【摘要】：隨著我國(guó)西部大開發(fā)的進(jìn)一步推進(jìn),大量巖土工程將在西部寒區(qū)進(jìn)行,為確保工程的安全性,有必要研究巖石的凍融力學(xué)特性。本文從實(shí)際寒區(qū)巖體工程出發(fā),采用理論與試驗(yàn)相結(jié)合的方法,較為系統(tǒng)地研究了凍融與荷載作用下砂巖的損傷特性�，F(xiàn)場(chǎng)選取整塊新鮮的大塊砂巖,加工成標(biāo)準(zhǔn)圓柱形試件,分別對(duì)其進(jìn)行飽水后的凍融循環(huán)試驗(yàn),并在凍融循環(huán)次數(shù)為0次,5次,10次,20次以及40次時(shí),進(jìn)行圍壓為0MPa,2MPa,4MPa以及6MPa的三軸壓縮試驗(yàn)。觀察試驗(yàn)現(xiàn)象,得出砂巖主要破壞形式;分析討論試驗(yàn)結(jié)果,得到砂巖在凍融循環(huán)和荷載作用下的力學(xué)參數(shù),以及砂巖強(qiáng)度及變形特性隨凍融循環(huán)次數(shù)和圍壓的變化規(guī)律。應(yīng)用連續(xù)損傷力學(xué)理論及推廣后的應(yīng)變等價(jià)原理,基于巖石D-P準(zhǔn)則,分別采用Weibull分布和Poisson分布描述砂巖微元強(qiáng)度的隨機(jī)特性,建立砂巖的損傷模型,通過(guò)試驗(yàn)數(shù)據(jù)驗(yàn)證了模型的合理性。分析比較得出兩種分布在描述砂巖壓縮破壞過(guò)程中沒有顯著的差異,但由于采用Poisson分布所得參數(shù)表達(dá)式較為復(fù)雜,因此實(shí)用性不強(qiáng)。對(duì)砂巖損傷本構(gòu)模型進(jìn)行了修正,修正后的模型能夠較好地反映砂巖應(yīng)力應(yīng)變曲線峰后段的變化情況,更精準(zhǔn)的描述了砂巖殘余強(qiáng)度;分析討論了模型參數(shù)的物理意義;將砂巖損傷模型由常規(guī)三軸應(yīng)力狀態(tài)推廣到真三軸應(yīng)力狀態(tài),從而能夠從理論上描述中間主應(yīng)力對(duì)砂巖強(qiáng)度及力學(xué)特性的影響。建立了真三軸應(yīng)力狀態(tài)下,凍融砂巖的損傷模型,分析其損傷力學(xué)特性,并利用砂巖凍融循環(huán)和三軸壓縮試驗(yàn)數(shù)據(jù),驗(yàn)證了損傷模型的合理性。當(dāng)圍壓一定時(shí),凍融循環(huán)與荷載對(duì)砂巖造成的總損傷隨著凍融循環(huán)次數(shù)的增大而增加,同時(shí)凍融循環(huán)作用使得砂巖的塑性增強(qiáng),脆性減弱;當(dāng)凍融循環(huán)次數(shù)一定時(shí),砂巖的總損傷隨著圍壓的增大而減小,且塑性特性明顯增強(qiáng)。
[Abstract]:With the further development of the western part of China, a large number of geotechnical engineering will be carried out in the cold regions of the western part of China. In order to ensure the safety of the project, it is necessary to study the freeze-thaw mechanical properties of rocks. In this paper, the damage characteristics of sandstone under the action of freeze-thaw and load are studied systematically by the method of combining theory with test, starting from the actual rock mass engineering in cold area. The whole piece of fresh large sandstone was processed into standard cylindrical specimen, and the freezing and thawing cycle test was carried out after saturated. When the cycles of freezing and thawing were 0 times, 5 times, 10 times, 20 times and 40 times, the confining pressure was 0 MPA, 2 MPA, and 2 MPA, respectively, when the cycles of freezing and thawing were 0 times, 5 times, 10 times, 20 times and 40 times, respectively. Triaxial compression test of 4MPa and 6MPa. The main failure forms of sandstone are obtained by observing the experimental phenomena, and the mechanical parameters of sandstone under freeze-thaw cycle and load are obtained by analyzing and discussing the test results, as well as the variation of strength and deformation characteristics of sandstone with the times of freezing-thawing cycle and confining pressure. Based on the theory of continuous damage mechanics and the generalized strain equivalence principle, the damage model of sandstone is established by using the Weibull distribution and the Poisson distribution to describe the random characteristics of the strength of sandstone microelement, based on the Dp criterion of rock. The rationality of the model is verified by the experimental data. The analysis and comparison show that there is no significant difference between the two distributions in describing the process of sandstone compression failure, but the expression of parameters obtained by using Poisson distribution is rather complex, so the practicability is not strong. The damage constitutive model of sandstone is modified. The modified model can better reflect the change of the stress-strain curve of sandstone, and describe the residual strength of sandstone more accurately, and the physical significance of the model parameters is discussed, and the parameters of the model are analyzed and discussed, and the physical significance of the parameters of the model is analyzed and discussed. The damage model of sandstone is extended from the conventional triaxial stress state to the true triaxial stress state, so that the influence of intermediate principal stress on the strength and mechanical properties of sandstone can be described theoretically. The damage model of frozen-thawed sandstone under true triaxial stress is established and its damage mechanical characteristics are analyzed. The rationality of the damage model is verified by using the freezing-thawing cycle and triaxial compression test data of sandstone. When the confining pressure is constant, the total damage caused by freeze-thaw cycle and load to sandstone increases with the increase of freezing-thawing cycle times, meanwhile, the plasticity of sandstone is enhanced and the brittleness of sandstone is weakened by freezing-thawing cycle. When the number of freeze-thaw cycles is constant, the total damage of sandstone decreases with the increase of confining pressure, and the plastic properties are obviously enhanced.
【學(xué)位授予單位】：西安科技大學(xué)
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2015
【分類號(hào)】：TU45

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