岩-煤组合体试样变形场与能量演化特征试验研究

Experimental study on deformation field and energy evolution characteristics of rock-coal composite samples

采用数字散斑应变测量系统进行灰岩-煤组合体试样单轴压缩变形破坏演化试验,分析组合体试样变形局部化带和能量演化特征,揭示其渐进破坏机制。组合体试样变形局部化带演化主要与其内部原生裂纹起裂、扩展有关,变形局部化带首先出现在原生裂纹区域,沿最大主应力方向发育扩展,煤样内变形局部化带发育扩展相对较快,变形局部化带交汇、贯通导致组合体试样整体破坏失稳。变形局部化带位移错动量演化主要经历微变化、线性缓慢增长、非线性加速增长3个阶段,与轴向应力变化基本相对应,峰后变形局部化带快速扩展贯通,位移错动量非线性加速增长。外界输入能量主要被煤样变形破坏所消耗,煤样首先发生渐进破坏而释放能量,交界面处灰岩、煤样由协同变形转为非协同变形;煤样破坏诱发灰岩回弹变形并释放弹性能,部分弹性能作用于煤样而加剧其破坏,煤样发生拉-剪混合破坏;煤样内裂纹扩展传播至灰岩内,并与灰岩内裂纹贯通,导致其拉伸破坏。

The digital speckle strain measurement system was adopted to conduct uniaxial compression deformation and failure evolution tests on limestone-coal composite samples.The evolution characteristics of the deformation localization zone and energy of the composite samples were analyzed and the progressive failure mechanism was revealed.Mainly related to the internal initiation and propagation of primary cracks in the limestone-coal composite,the deformation localization zones first appeared around the primary cracks and then developed and expanded along the maximum principal stress direction.The deformation localization zones within the coal samples developed and expanded relatively rapidly.The intersection and penetration of deformation localization zones led to the overall failure and instability of the composite samples.The displacement dislocations of deformation localization zones mainly experienced three stages:Micro-change stage,linear slow growth stage,and nonlinear accelerated growth stage,roughly corresponding to the variations of axial stress.After the peak stress point,the deformation localization zones expanded and penetrated rapidly and the displacement dislocations increased nonlinearly.The external input energy was mainly consumed by the deformation and failure of coal samples,which released energy due to the progressive failure.At the same time,the limestone and coal samples at the interface changed from cooperative deformation to non-cooperative deformation.The failure of coal samples induced the rebound deformation of limestone and the release of elastic properties within it,part of which acted on the coal samples to aggravate their failure,resulting in the tensile-shear failure.The cracks in the coal samples propagated into the limestone and penetrated with the cracks in it,leading to the tensile failure of the limestone.