循环荷载下粉砂岩孔裂隙扩展及卸载破坏特征  

Pore fracture propagation and unloading failure characteristics of siltite under cyclic loads

作　　者：刘向御 柴肇云[2] 刘绪 杨泽前 辛子朋 LIU Xiangyu;CHAI Zhaoyun;LIU Xu;YANG Zeqian;XIN Zipeng(College of Mining Engineering,Taiyuan University of Technology,Taiyuan 030024,China;Key Laboratory of In⁃Situ Property⁃Improving Mining of Ministry of Education,Taiyuan University of Technology,Taiyuan 030024,China)

机构地区：[1]太原理工大学矿业工程学院,山西太原030024 [2]太原理工大学原位改性采矿教育部重点实验室,山西太原030024

出　　处：《煤炭学报》2022年第S01期77-89,共13页Journal of China Coal Society

基　　金：国家自然科学基金资助项目(51974193,51674173);山西省重点研发计划(国合)资助项目(201803D421078)

摘　　要：为揭示循环荷载下地下工程围岩体孔裂隙扩展及破坏机制,借助于单轴压缩和CT扫描,开展了粉砂岩的等幅循环、逐级一次循环加卸载试验。研究了循环荷载下粉砂岩应力-应变曲线、孔裂隙扩展及破坏阶段裂缝产状、规模等演化规律。结果表明:2种循环荷载作用下,粉砂岩孔隙率均呈先减小后增加的总趋势,且致裂循环的孔隙率均发生突变,具有瞬时破裂特征;等幅循环加卸载下,岩石破坏发生在第25次循环加载段,主要依据应变差、累积应变差及其一阶导数将岩样破坏段裂缝扩展细分为裂缝萌生、裂缝扩展和加速破坏等3个阶段;逐级一次循环加卸载下,岩石破坏发生在第4次循环卸载强度低于峰值载荷1.04 MPa时,呈现出小幅振荡破坏特征,主要依据单峰波动应力振幅、频率、应变差、累积应变差及其一阶导数将岩样破坏段裂缝扩展细分为裂缝萌生、裂缝快速扩展、裂缝扩展亚稳态、裂缝再生和加速破坏等5个阶段。按应力-应变曲线形态,小幅振荡破坏可细分为往复式、滞回环式波动,应力振幅、波动频率特征分析可见清晰的应力调整过程。岩样原始孔裂隙分布状态对其致裂部位及破坏形式起主控作用。2种循环荷载作用下,岩样破裂均以剪切破裂为主,并次生了张性破裂。卸载段回弹和扩容效应是出现小幅振荡破坏的主要原因。In order to reveal the pore fracture propagation and failure mechanism of underground engineering surrounding rock under cyclic loads,the uniaxial compression and CT scanning were used to carry out constant amplitude cyclic loading and unloading and stepwise linear cyclic loading and unloading tests on siltite.The stress-strain curves of siltite,the propagation of pores and fractures,and the occurrence and scale of fractures in the failure stage are studied under cyclic loading and unloading.The results show that the siltite porosity decreases first and then increases under two kinds of cyclic loads,and the porosity of fracture cycle changes suddenly,which has the characteristics of instantaneous fracture.Under the constant amplitude cyclic loading and unloading,rock failure occurs in the 25 th cyclic loading section,and according to the strain difference,the cumulative strain difference and its first derivative mainly,the fracture propagation in the failure stage of rock samples is subdivided into three stages:fracture initiation,fracture propagation,and accelerated failure.Under the stepwise lineal cyclic loading and unloading,the rock failure occurs in the 4 th cyclic unloading section,and presents the characteristics of low-amplitude oscillation failure when the strength is lower than the peak load of 1.04 MPa.According to the unimodal fluctuant stress amplitude,frequency,strain difference,cumulative strain difference and its first derivative mainly,the fracture propagation in the failure stage of rock samples is subdivided into five stages:fracture initiation,rapid fracture propagation,metastable fracture propagation,fracture regeneration,and accelerated failure.According to the form of stress-strain curve,the low-amplitude oscillation failure can be subdivided into a reciprocating cyclic wave and a hysteretic cyclic wave,and the analysis of stress amplitude and wave frequency shows a clear stress adjustment process.The distribution of original pores and fractures of the rock samples plays a major role in co

关 键 词：循环加卸载 粉砂岩 孔裂隙 扩展规律 小幅振荡 破坏阶段 

分 类 号：TD315[矿业工程—矿井建设]