非飽和土水特征曲線的溫度效應(yīng)研究
發(fā)布時間：2018-07-15 09:19
【摘要】：非飽和土水特征曲線通常定義為土中基質(zhì)吸力s（kPa）與重力含水量w或體積含水量θ、飽和度S之間的關(guān)系。它反映了土壤的儲水和釋水性質(zhì)，與孔隙結(jié)構(gòu)和孔徑分布密切相關(guān)，可以用于預(yù)測非飽和滲透性函數(shù)、抗剪強(qiáng)度等物理和力學(xué)參數(shù)，，因此在非飽和土力學(xué)中有著非常重要的意義。影響土水特征曲線的因素有很多，如滯回性、液體粘滯性影響、應(yīng)力狀態(tài)影響、應(yīng)力歷史影響、顆粒級配等，這些因素對土壤的持水能力影響很大，因而引起了眾多學(xué)者的關(guān)注。相比較而言，自然環(huán)境中溫度的變化是不大的，其對土壤持水能力的影響體現(xiàn)得并不顯著，所以往往被忽視。但隨著科學(xué)技術(shù)的不斷進(jìn)步，巖土工程領(lǐng)域所涉及的問題越來越復(fù)雜，如地下核廢料的處置、二氧化碳地下封存、地?zé)豳Y源開發(fā)、石油開采、高壓電纜的埋設(shè)等，更多的工程設(shè)施將承受較大的溫度變化。此時，溫度對土水特征曲線的影響變得不可忽略。目前，對于如何獲取考慮溫度影響的土水特征曲線以及其影響機(jī)理，學(xué)者們還沒有達(dá)成一致意見。 本研究開發(fā)了一套高精度土水特征曲線自動測試系統(tǒng)，開展了不同溫度作用下粉土質(zhì)砂土水特征曲線試驗，討論和分析了溫度影響下非飽和土水特征曲線的變化規(guī)律及溫度的作用機(jī)制，并建立了考慮溫度影響的土水特征曲線預(yù)測模型，進(jìn)行了一維土柱非飽和土蒸發(fā)試驗與數(shù)值分析。研究的主要內(nèi)容及結(jié)論如下： 1）研制了一套高精度土水特征曲線自動測試系統(tǒng)。該系統(tǒng)實現(xiàn)了整個測試過程的全自動化控制，同時提高了氣壓力控制精度、修正了每一級氣壓下排水體積量和實現(xiàn)了對試驗溫度的控制，在滿足特定試驗需求的同時提高了試驗效率和保證了試驗的精度，特別適用于粗顆粒土的相關(guān)試驗測試。為了實現(xiàn)儀器的規(guī)范化操作，還特別編制了儀器的操作規(guī)程，介紹了儀器操作注意事項，為后續(xù)試驗提供了技術(shù)支持。 2）將高精度土水特征曲線自動測試系統(tǒng)置于溫控箱中，開展了4種不同溫度作用下粉土質(zhì)砂的土水特征曲線試驗，并與其他學(xué)者的相關(guān)試驗數(shù)據(jù)對比，討論和分析了溫度影響下非飽和土水特征曲線的變化規(guī)律及溫度的作用機(jī)制。結(jié)果表明，溫度對非飽和土水特征曲線的影響不可忽略，隨著溫度的升高土壤的進(jìn)氣值和殘余含水量均在減小，基質(zhì)吸力相同時，土壤的體積含水量隨溫度上升逐漸減小，土壤顆粒大小和孔隙尺寸分布的不同導(dǎo)致溫度對粉土質(zhì)砂、粉質(zhì)土、粘性土和膨脹土的土水特征曲線的影響出現(xiàn)局部的差異性。 3）以熱力學(xué)及非飽和土相關(guān)理論為基礎(chǔ)，考慮表面張力、浸潤角和吸力的溫度效應(yīng)，借助于van Genuchten模型，在分析研究模型中各參數(shù)隨溫度變化規(guī)律的同時建立了考慮溫度影響的土水特征曲線預(yù)測模型。通過將預(yù)測結(jié)果與實測數(shù)據(jù)進(jìn)行對比可以發(fā)現(xiàn)該模型具有較好的適用性。對于粘粒含量較大的土，由于忽略了溫度對顆粒表面水合作用的影響，在基質(zhì)吸力大于進(jìn)氣值的區(qū)段，預(yù)測結(jié)果與實測結(jié)果存在一定的偏差。 4）研制了可變環(huán)境條件自動蒸滲測量系統(tǒng)，開展了一維土柱室內(nèi)蒸發(fā)試驗，同時采用非飽和土水-熱遷移方程及相關(guān)預(yù)測參數(shù)對蒸發(fā)條件下土壤水分的運動進(jìn)行了數(shù)值模擬，最后將數(shù)值計算結(jié)果與實測試驗結(jié)果進(jìn)行對比，檢驗了水-熱遷移方程及相關(guān)預(yù)測參數(shù)的可靠性。結(jié)果表明，非飽和土的蒸發(fā)過程可分為三個階段：穩(wěn)定階段、減速階段、殘余階段。隨著蒸發(fā)的持續(xù)進(jìn)行，土柱縱剖面上含水量開始出現(xiàn)明顯的梯度，干-濕界面從土表開始形成并隨著蒸發(fā)的進(jìn)行不斷向下推移。數(shù)值計算結(jié)果與實測值基本吻合，說明該計算模型及相關(guān)參數(shù)的選取是合理的，所得的結(jié)論是可靠的。 論文創(chuàng)新點：開展了考慮溫度影響的非飽和土水特征曲線試驗研究，并進(jìn)行了影響機(jī)理分析；建立了考慮溫度影響的土水特征曲線預(yù)測模型，并應(yīng)用于蒸發(fā)條件下土壤水分運動的數(shù)值模擬研究。
[Abstract]:The characteristic curve of unsaturated soil water is usually defined as the relationship between matrix suction s (kPa) and gravity water content w or volumetric water content [theta] and saturation S. It reflects soil water storage and water release properties, closely related to pore structure and pore size distribution, and can be used to predict unsaturated permeability function, shear strength and other physical and mechanical parameters. Therefore, there are very important significance in the mechanics of unsaturated soil. There are many factors affecting the soil water characteristic curve, such as hysteresis, the influence of liquid viscosity, stress state, stress history and particle gradation. These factors have great influence on the water holding capacity of the soil, so many scholars pay attention to it. The change in temperature is not significant in the environment, and its influence on soil water holding capacity is not obvious, so it is often ignored. But with the continuous progress of science and technology, the problems involved in the field of geotechnical engineering are becoming more and more complex, such as the disposal of underground nuclear waste, the underground seal of carbon dioxide, the development of geothermal resources, the exploitation of oil, the high voltage electricity. At this time, the influence of temperature on the soil water characteristic curve can not be ignored. At present, there is no agreement on how to obtain the soil water characteristic curve and its influence mechanism.
