摘要
为研究深部煤层底板卸荷劣化破坏机理,开展了轴压不变卸围压、加轴压卸围压、卸轴压卸围压不同加卸载应力路径下的假三轴力学试验,分析并拟合了不同应力路径下岩石弹性模量、广义泊松比与围压的变化关系;构建了岩石断裂力学模型,分析了不同加卸载路径下,分支裂纹端部应力集中程度;从偏应力、能量、声发射事件等方面剖析了卸荷过程中岩石力学参数劣化机制。研究表明:①不同轴压加载方式下岩样的弹性模量劣化程度和泊松比变化幅度依次为加轴压>轴压保持不变>卸轴压;相同轴压不同围压卸载速率下,岩样的弹性模量劣化程度和泊松比变化幅度与卸荷速率呈正相关变化。②围压卸荷过程中,轴向加载或保持不变的应力路径相比于轴向卸载的应力路径,岩石积聚的能量增长幅度较大;在围压卸载至一定程度时,内部闭合的微裂隙和原生裂隙重新被打开,用于裂纹扩展的能量迅速增加,泊松比和弹性模量变化比例明显增大,声发射事件振铃数呈现出非线性增长的特点。③不同加卸载路径下,偏应力是诱发岩石失稳破坏的根本原因,偏应力增长越快,岩石弹性模量劣化程度和泊松比变化程度越明显。工作面附近处于压剪破坏区偏应力相对较大,岩体劣化程度相对较为严重,这与工作面底板突水事故多发生在工作面附近相一致。
In order to study the failure mechanism of deep coal seam floor under unloading,pseudo-triaxial mechanical tests were carried out under different loading and unloading stress paths.The relationship between rock elastic modulus,generalized Poisson ratio and confining pressure under different stress paths was analyzed and fitted.The rock fracture mechanics model was constructed,and the stress concentration at the end of the branch crack under different loading and unloading paths was analyzed.The deterioration mechanism of rock mechanical parameters during unloading was analyzed from the aspects of deviatoric stress,energy and acoustic emission events.①The research showed that the degree of deterioration of the elastic modulus of the sample and the change range of Poisson ratio under different axial compression loading methods were in the order of axial compression>axial compression remain unchanged>unloading axial pressure.Under the same axial pressure and different confining pressure unloading rates,the elastic modulus deterioration degree and Poisson ratio change of the sample were in a positive correlation with the unloading rate.②Compared with the increase of the deviator stress at the unloading point,it changed in a positive correlation with the deterioration degree of the elastic modulus of the rock sample and the change of Poisson's ratio.During the unloading process of the confining pressure,the energy accumulated in the path that the axial load or remain unchanged was larger than the stress path of axial unloading.When the confining pressure was unloaded to a certain extent,the internal closed micro-cracks and primary fissures were reopened,and the energy used for crack propagation increased rapidly,and the ratio of change to elastic modulus and the Poisson’s ratio increased significantly,and the number of acoustic emission event ringing showed a characteristic of non-linear growth.③Under different loading and unloading paths,the deviatoric stress was the fundamental cause of rock instability and
作者
张风达
张玉军
于秋鸽
ZHANG Fengda;ZHANG Yujun;YU Qiuge(Coal Mining and Designing Department,Tiandi Science and Technology Co.,Ltd,Beijing 100013,China;Coal Mining and Designing Branch,China Coal Research Institute,Beijing 100013,China;CCTEG Coal Mining Research Institute,Beijing 100013,China)
出处
《煤炭科学技术》
CAS
CSCD
北大核心
2022年第12期117-127,共11页
Coal Science and Technology
基金
国家自然科学基金资助项目(51704158)
天地科技股份有限公司开采事业部科技创新基金资助项目(KJ-2019-TDKCMS-02,KJ-2021-KCMS-06)。
关键词
岩石力学
断裂力学
加卸载
卸荷点
深部底板
卸荷劣化
rock machanics
fracture machanics
loading and unloading
unloading point
deep bottom plate
unloading degradation
