分阶段卸荷过程中构造煤的力学特征及能量演化分析

发布时间：2018-08-17 15:33

【摘要】：采用恒定轴压以不同卸荷速率分阶段卸围压的方式,分别对初始围压不同的三组煤样进行卸荷试验,然后对比分析了构造煤常规三轴加载和分阶段卸荷试验的应力-应变曲线特征,并从能量演化的角度分析了分阶段卸荷过程中煤样的能量变化规律。试验结果表明,构造煤分阶段卸围压试验的力学强度和变形能力明显小于常规三轴加载试验。分阶段卸荷过程中构造煤的偏应力和应变变化均呈现明显的阶梯状。在卸荷段,围压对试件的变形起到了限制作用,围压越大,应变增量越小、卸荷段越多;卸荷速率通过改变围压卸荷量影响应变变化,但相同卸荷速率时,围压越大应变增量越小;在恒压段,试件的应变变化呈现蠕变特征,通过数据拟合得到了其叠加开尔文体的蠕变方程。分阶段卸围压过程中,围压卸荷诱发弹性应变能持续释放,煤样吸收的总能量不断增加,其转化的耗散能也不断增大;围压卸荷速率越大,弹性应变能释放越快,耗散能变化率也越大,煤样强度衰减也更快;并且相同卸荷速率条件下,围压越小弹性应变能变化率也较小。
[Abstract]:Three groups of coal samples with different initial confining pressures were unloaded with constant axial pressure and different unloading rates. Then the characteristics of stress-strain curves of conventional triaxial loading and staged unloading tests of tectonic coal are compared and analyzed from the point of view of energy evolution. The test results show that the mechanical strength and deformation capacity of structural coal are obviously lower than that of conventional triaxial loading test. The deformation stress and strain of the tectonic coal show obvious ladder shape during the stage unloading. In the unloading section, the confining pressure limits the deformation of the specimen. The larger the confining pressure, the smaller the strain increment, the more the unloading section, the more the unloading rate affects the strain change by changing the confining pressure unloading amount, but at the same unloading rate, The strain increment of the specimen is smaller with the increase of confining pressure and the creep equation of the superimposed Kelvin body is obtained by fitting the data. In the process of unloading the confining pressure, the elastic strain energy is released continuously, the total energy absorbed by the coal sample increases, and the dissipation energy of the transformation increases, and the faster the unloading rate of the confining pressure is, the faster the elastic strain energy is released, the higher the unloading rate of the confining pressure is, the faster the elastic strain energy is released. The larger the rate of dissipation energy change, the faster the strength attenuation of coal sample is, and the smaller the confining pressure is, the smaller the elastic strain energy change rate is at the same unloading rate.
【作者单位】：重庆大学资源及环境科学学院;重庆大学煤矿灾害动力学与控制国家重点实验室;
【基金】：高等学校博士学科点专项科研基金资助项目(20130191130003) 重庆市研究生科研创新项目国家自然科学基金青年基金资助项目(51204216)
【分类号】：TD713;TQ531.4

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