An automatic test system for high precision soil water characteristic curve is developed in this study. The water characteristic curve of silty soil under different temperatures is carried out. The variation law of unsaturated soil water characteristic curve and the mechanism of temperature effect under the influence of temperature are discussed and analyzed, and the prediction model of soil water characteristic curve with the influence of temperature is established. The evaporation test and numerical analysis of unsaturated soil in one dimension soil column are carried out. The main contents and conclusions are as follows:
1) a set of automatic test system for high precision soil water characteristic curve is developed. The system realizes full automation control of the whole test process, improves the control precision of pressure force, corrections the volume of drainage under each air pressure and realizes the control of the test temperature, and improves the test efficiency while meeting the specific test demand. The accuracy of the test is guaranteed. It is especially suitable for the test of coarse granular soil. In order to realize the standardized operation of the instrument, the operating regulations of the instrument are specially compiled, and the precautions for the operation of the instrument are introduced, and the technical support for the follow-up test is provided.
2) the automatic test system of high precision soil water characteristic curve is placed in the temperature control box, and the soil water characteristic curve of 4 kinds of silty sand under different temperatures is carried out. And compared with the related experimental data of other scholars, the change law of the characteristic curve of unsaturated soil water and the mechanism of temperature are discussed and analyzed under the influence of temperature. The influence of temperature on the characteristic curve of unsaturated soil water can not be ignored. With the increase of temperature, the intake and residual water content of soil decreased, and the volume of soil volume decreased with the temperature, and the size of soil particles and the distribution of pore size resulted in the temperature on silty sand, silty soil and stickiness. The influence of soil water characteristic curve of soil and expansive soil is local difference.
3) on the basis of the theory of thermodynamics and unsaturated soil, the temperature effect of surface tension, infiltration angle and suction is considered. With the help of van Genuchten model, the prediction model of soil water characteristic curve with the influence of temperature is established at the same time, and the prediction results are carried out with the measured data. The comparison can be found that the model has good applicability. For clay with larger clay content, there is a certain deviation between the predicted result and the measured result because of neglecting the effect of temperature on the hydration of the particle surface, and in the section of the matrix suction greater than the intake value.
4) the automatic vaporization measurement system with variable environment conditions was developed, and the indoor evaporation test of one dimension soil column was carried out. At the same time, the numerical simulation of soil moisture movement under the evaporation condition was simulated with the unsaturated soil water heat transfer equation and the related prediction parameters. Finally, the numerical results were compared with the experimental results, and the water heat migration was tested. The stability of the evaporation process of the unsaturated soil shows that the evaporation process of the unsaturated soil can be divided into three stages: the stable stage, the deceleration stage and the residual stage. With the continuous evaporation of the soil, the water content in the vertical section of the soil column begins to appear obvious gradient, the dry wet interface begins to form from the soil surface and continues down with the evaporation. The numerical results are basically consistent with the measured values, indicating that the calculation model and the selection of relevant parameters are reasonable, and the conclusions obtained are reliable.
