轴向加载速率对原煤力学和渗透特性的影响

    Effect of axial loading rate on mechanical and permeability properties of raw coal

    • 摘要: 采用煤岩流变仪对原煤进行了不同轴向加载速率下的常规三轴力学渗流试验,运用体积扩容应力、峰值应力、弹性模量和变形模量作为原煤的力学指标,发现试验所用原煤与典型的脆性岩石的规律相同,原煤作为非线性弹性材料体,4种力学指标均随着轴向加载速率的增大而增大;加载过程煤样能量耗散可分为峰前和峰后阶段,峰前阶段绝大部分吸收的能量转化为可释放弹性应变能,耗散应变能增加的速率较缓,峰后阶段弹性应变能急剧下降,大量释放并转化为耗散应变能;同时应力峰值处的总能量随轴向加载速率的增大而增大;渗透率-应变曲线总体呈现“V”字形的变化特征;在全应力-应变过程中,煤岩渗透率与轴向应变之间满足二次多项式函数关系。

       

      Abstract: The coal-rock rheometer was used to carry out conventional triaxial mechanical seepage experiments on raw coal under different axial loading rates in this paper. Volume expansion stress, peak stress, elastic modulus and deformation modulus were used as mechanical indexes of raw coal. It was found that the law of raw coal used in the experiment was the same as that of typical brittle rock. The mechanical properties increase with the increase of axial loading rate. During the loading process, the energy dissipation of coal samples can be divided into pre-peak stage and post peak stage. Most of the energy absorbed in the pre-peak stage is transformed into releasable elastic strain energy, and the rate of dissipative strain energy increasing is relatively slow. In the post peak stage, the elastic strain energy decreases sharply and a large amount is released and converted into dissipative strain energy. At the same time, the total energy at the peak stress increases with the increase of axial loading rate. The permeability strain curve generally presents a “V” shape. In the whole stress-strain process, the relationship between coal permeability and axial strain satisfies quadratic polynomial function.

       

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