本文選題：花崗巖殘積土 + 非飽和土　； 參考：《南昌大學(xué)》2017年博士論文

【摘要】：崩崗侵蝕是南方花崗巖地區(qū)土壤侵蝕最為嚴(yán)重的類型,而我省的贛南地區(qū)是崩崗侵蝕發(fā)育重災(zāi)區(qū)。影響邊坡崩崗侵蝕的因素是多方面的,水是最主要的外因,降雨入滲導(dǎo)致非飽和土邊坡含水量增加,從而導(dǎo)致土中的基質(zhì)吸力也相應(yīng)地發(fā)生變化,土體的強度等特性也相應(yīng)發(fā)生改變。贛南崩崗區(qū)以花崗巖風(fēng)化殼殘積土為主,該類土的物理力學(xué)性質(zhì)受水的影響顯著,同時還經(jīng)受干濕循環(huán)作用,開展該類土的非飽和土特性研究可以為贛南地區(qū)崩崗侵蝕機理研究和防治提供理論支持。本文將以花崗巖殘積土為研究對象,采用非飽和土三軸儀和壓力板儀等實驗儀器研究其強度和變形特征以及土水特征曲線的測定,開展基于貝葉斯理論的土水特征曲線預(yù)測研究,建立了采用有限數(shù)據(jù)對土水特征曲線有效地預(yù)測的方法,同時進(jìn)行土水特征曲線模型參數(shù)的不確定性分析,獲得土水特征曲線的置信區(qū)間,并應(yīng)用到降雨條件下的邊坡穩(wěn)定性分析中。(1)為探討崩崗區(qū)非飽和花崗巖殘積土強度和變形特性,利用非飽和土三軸儀對重塑土樣進(jìn)行控制吸力固結(jié)排水剪切試驗,研究干密度、凈圍壓和基質(zhì)吸力等因素對應(yīng)力-應(yīng)變關(guān)系、強度特性和體變特性的影響,分析非飽和花崗巖殘積土在控制吸力條件下的剪切性狀,研究表明其應(yīng)力-應(yīng)變關(guān)系取決于凈圍壓和基質(zhì)吸力兩者組合。通過分析基質(zhì)吸力對非飽和土強度的貢獻(xiàn)可知,基質(zhì)吸力對黏聚力有較大的影響,且呈線性增長趨勢,而對有效內(nèi)摩擦角影響則較小。同樣對石灰改良花崗巖殘積土進(jìn)行控制吸力固結(jié)排水剪切試驗,以研究石灰含量對非飽和改良土的強度和變形特性的影響,試驗分別采用摻灰比0%、4%和8%的改良花崗巖殘積土,同時還選用了兩種顆粒尺寸(1mm,2mm)花崗巖殘積土進(jìn)行了相關(guān)試驗,石灰改良土的黏聚力和摩擦角隨著石灰含量的增加而增大,其強度也相應(yīng)提高,且黏聚力提高更加明顯,而細(xì)顆粒土其顆粒尺寸對強度的影響較小。(2) 土水特征曲線用于描述非飽和土中含水量或飽和度與基質(zhì)吸力之間的關(guān)系,在非飽和土力學(xué)中非常重要。本文采用GEO-Experts 土水特征曲線壓力板儀對崩崗區(qū)花崗巖殘積土進(jìn)行大量的土水特征曲線實驗,測定了不同初始干密度、不同顆粒級配、不同石灰摻加量以及干濕循環(huán)作用下的重塑非飽土崩崗區(qū)花崗巖殘積土試樣的土水特征曲線。研究表明:初始干密度對土水特征曲線有影響明顯,土水特征曲線隨著干密度的增大明顯下移,當(dāng)基質(zhì)吸力較大時,有著相互聚攏的趨勢;當(dāng)干密度相同時,顆粒級配小的土樣的吸力更大;土水特征曲線也有隨著石灰含量的增加而下移的趨勢,表明其水穩(wěn)定性變好;在干濕循環(huán)作用下,土水特征曲線的脫濕曲線和吸濕曲線有顯著的滯回現(xiàn)象,滯回圈的面積隨著干密度的增大和干濕循環(huán)次數(shù)的增加而減小,摻入石灰后滯回圈的面積也變小。同時還進(jìn)行了顆粒級配和豎向應(yīng)力對土水特征曲線的影響研究,通過施加豎向應(yīng)力以模擬不同顆粒級配的土壤在受力狀態(tài),并獲得其相應(yīng)的土水特征曲線。在無豎向應(yīng)力時,不同顆粒級配土樣的土水特征曲線差別不大,但有豎向應(yīng)力時,不同顆粒級配土樣的土水特征曲線差別明顯,且有隨著豎向應(yīng)力增加而增大的趨勢。在低基質(zhì)吸力區(qū)豎向應(yīng)力對土水特征曲線的影響更為明顯,而在高基質(zhì)吸力區(qū)的影響則相對更小。根據(jù)試驗獲得的數(shù)據(jù)利用Fredlund Xing模型、Van Genuchten模型和Gardner模型三種土水特征曲線擬合模型對其進(jìn)行擬合,通過三種模型的擬合結(jié)果對比可知,VanGenuchten模型可以很好地描述和預(yù)測崩崗侵蝕區(qū)非飽和花崗巖殘積土的土水特征曲線。(3)考慮到巖土工程參數(shù)和計算模型存在不確定性,根據(jù)土水特征曲線預(yù)測的自身特點,建立基于貝葉斯更新的土水特征曲線預(yù)測框架,將利用現(xiàn)有兩種土水特征曲線預(yù)測模型Fredlund Xing模型和Van Genuchten模型與試驗實測信息相融合,采用貝葉期更新理論框架和前期觀測數(shù)據(jù)對理論計算模型中的計算參數(shù)更新,再利用更新后的參數(shù)對土水特征曲線進(jìn)行更為精確的預(yù)測,通過模型參數(shù)的不斷更新實現(xiàn)土水特征曲線動態(tài)預(yù)測。當(dāng)采用合理的測量誤差的標(biāo)準(zhǔn)差時,采用有限的實驗數(shù)據(jù)更新后預(yù)測的土水特征曲線精確度較高,通過貝葉斯更新和實驗方法結(jié)合方法為快速有效地預(yù)測土水特征曲線提供了一種析途徑。(4) 土水特征曲線擬合模型中存在多個似合參數(shù),各參數(shù)的值通過實驗方法獲得且具有不確定性。本文探索采用貝葉斯理論分析擬合參數(shù)的不確定性,將土水特征曲線擬合參數(shù)作為隨機變量,采用Fredlund Xing模型、Van Genuchten模型和Gardner模型三種模型以及花崗巖殘積土的土水特征曲線試驗數(shù)據(jù),以馬爾可夫鏈蒙特卡羅方法(MCMC方法)的延遲拒絕適應(yīng)性算法(DRAM算法)獲得模型參數(shù)后驗分布抽樣,獲得了不同置信區(qū)間的土水特征曲線及其對應(yīng)參數(shù)值,該方法可以有效地估計土水特征曲線模型的參數(shù),并獲得土水特征曲線的置信區(qū)間。(5) 土水特征曲線在邊坡的滲流和穩(wěn)定性分析中具有非常重要的作用,結(jié)合土水特征曲線的不確定性,研究了土水特征曲線的置信度對降雨入滲邊坡的滲流場和邊坡安全系數(shù)的影響,獲得非飽和土邊坡滲流場和穩(wěn)定性隨置信度的變化規(guī)律。不同置信度的土水特征曲線對邊坡滲流場影響較大,且孔隙水壓力隨降雨歷時變化最為明顯,孔隙水壓力隨降雨歷時的增長速率隨著土水特征曲線的置信度百分點的增加而增大;隨著置信度百分點的增加,降雨條件下的邊坡穩(wěn)定性在相應(yīng)減小。
[Abstract]:The erosion is the most serious type of soil erosion in the granite area of southern China, and the southern Jiangxi area is the heavy disaster area in the south of Jiangxi Province. The factors affecting the slope erosion are many aspects. Water is the most important external cause. The water content of the unsaturated soil slope is increased by the rainfall infiltration, thus the matrix suction in the soil is also related. The physical and mechanical properties of this kind of soil are greatly influenced by the water, and the characteristics of the unsaturated soil properties of this kind of soil can be provided for the study and prevention of the mechanism of the erosion of the landslides in the south of Jiangxi. In this paper, we take the granite residual soil as the research object, use the experimental instruments such as unsaturated soil three axis instrument and pressure plate instrument to study the characteristics of its strength and deformation and the measurement of soil water characteristic curve, carry