高应力下原煤三轴卸荷力学特性研究  

STUDY OF MECHANICAL PROPERTIES OF RAW COAL UNDER HIGH STRESS WITH TRIAXIAL UNLOADING

作　　者：刘泉声[1] 刘恺德[1,2] 卢兴利[1] 朱杰兵[3] 

机构地区：[1]中国科学院武汉岩土力学研究所岩土力学与工程国家重点实验室,湖北武汉430071 [2]中煤科工集团西安研究院有限公司,陕西西安710054 [3]长江科学院水利部岩土力学与工程重点实验室,湖北武汉430010

出　　处：《岩石力学与工程学报》2014年第A02期3429-3438,共10页Chinese Journal of Rock Mechanics and Engineering

基　　金：国家自然科学基金资助项目(41130742);中国科学院知识创新工程重要方向项目(kzcx2–yw–152)

摘　　要：基于取自淮南矿区-780 m标高B10煤层的原煤,进行高应力下不等量卸围压和轴压的原煤卸荷试验,并与同围压下的常规三轴试验结果进行对比分析,研究卸荷条件下原煤的变形、强度、参数及破坏特征。研究结果表明：（1）从卸荷点起,偏应力–轴向应变曲线即突变＂上仰＂,斜率升高;但与常三轴曲线相比,卸荷峰值轴向应变显然减小,屈服进程明显缩短,峰后脆性破坏特征显著。（2）偏应力–侧向应变曲线从卸荷点开始突变＂下跌＂,斜率降低,峰值侧向应变明显小于常三轴;且峰后破坏前应力跌落较慢,3变化较大,而常三轴则跌落迅速,3变化较小。（3）偏应力–体积应变曲线从卸荷点起即反转左拐,呈现明显扩容,且在峰值点附近扩容最为剧烈。而常三轴曲线则除在较低围压下表现出扩容特征外,高围压下始终向右延展,呈现不断收缩状态。（4）卸荷时变形模量E始终降低,而损伤因子D和泊松比则一直增大;且三者变化趋势均在峰前平缓,峰后逐渐加剧。随初始围压的增加,E,D,总体上均呈升高趋势。（5）卸荷煤样以剪切破坏为主,破断角θ=20°-32°,且随初始围压的增加,θ以抛物线趋势升高;初始围压相同时,角度小于常三轴。（6）卸荷条件下煤岩抗剪强度参数c值明显小于常三轴,而值则变化不大。Based on the raw coal from B10 seam of-780 m in Huainan coal mine,unloading tests under high stress were carried out in the style of non-uniform velocity of unloading confining pressure and axial pressure synchronously,and the test results were compared with that of conventional triaxial experiments under the same confining pressure. The deformation,strength,parameters and failure characteristics of the raw coal under unloading were studied. The results show that：（1） From the unloading point,the deviatoric stress-axial strain curves pitch up abruptly,and its gradient increases. But compared with conventional triaxial curve,peak axial strain under unloading condition decreases apparently,yield process is obviously shorten and post-peak brittle failure characteristics is significant.（2） From the unloading point,the deviatoric stress- lateral strain curves fall abruptly,and its gradient decreases. The peak lateral strain is smaller than that of conventional triaxial curves. Before post-peak destroying,the stress drops slowly,and 3 changes greatly. While that of conventional triaxial curves fall rapidly,and 3 changes small.（3） From unloading point,the deviatoric stress-volume strain curves reverse left instantly,presenting the features of obvious dilatancy. And in the interval near peak point,the dilatancy is the strongest. However,except the conventional triaxial curves show dilatancy characteristics under low confining pressure conditions,the curves always extended right under high confining pressure,and presenting a continuous shrinkage state.（4） In the process of unloading,the deformation modulus E always reduces,and the damage factor D and Poissons ratio μ always increase. And the three change trend are gentle before peak,gradually increase after peak. Moreover,the E,D and μ all increase in general with the increase of initial confining pressure.（5） The failure modes of unloading coal samples are mainly shear failure,and rupture angle is in the range of 20°–32°,which increases in para

关 键 词：岩石力学 高应力 原煤 卸荷 变形特征 强度特征 破坏机制 力学参数 

分 类 号：TU45[建筑科学—岩土工程]