循环荷载作用下煤变形及渗透特性的试验研究

 利用自主研发的含瓦斯煤岩热流固耦合三轴伺服渗流装置，以型煤试件为研究对象，进行不同温度条件下循环荷载试验，研究循环荷载作用下煤变形及渗透特性。研究结果表明：(1) 随温度的升高，煤循环形成的滞回曲线所围成的面积逐渐减小。在单个循环曲线中，加、卸载阶段的主应力差、渗透率与轴向应变曲线呈现“X”状；在同一循环周期下，轴向应变与渗透率随温度的升高逐渐减小；在同一温度下，轴向变形随循环次数的增加逐渐增大。(2) 随温度的升高，加载阶段曲线斜率逐渐增加，累计变形总量降低，即提高了不可逆过程的发展速率。(3) 在各温度条件下，加载阶段应变及渗透率在整个循环过程中的变化均不明显。卸载阶段应变及渗透率在第1次循环期间变化较大，但从第2次循环开始，应变随循环次数的增加趋于平缓。在相同循环次数下，体积应变随温度的升高逐渐增大，渗透率逐渐减小。

EXPERIMENTAL STUDY OF DEFORMATION AND SEEPAGE CHARACTERISTICS OF COAL UNDER CYCLIC LOADING

Based on the self-developed triaxial servo-controlled seepage equipment for thermal-hydro- mechanical coupling of coal containing methane，the cyclic loading test is performed on coal samples under different temperatures. The results are shown as follows：(1) The area surrounded by hysteretic curve reduces gradually with temperature increase. In a single hysteresis curve，the relation curves between principal stress difference，permeability and axial strain present X-shape. In the same cycle，the axial strain and permeability decrease gradually with temperature increase. The axial deformation increases as the number of cycles increases in same temperature condition. (2) As temperature increases，the slope of curve in loading stage increases，the cumulative deformation reduces，which means the development rate of the irreversible process has been improved. (3) In different temperature conditions，the changes of strain and permeability in loading stage are not obvious during the entire cycle. In unloading stage，the strain and permeability change significantly in the first cycle，and strain curve begins to stabilize with increase of the number of cycles. When the number of cycles is the same in different temperature conditions，the volumetric strain increases gradually and the permeability decreases with increase of temperature.