【摘要】：軟弱夾層的存在是引起順層邊坡失穩(wěn)破壞的關(guān)鍵性因素之一,而泥化夾層作為最常見的次生型軟弱夾層,抗剪強度指標(biāo)極低,常常是導(dǎo)致斜坡失穩(wěn)的主控因素。泥化夾層的核心問題是強度問題,然而,在具體的工程應(yīng)用當(dāng)中存在一個普遍的問題,即當(dāng)工程實際中層間泥化夾層厚度較薄時,難以通過室內(nèi)常規(guī)直剪試驗或三軸壓縮試驗來獲取其強度指標(biāo)。為解決這一實際工程問題,論文擬從泥化夾層細(xì)觀結(jié)構(gòu)出發(fā),結(jié)合室內(nèi)單軸壓縮試驗及數(shù)字散斑變形測量技術(shù),獲取其壓縮變形特性及破壞特征,然后采用離散元方法建立泥化夾層數(shù)值模型,研究其應(yīng)變軟化本構(gòu)特征,并對其強度進行預(yù)測。具體的研究內(nèi)容包括以下幾個方面： (1)通過SEM電鏡掃描對泥化夾層原狀樣進行細(xì)觀掃描,結(jié)合閾值分割技術(shù)對掃描圖片進行二值化處理,然后利用matlab統(tǒng)計分析對其細(xì)觀結(jié)構(gòu)進行量化,主要獲取了后續(xù)離散元建模過程中所需的泥化夾層孔隙率。 (2)采用數(shù)字散斑成像技監(jiān)測記錄泥化夾層單軸壓縮試驗過程中的變形破壞機制,并利用應(yīng)變破壞準(zhǔn)則和土力學(xué)中土的極限平衡條件研究獲得泥化夾層的剪切強度特征。 (3)利用PFC顆粒流程序語言,建立泥化夾層離散元模型,分別對數(shù)值單軸壓縮試驗及直接剪切試驗進行了參數(shù)敏感性分析,主要研究了顆粒剛度、顆粒間摩擦系數(shù)、接觸粘結(jié)強度、豎向應(yīng)力、加載速率等因素對數(shù)值試樣應(yīng)力應(yīng)變本構(gòu)關(guān)系的影響。結(jié)合室內(nèi)單軸壓縮試驗的結(jié)果對泥化夾層顆粒流模型中的細(xì)觀力學(xué)參數(shù)進行了標(biāo)定,得到比較能真實反映泥化夾層真實狀態(tài)和力學(xué)性能的數(shù)值模型。 (4)利用數(shù)值直接剪切試驗和反復(fù)剪切試驗對泥化夾層剪切破壞細(xì)觀機制及其應(yīng)變軟化特性進行較為深入的研究,并對其峰殘強度參數(shù)進行預(yù)測。 隨著西部大開發(fā)步伐的大力推進和西部山區(qū)公路的大量修建,泥化夾層可能導(dǎo)致的路基邊坡穩(wěn)定性問題日益突出,本論文研究旨在為實際工程中的邊坡穩(wěn)定性評價提供參數(shù)依據(jù)。
[Abstract]:The existence of weak intercalation is one of the key factors leading to the instability of bedding slope. As the most common secondary weak interlayer, the shear strength index is very low, which is often the main controlling factor of slope instability. The core problem of mud interlayer is strength problem. However, there is a general problem in concrete engineering application, that is, when the thickness of clay interlayer is thin in engineering practice, It is difficult to obtain the strength index by conventional direct shear test or triaxial compression test. In order to solve this practical engineering problem, this paper intends to obtain the compression deformation characteristics and failure characteristics of the mudded sandwich mesoscopic structure, combined with indoor uniaxial compression test and digital speckle deformation measurement technology. Then the numerical model of mudded intercalation is established by discrete element method. The constitutive characteristics of strain softening are studied and its strength is predicted. The specific research contents include the following aspects: (1) Meso-scanning of mudded interlayer raw samples by SEM scanning electron microscope, and binarization processing of scanned images with threshold segmentation technology, Then the meso-structure was quantified by matlab statistical analysis, and the porosity of mudded intercalation was obtained in the process of subsequent discrete element modeling. (2) the deformation and failure mechanism of mudded interlayer during uniaxial compression test is recorded by digital speckle imaging, and the shear strength characteristics of mudded interlayer are obtained by using strain failure criterion and limit equilibrium condition of soil in soil mechanics. (3) based on the PFC program language, a discrete element model of mudded intercalation is established, and the parameter sensitivity of numerical uniaxial compression test and direct shear test are analyzed respectively. The stiffness of particles and the friction coefficient between particles are studied. The influence of contact bond strength, vertical stress and loading rate on the stress-strain constitutive relationship of numerical specimens. Combined with the results of laboratory uniaxial compression tests, the meso-mechanical parameters of the mudded interlayer particle flow model are calibrated, and a numerical model which can truly reflect the true state and mechanical properties of the mudded interlayer is obtained. (4) using numerical direct shear test and repeated shear test, the meso-mechanism of shear failure and strain softening characteristics of mudded intercalation were studied, and the peak and residual strength parameters were predicted. With the rapid development of the western region and the construction of a large number of highways in the western mountainous areas, the stability of the subgrade slope caused by the mud intercalation may become increasingly prominent. The purpose of this paper is to provide parameter basis for slope stability evaluation in practical engineering.
【學(xué)位授予單位】：西南石油大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2015
【分類號】：TU43

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