out the study of soil water characteristic curve prediction based on Bayesian theory, and establish the effective preview of the soil water characteristic curve by using the finite data. At the same time, the uncertainty analysis of the parameters of the soil water characteristic curve model is carried out, the confidence interval of the soil water characteristic curve is obtained and applied to the slope stability analysis under the rainfall condition. (1) the strength and deformation characteristics of the unsaturated granite residual soil in the landslide area are discussed, and the remolded soil samples are controlled by the unsaturated soil three axis instrument. In the force consolidation drainage shear test, the effects of dry density, net confining pressure and matrix suction on the relationship of stress strain, strength and body variation are studied. The shear properties of unsaturated granite residual soil under the controlled suction condition are analyzed. The study shows that the stress-strain relationship depends on the combination of net confining pressure and matrix suction. The contribution of matrix suction to the strength of unsaturated soil shows that the matrix suction has a great influence on the cohesive force, and it has a linear growth trend, while the effect on the effective internal friction angle is smaller. The same is the control suction drainage shear test on the lime modified granite residual soil to study the strength and change of the lime content to the unsaturated soil. The influence of the shape characteristics is that the improved granite residual soil with ash ratio 0%, 4% and 8% is used respectively. At the same time, two kinds of particle size (1mm, 2mm) granite residual soil have been selected. The cohesive force and friction angle of lime improved soil increased with the increase of lime content, and the strength of the lime soil increased correspondingly, and the cohesiveness increased more clearly. The particle size of fine granular soil has little effect on the strength. (2) the soil water characteristic curve is used to describe the relationship between water content or saturation of unsaturated soil and matrix suction, which is very important in the mechanics of unsaturated soil. This paper uses the GEO-Experts soil water characteristic curve pressure plate instrument to carry out a large amount of soil in the granite residual soil in the landslide granite area. The water characteristic curves of different initial dry density, different grain gradation, different lime content and dry and wet cycle were used to remould the soil water characteristic curve of the granite residual soil specimen under the action of dry and wet cycle. The study shows that the initial dry density has obvious influence on the soil water characteristic curve, and the soil water characteristic curve is increasing with the dry density. When Daming is moved down, there is a tendency to gather together when the suction of the matrix is large; when the dry density is the same, the soil sample with small particle size is more suction; the soil water characteristic curve also moves down with the increase of lime content, indicating that the water stability becomes better, and the dehumidification curve and hygroscopic curve of the soil water characteristic curve under the action of dry and wet circulation. With the increase of dry density and the increase of dry and wet cycle times, the area of hysteresis loop decreases with the increase of dry density and the number of dry and wet cycles, and the effect of grain gradation and vertical stress on the soil water characteristic curve is also studied. The soil of different grain gradation is simulated by applying vertical stress. When there is no vertical stress, the soil water characteristic curves of different particle graded soil samples have little difference, but when there is vertical