摘要
在煤矿井巷冻结法施工工程中,地下工程结构的破坏常始于受拉区域,因此开展冻融岩石的抗拉强度劣化机理研究有一定意义。对不同冻融循环作用下的砂岩进行巴西劈裂实时声发射监测,从细观层次探讨了冻融作用对砂岩劈裂损伤过程的影响。结果表明:冻融作用引起砂岩物理性质改变,抗拉强度降低;冻融砂岩劈裂损伤在时间域具有连续演进的特征,损伤发育速度在关键时刻有突变,可通过振铃计数峰值进行定性评判;在冻融循环5次前后,损伤发育速度突变,表现为声发射事件频率与能量值突增;随着冻融循环次数的增加,声发射累计能量出现时间提前,持续时长缩短,岩样提前进入弹性变形阶段,呈现由脆性破坏向延性破坏转换的趋势;高能声发射事件多发于损伤快速扩展期,可作为损伤传导和加剧的重要参照;振铃计数和累计能量同步大幅度激增至更高数量级是冻融砂岩破坏失稳时间域的前兆信息;声发射b值先降后升,表明砂岩破坏模式由内部大裂隙破坏转变为持续小裂隙破坏。依据损伤力学理论,基于累计振铃计数所建立的损伤变量能较好反映冻融砂岩抗拉损伤演化过程各阶段及损伤特征。
In the construction of coal mine tunnels with freezing method,the destruction of underground engineering structures often begins in the tension area.It is of significance to study the tensile strength and deterioration mechanism of frozen-thawed rocks.Real-time acoustic emission monitoring of Brazilian splitting of sandstone under different freeze-thaw cycles was carried out.The influence of freeze-thaw cycles on the fracture damage process of sandstone was discussed at a meso level.The experimental results have shown that the physical properties of sandstone change due to freezing and thawing cycles,and the tensile strength is reduced.The splitting damage of freeze-thaw sandstone evolves continuously in the time domain,and the damage development speed has abrupt changes at critical moments.The peak ringing count can characterize the size of freeze-thaw damage,and qualitatively judge the degree of rock sample damage.Before 5 freeze-thaw cycles,the damage development rate changes suddenly,which is manifested as a sudden increase in the frequency and energy of acoustic emission events.As the number of freeze-thaw cycles increases,the accumulative acoustic emission energy appears earlier and the duration shortens.The rock sample enters the elastic deformation stage in advance,and the duration is shortened;the rock sample changes from brittle failure to ductile failure.High-energy acoustic emission events often occur during the rapid expansion period of damage,which can be used as an important reference for damage conduction and aggravation.The ringing count and accumulated energy simultaneously surge to a higher order of magnitude,which can be used as precursor information in the time domain of freeze-thaw sandstone failure and instability.The b-value of acoustic emission drops first and then rises,indicating that the failure mode of sandstone has changed from large internal fractures to continuous small fractures.The damage variable established based on the cumulative ringing count can better reflect the evolution process stage of the tensile damage of freeze-thaw sandstone.
作者
刘慧
蔺江昊
杨更社
贠烨辉
张慧梅
梁博
张尧
LIU Hui;LIN Jianghao;YANG Gengshe;YUN Yehui;ZHANG Huimei;LIANG Bo;ZHANG Yao(College of Civil and Architectural Engineering,Xi'an University of Science and Technology,Xi'an,Shaanxi 710054,China;School of Science,Xi'an University of Science and Technology,Xi'an,Shaanxi 710054,China)
出处
《采矿与安全工程学报》
EI
CSCD
北大核心
2021年第4期830-839,共10页
Journal of Mining & Safety Engineering
基金
国家自然科学基金项目(41702339,51774231,41971095,11872299)
国家重点研发计划项目(2018YFC0808705)
陕西省自然科学基础研究计划项目(2018JQ4026,2020JZ-53)
陕西省重点研发计划项目(2017ZDXM-SF-082)。
关键词
冻融循环
细粒砂岩
巴西劈裂
声发射
抗拉损伤
freeze-thaw cycle
fine-grained sandstone
brazilian splitting
AE
tensile damage
