華北平原弱透水層化學(xué)滲透效應(yīng)的試驗(yàn)研究及其數(shù)值模擬
發(fā)布時(shí)間：2019-01-10 14:50
【摘要】：低滲透粘性土或沉積物中的地下水流和溶質(zhì)運(yùn)移問題是地下水領(lǐng)域內(nèi)的一項(xiàng)重要研究課題。與傳統(tǒng)的高滲透性介質(zhì)中地下水流問題不同的是,低滲透介質(zhì)會(huì)表現(xiàn)出與生物膜類似的"半透膜"性質(zhì),其內(nèi)的地下水流不僅會(huì)受到水力梯度的驅(qū)動(dòng),而且還會(huì)受到濃度梯度(化學(xué)滲透)、電壓(電滲)以及溫差(熱滲)等組成的共軛梯度場(chǎng)的驅(qū)動(dòng),其中,化學(xué)滲透的驅(qū)動(dòng)作用最為明顯。近年來,這種由不同梯度驅(qū)動(dòng)的低滲透介質(zhì)耦合流問題被越來越多不同領(lǐng)域的研究所關(guān)注。然而,我國(guó)關(guān)于粘土半透膜效應(yīng)的化學(xué)滲透研究鮮有涉及。為此,本文從化學(xué)滲透的角度著力討論華北平原典型咸淡水界面的下移機(jī)理。論文首先綜述了研究背景、意義以及粘土半透膜效應(yīng)的化學(xué)滲透研究現(xiàn)狀,包括室內(nèi)試驗(yàn)、場(chǎng)地試驗(yàn)和化學(xué)滲透現(xiàn)象的野外證據(jù)等。針對(duì)粘土的"雙電層"理論總結(jié)了評(píng)估粘土膜性能的多個(gè)不連續(xù)模型。通過對(duì)比驗(yàn)證發(fā)現(xiàn),化學(xué)滲透率系數(shù)(σ)隨著陽(yáng)離子交換容量(CEC)的增大而增大;而隨著孔隙度、溶質(zhì)濃度的增加,σ減小。為了更加深入了解粘土的半透膜效應(yīng),本文利用自主設(shè)計(jì)的硬壁式滲透儀對(duì)華北平原典型咸淡水含水層間弱透水層的原狀土及利用原狀土加工制作的重塑土分別進(jìn)行了滲透率與化學(xué)滲透率系數(shù)σ的測(cè)定。通過滲透試驗(yàn),在濃度差為0.152M的濃度梯度下,測(cè)得原狀土的σ=0.013;重塑土 σ=0.089。對(duì)兩種土樣來說,雖然具有同樣的成分及孔隙度,但原狀土的膜性能明顯小于重塑土。這是由于重塑土較原狀土的粘土顆粒排列更加規(guī)則,因而表現(xiàn)出更高的膜性能。通過反滲透(超濾)試驗(yàn),在10m水頭差以及0.1092M濃度差的作用下,原狀土在水頭升高時(shí)發(fā)生破裂未測(cè)得相應(yīng)的σ,重塑土的σ=0.28,在20m的水頭差下,重塑土的σ=0.238,遠(yuǎn)大于化學(xué)滲透法測(cè)得的σ。同時(shí),討論了基于不同不連續(xù)模型估測(cè)的σ,與試驗(yàn)結(jié)果對(duì)比表明,Bresler模型與實(shí)際結(jié)果相對(duì)比較匹配。為擬合試驗(yàn)中的壓力差及濃度差隨時(shí)間瞬時(shí)變化的關(guān)系,引入一種連續(xù)模型對(duì)室內(nèi)試驗(yàn)結(jié)果進(jìn)行模擬,結(jié)果表明,如果參數(shù)賦值合理,連續(xù)模型可以很好地?cái)M合試驗(yàn)過程,尤其該連續(xù)模型還能對(duì)Noy et al.(2004)的場(chǎng)地試驗(yàn)結(jié)果進(jìn)行擬合。此外,對(duì)模型的各個(gè)參數(shù)進(jìn)行敏感性分析,由此確定了不同參數(shù)對(duì)壓力曲線進(jìn)化過程的影響程度。其中,σ主要影響壓力峰值的大小,彌散度D主要影響壓力曲線到達(dá)峰值后的衰減速率,而粘土的滲透率k與多孔石的彈性釋(貯)水系數(shù)Ss對(duì)壓力曲線到達(dá)峰值的時(shí)間影響很大。最后,選擇華北平原咸淡水典型區(qū)的衡水市桃城區(qū),將本文確定的咸淡水界面下移情況與前人的研究進(jìn)行了對(duì)比,發(fā)現(xiàn)下移速度較緩�？紤]到該區(qū)的粘性土層具有一定的膜性能,認(rèn)為該區(qū)含水層系統(tǒng)形成了一個(gè)典型的化學(xué)滲透系統(tǒng),產(chǎn)生的化學(xué)滲透壓力一定程度的抵消了由于過采深層淡水導(dǎo)致的向下的水頭差,從而減緩了咸淡水界面的下移速率。同時(shí),在華北平原典型咸淡水剖面上利用連續(xù)模型對(duì)剖面上滲透壓力的演化進(jìn)行模擬,剖面東部由于濃度差較大而具有更高的向上的滲透壓力,第Ⅲ、Ⅳ含水層由于厚度大較第Ⅱ含水層更晚的到達(dá)壓力峰值。在不考慮人為因素以及其他地質(zhì)構(gòu)造作用的情況下,一些地區(qū)的滲透壓力峰值可以達(dá)到近60m。因此,在華北平原咸-淡含水層間的弱透水層普遍存在著化學(xué)滲透現(xiàn)象。顯然,在研究該區(qū)咸淡水界面下移機(jī)理時(shí),不能忽略咸-淡含水層間粘性土的化學(xué)滲透效應(yīng)對(duì)咸淡水界面下移的影響。
[Abstract]:The problem of groundwater flow and solute transport in low-permeability cohesive soil or sediment is an important research subject in the field of groundwater. in contrast to the problem of the flow of groundwater in a conventional high-permeability medium, the low-permeability medium will exhibit similar "semi-permeable membrane" properties as the bio-film, with the groundwater flow in it not only being driven by a hydraulic gradient, but also by a concentration gradient (chemical penetration), The electro-osmotic pressure (electroosmosis) and temperature difference (heat-infiltration) are the driving of the co-static gradient field, and the driving effect of the chemical penetration is the most obvious. In recent years, this problem of coupled flow of low-permeability media driven by different gradients is becoming more and more important in many different fields. However, there are few chemical permeation studies on the semi-permeable membrane effect of clay. In this paper, the mechanism of the downward movement of the typical salty fresh water interface in the North China Plain is discussed from the angle of chemical penetration. The paper first reviews the research background, significance and the research status of the chemical penetration of the clay semi-permeable membrane effect, including the indoor test, the field test and the field evidence of the chemical penetration. A number of discrete models for evaluating the