical software Comsol Multiphysics is used to simulate it. The basic law and relative contribution of gaseous water and liquid water in the process of water migration are obtained, and under the conditions of different temperature gradient, temperature level, initial moisture content, migration time and soil water characteristic parameters, etc. Law of change of water distribution. The results are as follows: under the action of temperature gradient, the moisture in the soil moves mainly from the high temperature end to the low temperature end in the form of gaseous water, and when the gaseous water condenses at the low temperature end to liquid water, The water will move to the high temperature end in the form of liquid water under the action of suction gradient. In the soil model (20 cm), the temperature field is stable after 10 hours, and the temperature gradient is no longer changed. With the gradual increase of soil temperature gradient, temperature level and migration time, the greater the amount of water migration (inflow) at the high (low) temperature end, the farther the critical point with the increment of water content 0 in the soil from the high temperature end, and the larger the water loss area is. The total water migration also increased; As the initial moisture content of soil increases gradually, the water mobility at the high temperature end increases gradually. When the moisture content reaches a certain value, the migration channel of gaseous water becomes smaller and smaller, the water migration volume decreases, and the water loss area decreases gradually. Therefore, the total water migration amount in the soil increases first and then decreases, and when the water content reaches a certain value, the migration channel of gaseous water becomes smaller and smaller. The closer the critical point of soil moisture content increment is to the high temperature end, the more abrupt the change trend of the curve near the critical point is. With the increasing of the parameters related to the inlet value, the greater the water migration (inflow) amount at the high (low) temperature end, the steeper the water content distribution curve in the soil at the high (low) temperature end, and the nearer the critical point at which the moisture content increment is 0 is closer to the high temperature end. The curve near the critical point has a great trend of change; With the increasing of the parameters related to the moisture reduction slope of the soil-water characteristic curve, the smaller the water migration (inflow) amount at the high (low) temperature end is, the more smooth the moisture content distribution curve in the soil is, and the farther the critical point at which the moisture content increment is 0 is from the high-temperature end.
【學(xué)位授予單位】：西安理工大學(xué)
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2017
【分類號(hào)】：TU444
【參考文獻(xiàn)】
相關(guān)期刊論文 前10條
1 王華軍;路俊超;楊賓;齊承英;;溫度梯度下土壤鹽分遷移過程的數(shù)值模擬[J];太陽能學(xué)報(bào);2014年06期
2 邵龍?zhí)?;飽和土的土骨架應(yīng)力方程[J];巖土工程學(xué)報(bào);2011年12期
3 王華軍;齊承英;;土壤高溫儲(chǔ)熱熱濕遷移過程的初步研究[J];太陽能學(xué)報(bào);2009年12期
4 楊洋;姚海林;盧正;;蒸發(fā)條件下路基對(duì)氣候變化的響應(yīng)模型及影響因素分析[J];巖土力學(xué);2009年05期
5 王鐵行;;非飽和黃土路基水分場(chǎng)的數(shù)值分析[J];巖土工程學(xué)報(bào);2008年01期
6 王鐵行,賀再球,趙樹德,孫建樂;非飽和土體氣態(tài)水遷移試驗(yàn)研究[J];巖石力學(xué)與工程學(xué)報(bào);2005年18期
7 駱祖江,劉昌軍,瞿成松,羅建軍;深基坑降水疏干過程中三維滲流場(chǎng)數(shù)值模擬研究[J];水文地質(zhì)工程地質(zhì);2005年05期
8 王鐵行,李寧,謝定義;土體水熱力耦合問題研究意義、現(xiàn)狀及建議[J];巖土力學(xué);2005年03期
9 王鐵行,李寧,謝定義;非飽和黃土重力勢(shì)、基質(zhì)勢(shì)和溫度勢(shì)探討[J];巖土工程學(xué)報(bào);2004年05期
10 王鐵行,陸海紅;溫度影響下的非飽和黃土水分遷移問題探討[J];巖土力學(xué);2004年07期
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