三轴压缩下含瓦斯煤样蠕变特性试验研究

 介绍自主研制的含瓦斯煤岩三轴蠕变试验系统。利用三轴蠕变试验系统对含瓦斯煤样进行一系列三轴蠕变试验，得到不同蠕变载荷、不同围压和不同瓦斯压力条件下的蠕变结果。试验结果显示，蠕变载荷、围压和瓦斯压力是影响含瓦斯煤样蠕变特性的重要因素；含瓦斯煤样的蠕变行为可以表现出衰减蠕变和非衰减蠕变2种形态；减速蠕变阶段是弹性后效的结果；稳态蠕变速率受蠕变载荷、围压和瓦斯压力的影响，并且随蠕变载荷和瓦斯压力的增大而增大，随围压的增大而减小；加速蠕变阶段是含瓦斯煤样破坏的开始。基于试验结果，详细分析含瓦斯煤样的减速蠕变和稳态蠕变阶段的蠕变速率，给出能分别描述减速和稳态蠕变阶段蠕变速率的幂函数和指数函数方程。利用规范化方法建立能反映稳态蠕变速率、蠕变载荷、围压和瓦斯压力之间关系的数学方程，利用该方程可以很容易地预测各种应力状态下稳态蠕变速率的大小。

TEST STUDY OF CREEP PROPERTIES OF GAS-BEARING COAL SPECIMENS UNDER TRIAXIAL COMPRESSION

A self-developed triaxial creep system of gas-bearing coal is introduced firstly. A series of triaxial creep tests on gas- bearing coal specimens are carried out by using the creep system,and results of the creep tests under different creep stresses,confining pressures and gas pressures are obtained. The results show that creep stress,confining pressure and gas pressure are the important factors affecting the creep properties of the coal specimens;the creep behaviors of the specimens can be split into two parts mainly:one is the attenuating creep,the other is the non-attenuating creep. Decelerating creep stage is caused by elastic aftereffect;by the actions of creep stress,confining pressure and gas pressure during creep tests,steady-state creep rate increases with the increasing of confining stress and gas pressure,and decreases with the increasing of confining pressure. Accelerating creep stage marks the starting of the failure of coal specimens. Based on the creep results,the creep rates at decelerating creep stage and steady-state creep stage are analyzed in detail;and in addition,a power function and an exponent function are proposed which can effectively describe the creep rates at transient creep stage and steady-state creep stage respectively. By a normalized method,a mathematical equation is constructed which can model the relationship among the steady-state creep rate,creep stress,confining pressure and gas pressure. And using this equation,the value of steady-state creep rate under various stress conditions can be estimated easily.