stress, the soil water characteristic curves of different grain grading soil samples are distinct, and the vertical stress increases with the vertical stress. The vertical stress in the low matrix suction area is the same. The influence of the soil water characteristic curve is more obvious, but the influence in the high matrix suction area is relatively smaller. According to the data obtained by the experiment, the Fredlund Xing model, the Van Genuchten model and the Gardner model are fitted to the fitting model of three soil water characteristic curves. The VanGenuchten model can be compared through the comparison of the fitting results of the model type. In order to describe and predict the soil water characteristic curve of the unsaturated granite residual soil in the avalanche erosion area. (3) considering the uncertainty of the geotechnical engineering parameters and the calculation model, according to the characteristics of the soil water characteristic curve predicted, the soil water characteristic curve prediction frame based on the Bayesian updating will be established, and the existing two kinds of soil water characteristics will be used. The line prediction model Fredlund Xing model and the Van Genuchten model are fused with the experimental data. The theoretical framework and the early observation data are used to update the calculation parameters in the theoretical calculation model, and the soil water characteristic curves are more accurately predicted by the updated parameters, and the model parameters are constantly updated. The dynamic prediction of soil water characteristic curve is realized. When the standard deviation of reasonable measurement error is adopted, the accuracy of the soil water characteristic curve predicted by the finite experimental data is higher, and a way of fast and effective prediction of soil water characteristic curve is provided by the combination of Bayesian updating and experimental method. (4) soil water characteristic curve There are multiple coincidence parameters in the fitting model, and the values of each parameter are obtained by the experimental method and have uncertainty. In this paper, the uncertainty of the fitting parameters is analyzed by the Bayesian theory, and the parameters of the soil water characteristic curve are taken as random variables, and the three models of Fredlund Xing model, Van Genuchten model and Gardner model are used. And the soil water characteristic curve test data of the granite residual soil, using the delayed rejection adaptive algorithm (DRAM algorithm) of the Markov Monte Carlo method (MCMC method) to obtain the model parameter posterior distribution sampling, obtained the soil water characteristic curve and its corresponding parameter values of different confidence intervals. This method can effectively estimate the soil water characteristic curve. The parameters of the line model and the confidence interval of the soil water characteristic curve are obtained. (5) the soil water characteristic curve plays a very important role in the seepage and stability analysis of the slope. Combining the uncertainty of the soil water characteristic curve, the influence of the confidence degree of the soil water characteristic curve on the seepage field and the slope safety factor of the rainfall infiltration slope is studied. The soil water characteristic curve of different reliability has great influence on the seepage field of the slope, and the pore water pressure is most obvious with the rainfall duration, and the growth rate of pore water pressure increases with the increase of the confidence degree of the soil water characteristic curve. With the increase of confidence level, the slope stability under rainfall condition decreases correspondingly.
【學(xué)位授予單位】：南昌大學(xué)
【學(xué)位級別】：博士
【學(xué)位授予年份】：2017
【分類號】：TU43

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本文編號：1967016