冻融循环中低应力水平加卸载作用下砂岩动力特性研究

发布时间：2018-03-21 13:42

本文选题：冻融循环　切入点：阻尼比　出处：《岩土力学》2017年09期 　论文类型：期刊论文

【摘要】：采用不会造成较大附加损伤的近似无损低应力水平加、卸载的方法,开展了考虑时间效应的冻融循环作用试验。在试验成本受限的情况下大幅度地降低了试验所需的岩样数。较常规试验方法,在试验岩样数不变的前提下,无需因岩样的离散性而进行主观地筛选数据,从而使得有效数据增多。随着冻融循环周期数增加,岩样表面孔隙及微裂隙不断扩大并出现软化层,裂纹加深,颗粒脱落程度加剧,发生片落、剥蚀,水分向岩石内部迁移,冻融损伤程度由内向外逐渐加深,并研发滴定技术定量标定了这种层进式损伤。进一步分析不同冻融循环周期数下岩样在不同上限应力循环作用下的动力响应变化规律。研究显示,阻尼比、阻尼系数及动泊松比均与冻融循环周期数呈线性递增的关系,动弹性模量与冻融循环周期数呈线性递减的关系;阻尼比、动泊松比均与幅值应力呈线性递减的关系,动弹性模量与幅值应力呈线性递增的关系。给出了阻尼比、动泊松比、阻尼系数、动弹性模量相互之间的定量关系,可通过一种参数的变化规律,预测另一种参数的变化趋势。在有限的试验条件、试验次数下,可有效地精简试验所需检测的参数。幅值应力越大,加、卸载转换时岩样弹性变形响应越迅速,不可逆变形越小,在同一幅值应力的情况下所吸收的能量减少。随着冻融循环周期数的增加,循环加、卸载前岩样的斜坡加载段逐渐变长,应力-应变曲线斜率逐渐变小;循环加、卸载后,不同加、卸载幅值应力下的每个周期中首次达到应力上限时岩样的轴向应变与冻融周期数呈线性关系,说明在冻融循环作用下,岩样孔隙率逐渐变大,密实程度降低,岩样有逐步软化的趋势。当幅值应力较大时,岩样的塑性累积量与冻融周期数呈指数型关系加速递增;当幅值应力较小时,岩样的塑性累积量与冻融周期数呈线性关系匀速递增;说明幅值应力会带来显著的加速劣化效果。
[Abstract]:The method of near lossless low stress level loading and unloading without causing greater additional damage is used. The freeze-thaw cycle test considering time effect is carried out. The number of rock samples required for the test is greatly reduced under the condition of limited test cost. Compared with the conventional test method, when the number of test samples remains unchanged, There is no need to screen the data subjectively because of the dispersion of rock samples, so as to increase the effective data. With the increase of cycles of freeze-thaw cycles, the pores and micro-cracks on the surface of rock samples expand and soften layers appear, and the cracks deepen. The degree of particle shedding intensifies, the debris falls, denudates, the water migrates to the rock, and the degree of freeze-thaw damage deepens gradually from inside to outside. The titration technique was developed to quantitatively calibrate the damage, and the dynamic response of rock samples under different cycles of freezing and thawing cycles under different upper limit stress cycles was further analyzed. Damping coefficient and dynamic Poisson's ratio are linearly increasing with the number of cycles of freeze-thaw cycle, dynamic modulus of elasticity is linearly decreasing with the number of cycles of freeze-thaw cycle, damping ratio and dynamic Poisson's ratio are linearly decreasing with amplitude stress. The relationship between dynamic elastic modulus and amplitude stress is linearly increasing. The quantitative relationship between damping ratio, dynamic Poisson's ratio, damping coefficient and dynamic elastic modulus is given. The change trend of another parameter is forecasted. Under limited test conditions and times of test, the parameters needed for testing can be effectively simplified. The larger the amplitude stress, the faster the elastic deformation response of rock sample during unloading conversion. The smaller the irreversible deformation, the less the energy absorbed under the same amplitude stress. With the increase of the cycle number of freeze-thaw cycle, the loading section of the slope of rock sample before unloading gradually becomes longer and the slope of stress-strain curve becomes smaller. After cyclic loading and unloading, the axial strain of rock sample is linearly related to the number of freezing and thawing cycles when the unloading amplitude stress reaches the stress limit for the first time in each cycle, which indicates that the porosity of rock sample increases gradually under the action of freezing and thawing cycle. When the amplitude stress is large, the plastic accumulation of rock samples increases exponentially with the number of freezing and thawing cycles, while the amplitude stress is small. There is a linear relationship between the plastic accumulation of rock samples and the number of freeze-thaw cycles, which indicates that amplitude stress will bring about significant accelerated deterioration effect.
【作者单位】：三峡大学三峡库区地质灾害教育部重点试验室;
【基金】：国家自然科学基金项目(No.51439003,No.51579138,No.51479102) 国家科技支撑计划项目(No.2015BAB07B08) 成都理工大学地质灾害防治与地质环境保护国家重点试验室开放基金项(No.SKLGP2016K023) 2016年三峡大学研究生科研创新基金项目(No.SDYC2016025)~~
【分类号】：TU45

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