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峰前峰后循环加卸载对砂岩动力特性的影响

Effect of Cyclic Loading and Unloading on Dynamic Characteristics of Sandstone before and after Peak Load

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  • 国家科技期刊平台
  • NETL
  • NSTL
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为深入分析砂岩峰前和峰后不同阶段的动力特性规律,开展单轴分级循环加卸载试验,综合分析下限应力对砂岩峰前峰后不同加卸载阶段的表观弹性模量、滞回圈面积、阻尼比、阻尼系数及动弹性模量等相关动力参数的影响.研究结果表明:①岩样在峰后因内部损伤加深和累积,相同下限应力下滞回曲线位于峰前右侧,且应变量增幅和最大应变增幅均随下限应力的增加而逐渐减小,说明峰后岩样虽然强度已达到极限状态,但只要岩石未完全破坏失稳,其致密性仍可以在高应力条件下的循环加卸载中得到增强.②砂岩在峰前峰后循环加卸载下的变化过程,可以通过表观弹性模量曲线斜率a值的变化得以体现,低下限应力循环加卸载试验中,致密性增强系数a1＞致密性劣化系数a2,斜率a均为正值,轴向应力对岩石整体的压密作用明显强于劣化损伤作用;随着下限应力升高,a2的降低速率高于a1的升高速率,a值逐渐减小甚至变为负值,说明轴向应力对岩石整体的压密作用逐渐弱于劣化损伤作用.③4组不同下限应力条件下,岩样峰后的滞回圈面积、阻尼比、阻尼系数均高于峰前状态,而动弹性模量低于峰前状态,说明岩样在峰后循环加卸载过程中内部劣化损伤程度高于峰前.
To comprehensively examine the dynamic characteristics of sandstone at different stages before and after the peak,we conducted uniaxial graded cyclic loading and unloading tests.These tests aimed to analyze the impact of the lower limit stress on various parameters,including the apparent elastic modulus,hysteretic loop area,damp-ing ratio,damping coefficient,and dynamic elastic modulus of sandstone during the loading and unloading stages.The research findings indicate the following:1)Due to the aggravation and accumulation of internal damage after peak,the hysteretic curve lies on the right side before the peak at the same lower limit stress.With an increase in the lower limit stress,the increments in strain and maximum strain gradually decrease.This suggests that despite limit strength has been reached after peak,cyclic loading and unloading under high-stress conditions can enhance the compactness of post-peak rock samples,as long as the rock remains intact and stable.2)The changes in sand-stone under cyclic loading and unloading before and after peak load can be observed through variations in the slop-ing(a)of apparent elastic modulus curve.At small lower limit stress,the coefficient of compactness enhancement(a1)is greater than the coefficient of compactness degradation(a2);additionally,the slope a is positive,indica-ting that the compressive effect of axial stress on rock mass is significantly stronger than the effect of deterioration damage.As the lower limit stress rises,the rate of decrease in a2 is higher than that of a1,suggesting that the com-pressive effect of axial stress gradually weakens compared to that of deterioration damage.3)Under four different lower limit stress conditions,the hysteretic loop area,damping ratio,and damping coefficient are higher after the peak than before,while the dynamic elastic modulus after peak is lower than before.These findings suggest that the degree of internal deterioration damage in rock samples during cyclic loading and unloading after the peak is higher than that before the peak.

sandstonebefore and after peakcyclic loading and unloadingapparent elastic modulusminimum stress limitdynamic characteristics

王瑞红、贾敬茹、骆浩、危灿、张健锋、贾依行

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三峡大学三峡库区地质灾害教育部重点实验室,湖北宜昌 443002

兰州理工大学土木工程学院,兰州 730000

砂岩 峰前峰后 循环加卸载 表观弹性模量 下限应力 动力特性

国家自然科学基金面上项目湖北省自然科学基金杰出青年项目三峡库区地质灾害教育部重点实验室(三峡大学)开放基金项目

519791512021CFA0902020KDZ07

2024

10.11988/ckyyb.20221257

长江科学院院报
长江科学院

长江科学院院报

CSTPCD北大核心
影响因子：0.618
ISSN：1001-5485
年,卷(期)：2024.41(3)
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