performance of the clay film are summarized for the "double electric layer" theory of the clay. By contrast, the chemical permeability coefficient (CP) was increased with the increase of the cation exchange capacity (CEC), and with the increase of the porosity and the concentration of the solute, the concentration of the solute decreased. In order to get a better understanding of the semi-permeable membrane effect of the clay, this paper makes use of the self-designed hard-wall permeameter to measure the permeability and the chemical permeability coefficient of the undisturbed soil of the weak water-permeable layer between the typical saline and fresh water-bearing layers in the plain and the remolded soil made from the original soil. Through the penetration test, under the concentration gradient of 0.152M, the density of the undisturbed soil was measured to be 0.013, and the remodeled soil pressure was 0.089. For both soil samples, although the same component and porosity, the film performance of the undisturbed soil is obviously less than that of the remolded soil. This is due to the more regular arrangement of the clay particles in the undisturbed soil of the remolded soil, and thus exhibits a higher film performance. By means of reverse osmosis (ultrafiltration) test, under the action of the head difference of 10m and the difference of the concentration of 0.1092M, the undisturbed soil has not been measured at the elevation of the head, the pressure of the remodeled soil is 0.28, under the head difference of 20m, the pressure of the remodeled soil is 0.238, which is much larger than that measured by the chemical penetration method. At the same time, the results of the estimation of different discontinuous models are discussed, and the comparison between the results of the test and the test results shows that the Bresler model is relatively matched with the actual results. In order to simulate the pressure difference and the difference of the concentration difference over time in the fitting experiment, a continuous model is introduced to simulate the indoor test results. The results show that, if the parameter assignment is reasonable, the continuous model can fit the test process well. In particular, the continuous model can also fit the site test results of Noy et al. (2004). In addition, the sensitivity analysis of each parameter of the model is carried out, and the influence degree of different parameters on the evolution process of the pressure curve is determined. In this paper, the peak value of pressure is mainly affected by the pressure curve, and the dispersion degree D mainly affects the decay rate after the pressure curve reaches the peak value, and the time that the permeability k of the clay and the elastic release (storage) water system number Ss of the porous stone reach the peak value of the pressure curve is very large. In the end, we select the Taocheng District of Hengshui City, which is the typical area of the salt and fresh water in the North China Plain, and compare the downward movement of the salty fresh water interface determined in this paper with the previous research, and find that the moving speed is slower. Considering that the cohesive soil layer in this area has a certain membrane property, it is considered that the aquifer system of this area has formed a typical chemical permeation system, and the resulting chemical penetration pressure is partly offset by the downward head difference due to overproduction of deep fresh water, so as to slow down the down-down rate of the salty fresh water interface. At the same time, the evolution of the permeability pressure on the section is simulated by the