用西原模型描述双重孔隙-裂隙介质的流变特性，在理论上给出了其流变参数及强度指标的确定方法，建立了瞬弹-黏弹-黏塑性平面有限元求解格式和研制了相应的计算程序。针对一个矩形地下洞室围岩为裂隙岩体和完整岩体的两种工况进行数值分析，对比了围岩中的位移、应力及塑性区。其结果显示：相比于单一介质的情况，双重介质因其变形模量、凝聚力和内摩擦角减小，故洞室围岩中随时发展的位移和塑性区有明显的增长，两种工况的围岩应力分布亦存在较大的不同，特别是双重介质围岩中最大主应力 和最小主应力 的差值较大，因此，提高了围岩破坏的可能性。

Using Nishihara model to describe the rheological characteristics of dual-pore-fracture media, a method is theoretically presented to determine the rheological parameters and strength indices of the media. The plane finite element scheme for solving the transient elastic-viscoelastic-viscoplastic problems is built, and the corresponding calculation program is developed. Aiming at the two conditions of surrounding rock mass from a rectangular underground cavern, in which the first rock mass is fractured by two sets of joints (a dual medium) and the second one is intact (a single medium); the displacements, stresses and plastic zones in the surrounding rock masses are analysed and compared numerically. The results show that when compared with the case of single medium, the deformation modulus, cohesion and internal friction angle of the dual medium decrease, so the corresponding displacements and plastic zones in the surrounding rock mass develop with time elapsing obviously. And there is a greater difference between the stress distributions of these two cases, especially the difference between the maximum principal stress and the minor principal stress in the surrounding rock mass, which is larger for the case of dual medium. Therefore, the possibility of rock mass failure is increased.