The innovation points of this paper are as follows: the experimental study of unsaturated soil water characteristic curve with the influence of temperature is carried out, and the influence mechanism is analyzed. The prediction model of soil water characteristic curve with the influence of temperature is established and applied to the numerical simulation of soil water movement under the condition of evaporation.
【學(xué)位授予單位】：三峽大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2014
【分類號】：TU43
本文編號：2123577
[Abstract]:The characteristic curve of unsaturated soil water is usually defined as the relationship between matrix suction s (kPa) and gravity water content w or volumetric water content [theta] and saturation S. It reflects soil water storage and water release properties, closely related to pore structure and pore size distribution, and can be used to predict unsaturated permeability function, shear strength and other physical and mechanical parameters. Therefore, there are very important significance in the mechanics of unsaturated soil. There are many factors affecting the soil water characteristic curve, such as hysteresis, the influence of liquid viscosity, stress state, stress history and particle gradation. These factors have great influence on the water holding capacity of the soil, so many scholars pay attention to it. The change in temperature is not significant in the environment, and its influence on soil water holding capacity is not obvious, so it is often ignored. But with the continuous progress of science and technology, the problems involved in the field of geotechnical engineering are becoming more and more complex, such as the disposal of underground nuclear waste, the underground seal of carbon dioxide, the development of geothermal resources, the exploitation of oil, the high voltage electricity. At this time, the influence of temperature on the soil water characteristic curve can not be ignored. At present, there is no agreement on how to obtain the soil water characteristic curve and its influence mechanism.
An automatic test system for high precision soil water characteristic curve is developed in this study. The water characteristic curve of silty soil under different temperatures is carried out. The variation law of unsaturated soil water characteristic curve and the mechanism of temperature effect under the influence of temperature are discussed and analyzed, and the prediction model of soil water characteristic curve with the influence of temperature is established. The evaporation test and numerical analysis of unsaturated soil in one dimension soil column are carried out. The main contents and conclusions are as follows:
1) a set of automatic test system for high precision soil water characteristic curve is developed. The system realizes full automation control of the whole test process, improves the control precision of pressure force, corrections the volume of drainage under each air pressure and realizes the control of the test temperature, and improves the test efficiency while meeting the specific test demand. The accuracy of the test is guaranteed. It is especially suitable for the test of coarse granular soil. In order to realize the standardized operation of the instrument, the operating regulations of the instrument are specially compiled, and the precautions for the operation of the instrument are introduced, and the technical support for the follow-up test is provided.
2) the automatic test system of high precision soil water characteristic curve is placed in the temperature control box, and the soil water characteristic curve of 4 kinds of silty sand under different temperatures is carried out. And compared with the related experimental data of other scholars, the change law of the characteristic curve of unsaturated soil water and the mechanism of temperature are discussed and analyzed under the influence of temperature. The influence of temperature on the characteristic curve of unsaturated soil water can not be ignored. With the increase of temperature, the intake and residual water content of soil decreased, and the volume of soil volume decreased with the temperature, and the size of soil particles and the distribution of pore size resulted in the temperature on silty sand, silty soil and stickiness. The influence of soil water characteristic curve of soil and expansive soil is local difference.
3) on the basis of the theory of thermodynamics and unsaturated soil, the temperature effect of surface tension, infiltration angle and suction is considered. With the help of van Genuchten model, the prediction model of soil water characteristic curve with the influence of temperature is established at the same time, and the prediction results are carried out with the measured data. The comparison can be found that the model has good applicability. For clay with larger clay content, there is a certain deviation between the predicted result and the measured result because of neglecting the effect of temperature on the hydration of the particle surface, and in the section of the matrix suction greater than the intake value.
4) the automatic vaporization measurement system with variable environment conditions was developed, and the indoor evaporation test of one dimension soil column was carried out. At the same time, the numerical simulation of soil moisture movement under the evaporation condition was simulated with the unsaturated soil water heat transfer equation and the related prediction parameters. Finally, the numerical results were compared with the experimental results, and the water heat migration was tested. The stability of the evaporation process of the unsaturated soil shows that the evaporation process of the unsaturated soil can be divided into three stages: the stable stage, the deceleration stage and the residual stage. With the continuous evaporation of the soil, the water content in the vertical section of the soil column begins to appear obvious gradient, the dry wet interface begins to form from the soil surface and continues down with the evaporation. The numerical results are basically consistent with the measured values, indicating that the calculation model and the selection of relevant parameters are reasonable, and the conclusions obtained are reliable.
The innovation points of this paper are as follows: the experimental study of unsaturated soil water characteristic curve with the influence of temperature is carried out, and the influence mechanism is analyzed. The prediction model of soil water characteristic curve with the influence of temperature is established and applied to the numerical simulation of soil water movement under the condition of evaporation.
【學(xué)位授予單位】：三峽大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2014
【分類號】：TU43
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