【摘要】：細觀力學(xué)特性是粗粒土力學(xué)特性的主要研究內(nèi)容之一。目前，試驗及測試技術(shù)都無法獲取其細觀力學(xué)參數(shù)，粗粒土宏觀力學(xué)特性內(nèi)在作用機制不能得到很好的揭示。PFC作為離散元方法的一種，是細觀分析的主要手段之一。在PFC三軸數(shù)值模擬試驗中，建立既高效又反應(yīng)室內(nèi)試樣顆粒級配的數(shù)值模型是三軸數(shù)值模擬的基礎(chǔ)，選擇各細觀參數(shù)值的調(diào)節(jié)順序及調(diào)節(jié)程度是提高三軸數(shù)值模擬效率的關(guān)鍵，采用不同的細觀分析方法揭示粗粒土宏觀力學(xué)特性內(nèi)在機制是三軸數(shù)值模擬試驗的最終目的。因此，，本文基于室內(nèi)三軸試驗研究成果，開展PFC三軸數(shù)值試驗研究，提出了高效數(shù)值建模方法和新的細觀分析方法，分析細觀參數(shù)對宏觀力學(xué)特性的影響，并進行了各細觀參數(shù)力學(xué)及變形敏感性排序。本文主要研究工作及成果如下： 1）基于已有的室內(nèi)大型三軸試驗數(shù)據(jù)，自編程序，建立PFC3D三軸數(shù)值試驗?zāi)Ｐ汀?2）首次提出采用加權(quán)平均數(shù)方法生成模型中的顆粒，避免粒徑較小的顆粒數(shù)目龐大導(dǎo)致的計算效率的降低。同時根據(jù)顆粒粒徑的加權(quán)平均數(shù)生成方法，能夠很好的得到三軸數(shù)值試驗應(yīng)力應(yīng)變曲線結(jié)果。 3）從細觀角度分析不同圍壓下剪切過程中顆粒位移場和顆粒轉(zhuǎn)動速度場的變化規(guī)律，并根據(jù)其變化情況分析室內(nèi)三軸試驗宏觀力學(xué)特性現(xiàn)象的細觀本質(zhì)。 4）首次將測量模型運用到三軸數(shù)值試驗?zāi)Ｐ椭校ㄟ^自編測量模型程序，采用133個測量球體對試樣內(nèi)部裂隙分布進行檢測，根據(jù)量球環(huán)內(nèi)的顆粒配位數(shù)、孔隙度以及體應(yīng)變在剪切過程中的變化規(guī)律分析剪切面在三軸模型中的空間分布，得到三軸數(shù)值試驗的空間剪切面。 5）進行了各細觀參數(shù)對粗粒土強度以及變形的敏感性影響分析，其中包括：孔隙度、顆粒配位數(shù)、顆粒法向剛度與切向剛度之比（kn/ks）、顆粒粒徑分布、剪切速率以及摩擦系數(shù)等細觀參數(shù)。得出各細觀參數(shù)對粗粒土峰值強度的敏感性排序為：kn/ks摩擦系數(shù)剪切速率顆粒粒徑分布孔隙度配位數(shù)。
[Abstract]:Meso-mechanical properties are one of the main contents of mechanical properties of coarse grained soils. At present, testing and testing techniques can not obtain its meso-mechanical parameters, and the internal mechanism of macroscopic mechanical properties of coarse grained soil can not be well revealed. PFC, as a discrete element method, is one of the main means of meso-analysis. In the PFC triaxial numerical simulation test, it is the foundation of triaxial numerical simulation to establish a numerical model that is both efficient and responsive to indoor sample particle gradation. The key to improve the efficiency of triaxial numerical simulation is to select the adjusting order and degree of each meso-parameter value. The ultimate purpose of triaxial numerical simulation test is to reveal the internal mechanism of macroscopic mechanical properties of coarse grained soil by using different meso-analytical methods. Therefore, based on the research results of indoor triaxial test, the PFC triaxial numerical test is carried out, and an efficient numerical modeling method and a new mesoscopic analysis method are proposed to analyze the influence of mesoscopic parameters on the macroscopic mechanical properties. The order of mechanical parameters and deformation sensitivity is also given. The main work and results of this paper are as follows: 1) based on the data of large scale triaxial test, a program is developed. The PFC3D triaxial numerical test model is established. 2) the weighted average method is used to generate the particles in the model for the first time to avoid the reduction of computational efficiency caused by the large number of smaller particles. At the same time, according to the weighted average of particle size, The results of stress and strain curves of triaxial numerical tests can be obtained well. 3) the variation law of particle displacement field and particle rotation velocity field during shearing under different confining pressures are analyzed from the view of meso. According to its variation, the meso nature of macroscopic mechanical characteristics of indoor triaxial test is analyzed. 4) the measurement model is first applied to the triaxial numerical test model. The fracture distribution in the specimen was measured by 133 measuring spheres. The spatial distribution of the shear surface in the triaxial model was analyzed according to the variation of particle coordination number, porosity and volume strain in the measuring sphere ring during the shear process. The spatial shear plane of triaxial numerical test was obtained. 5) the effects of various meso-parameters on the strength and deformation sensitivity of coarse grained soil were analyzed, including porosity, particle coordination number, The ratio of normal stiffness to tangential stiffness (kn/ks), particle size distribution, shear rate, friction coefficient and so on. The sensitivity of the meso-parameters to the peak strength of coarse-grained soil is in the order of 1: KN / KS friction coefficient shear rate particle size distribution porosity coordination number.
【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】：2015
【分類號】：TU411

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