continuous model in the typical salty fresh water section of the North China Plain, and the eastern section of the section has a higher upward permeation pressure due to the large concentration difference, and the third, The fourth aquifer reaches the pressure peak more late due to the larger thickness than the second aquifer. In the absence of human factors and other geological structures, the peak of the osmotic pressure in some areas can reach nearly 60m. Therefore, the phenomenon of chemical penetration is common in the weak water-permeable layer between the saline-fresh water-bearing layers in the North China Plain. It is clear that the effect of the chemical penetration effect of the cohesive soil between the brackish-water and the brackish fresh water is not neglected in the study of the down-moving mechanism of the brackish fresh water interface in this area.
【學(xué)位授予單位】：南京大學(xué)
【學(xué)位級(jí)別】：博士
【學(xué)位授予年份】：2017
【分類號(hào)】：P641.3
本文編號(hào)：2406441
[Abstract]:The problem of groundwater flow and solute transport in low-permeability cohesive soil or sediment is an important research subject in the field of groundwater. in contrast to the problem of the flow of groundwater in a conventional high-permeability medium, the low-permeability medium will exhibit similar "semi-permeable membrane" properties as the bio-film, with the groundwater flow in it not only being driven by a hydraulic gradient, but also by a concentration gradient (chemical penetration), The electro-osmotic pressure (electroosmosis) and temperature difference (heat-infiltration) are the driving of the co-static gradient field, and the driving effect of the chemical penetration is the most obvious. In recent years, this problem of coupled flow of low-permeability media driven by different gradients is becoming more and more important in many different fields. However, there are few chemical permeation studies on the semi-permeable membrane effect of clay. In this paper, the mechanism of the downward movement of the typical salty fresh water interface in the North China Plain is discussed from the angle of chemical penetration. The paper first reviews the research background, significance and the research status of the chemical penetration of the clay semi-permeable membrane effect, including the indoor test, the field test and the field evidence of the chemical penetration. A number of discrete models for evaluating the performance of the clay film are summarized for the "double electric layer" theory of the clay. By contrast, the chemical permeability coefficient (CP) was increased with the increase of the cation exchange capacity (CEC), and with the increase of the porosity and the concentration of the solute, the concentration of the solute decreased. In order to get a better understanding of the semi-permeable membrane effect of the clay, this paper makes use of the self-designed hard-wall permeameter to measure the permeability and the chemical permeability coefficient of the undisturbed soil of the weak water-permeable layer between the typical saline and fresh water-bearing layers in the plain and the remolded soil made from the original soil. Through the penetration test, under the concentration gradient of 0.152M, the density of the undisturbed soil was measured to be 0.013, and the remodeled soil pressure was 0.089. For both soil samples, although the same component and porosity, the film performance of the undisturbed soil is obviously less than that of the remolded soil. This is due to the more regular arrangement of the clay particles in the undisturbed soil of the remolded soil, and thus exhibits a higher film performance. By means of reverse osmosis (ultrafiltration) test, under the action of the head difference of 10m and the difference of the concentration of 0.1092M, the undisturbed soil has not been measured at the elevation of the head, the pressure of the remodeled soil is 0.28, under the head difference of 20m, the pressure of the remodeled soil is 0.238, which is much larger than that measured by the chemical penetration method. At the same time, the results of the estimation of different discontinuous models are discussed, and the comparison between the results of the test and the test results shows that the Bresler model is relatively matched with the actual results. In order to simulate the pressure difference and the difference of the concentration difference over time in the fitting experiment, a continuous model is introduced to simulate the indoor test results. The results show that, if the parameter assignment is reasonable, the continuous model can fit the test process well. In particular, the continuous model can also fit the site test results of Noy et al. (2004). In addition, the sensitivity analysis of each parameter of the model is carried out, and the influence degree of different parameters on the evolution process of the pressure curve is determined. In this paper, the peak value of pressure is mainly affected by the pressure curve, and the dispersion degree D mainly affects the decay rate after the pressure curve reaches the peak value, and the time that the permeability k of the clay and the elastic release (storage) water system number Ss of the porous stone reach the peak value of the pressure curve is very large. In the end, we select the Taocheng District of Hengshui City, which is the typical area of the salt and fresh water in the North China Plain, and compare the downward movement of the salty fresh water interface determined in this paper with the previous research, and find that the moving speed is slower. Considering that the cohesive soil layer in this area has a certain membrane property, it is considered that the aquifer system of this area has formed a typical chemical permeation system, and the resulting chemical penetration pressure is partly offset by the downward head difference due to overproduction of deep fresh water, so as to slow down the down-down rate of the salty fresh water interface. At the same time, the evolution of the permeability pressure on the section is simulated by the continuous model in the typical salty fresh water section of the North China Plain, and the eastern section of the section has a higher upward permeation pressure due to the large concentration difference, and the third, The fourth aquifer reaches the pressure peak more late due to the larger thickness than the second aquifer. In the absence of human factors and other geological structures, the peak of the osmotic pressure in some areas can reach nearly 60m. Therefore, the phenomenon of chemical penetration is common in the weak water-permeable layer between the saline-fresh water-bearing layers in the North China Plain. It is clear that the effect of the chemical penetration effect of the cohesive soil between the brackish-water and the brackish fresh water is not neglected in the study of the down-moving mechanism of the brackish fresh water interface in this area.
【學(xué)位授予單位】：南京大學(xué)
【學(xué)位級(jí)別】：博士
【學(xué)位授予年份】：2017
【分類號(hào)】：P641.3
【參考文獻(xiàn)】
相關(guān)期刊論文 前3條
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2 席永慧;馮世進(jìn);;粘質(zhì)土壤的膜性能研究進(jìn)展[J];同濟(jì)大學(xué)學(xué)報(bào)(自然科學(xué)版);2009年02期
3 宋海波;張兆吉;費(fèi)宇紅;王振昌;錢永;衛(wèi)文;;開采條件下河北平原中部咸淡水界面下移[J];水文地質(zhì)工程地質(zhì);2007年01期
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