砂岩、花岗岩阻尼特性及机制的试验研究

发布时间：2018-04-09 06:34

本文选题：阻尼比　切入点：阻尼系数　出处：《西安理工大学》2017年硕士论文

【摘要】：岩石阻尼参数是岩体工程抗震设计的重要参数,是工程进行抗震分析、安全评价的重要依据,但目前的岩石试验规程中尚无确定岩石阻尼参数相关内容。本文对砂岩、花岗岩进行循环荷载试验、外部激振试验,研究阻尼参数和动弹性模量随频率、应变幅值、应力水平变化规律,为岩石动力试验规程制定做一些基础性的研究工作。主要研究成果如下:(1)从能量守恒角度出发,基于粘弹性理论,提出了压-压循环荷载作用下岩石阻尼比的计算公式。(2)高频范围内,阻尼比随频率增加而减小,低频范围内,阻尼比随频率增大而增大。推测阻尼比随频率变化存在阈值,当频率小于阈值,阻尼比随频率增大而增大,当频率大于阈值,阻尼比随频率增大而减小。阻尼系数与阻尼比变化规律相反。利用物理模型确定了砂岩、花岗岩阻尼比随频率变化的阈值分别为2.23Hz、4.08Hz。(3)在高频条件下,阻尼比与阻尼系数随应变幅值增加而增加,阻尼比随应变幅值变化可分为三阶段:前期增长阶段、稳定阶段、后期增长阶段,阻尼系数阶段性不明显。低频时,阻尼比与阻尼系数随应变幅值增大而增大。(4)阻尼比随应力水平增加而减小,阻尼系数随应力水平增加而增大。应力水平提升使砂岩胶结物质软石膏被压密,花岗岩微裂隙被压实,减少了耗能源,粘性机制启动难度加大,表现为阻尼比下降,阻尼系数增大。(5)动弹性模量随频率与应力水平增加而增加,随应变幅值增加而减小。(6)砂岩、花岗岩阻尼参数与动弹性模量随频率、应变幅值及应力水平变化规律一致。但砂岩阻尼比对应力水平敏感,花岗岩阻尼参数及动弹性模量对应变幅值敏感,反映出碎屑岩类与结晶岩类成因及结构不同对阻尼参数与动弹性模量的影响。
[Abstract]:Rock damping parameter is an important parameter in seismic design of rock mass engineering. It is an important basis for seismic analysis and safety evaluation of rock mass engineering. However, there is no relevant content of rock damping parameter in rock test rules at present.In this paper, cyclic load tests and external vibration tests are carried out on sandstone and granite to study the variation of damping parameters and dynamic elastic modulus with frequency, strain amplitude and stress level.Do some basic research work for rock dynamic test rules.The main research results are as follows: (1) from the point of view of energy conservation and based on viscoelastic theory, a formula for calculating the damping ratio of rock under compression-compression cyclic load is proposed. In the range of high frequency, the damping ratio decreases with the increase of frequency, and in the range of low frequency.The damping ratio increases with increasing frequency.It is inferred that there is a threshold when the frequency is less than the threshold, and the damping ratio increases with the increase of the frequency, and decreases with the increase of the frequency when the frequency is greater than the threshold.The change of damping coefficient is opposite to that of damping ratio.It is determined by physical model that the threshold value of granite damping ratio with frequency is 2.23 Hz ~ 4.08 Hz 路m ~ (3). At high frequency, the damping ratio and damping coefficient increase with the increase of strain amplitude.The change of damping ratio with strain amplitude can be divided into three stages: early growth stage, stable stage, late growth stage, and damping coefficient stage is not obvious.At low frequency, the damping ratio and damping coefficient increase with the increase of strain amplitude. The damping ratio decreases with the increase of stress level, and the damping coefficient increases with the increase of stress level.The increase of stress level compacts the sandstone cemented material, compacts the micro-cracks of granite, reduces the energy consumption, increases the difficulty of starting viscous mechanism, and shows the decrease of damping ratio.The dynamic elastic modulus increases with the increase of frequency and stress level, and decreases with the increase of strain amplitude. The variation of damping parameter and dynamic elastic modulus of granite is consistent with frequency, strain amplitude and stress level.However, the damping ratio of sandstone is sensitive to stress level, and the damping parameters and dynamic elastic modulus of granite are sensitive to the strain amplitude, which reflects the influence of the origin and structure of clastic rocks and crystalline rocks on the damping parameters and dynamic elastic modulus.
【学位授予单位】：西安理工大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TU45

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