基于热力学原理的土体动力模型阈值应变研究
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摘要
基于热力学基本定律,建立了塑性中心移动为直线和骨架曲线两种情况下Hardin-Drnevich模型的能量耗散函数表达式,并与具体试验相结合讨论了不同动应变水平下反滤料、细堆石料、粗堆石料的能量耗散机制。发现筑坝堆石类无黏性材料的动力特性存在2个应变阈值,定义为第1和第2阈值应变,其对应的割线模量与最大动剪模量之比分别为大于0.97及0.5~0.8之间。从工程应用的角度看,若土体动应变小于第1阈值应变,则可直接采用最大动剪模量及常阻尼比进行土体动力分析;第2阈值应变与传统意义上以孔隙水压力升高或体积变化为标准定义的门槛应变相当。
Based on the fundamental law of thermodynamics the energy dissipation function expression of Hardin-Drnevich model for soil is established.The formula is used to combine with experimental result to discuss the energy dissipation mechanism of different materials for rockfill dam.It is found that the dynamic characteristics of materials of rockfill dam have two thresholds of strain which may define as the first threshold and the second threshold.The study result shows that the ratios of secant modulus to maximum dynamic shear modulus for these two strain thresholds are higher than 0.97 and 0.5~0.8 respectively.From the view point of engineering practice,if dynamic strain of soil is smaller than the first strain threshold,the maximum dynamic shear modulus and constant damping ratio can be used to analyze the dynamic characteristics of soils.The second strain threshold is equivalent to that defined by increase of traditional pore pressure and volume change.
引文
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