基于时间效应的富水泥质板岩隧道围岩膨胀本构模型研究

A time-dependent constitutive model of the water-rich argillaceous slate surrounding a tunnel

针对原有三维膨胀本构模型的局限性,以富水泥质板岩隧道围岩的膨胀问题为出发点,采用侧向约束下的膨胀特性试验,修正了泥质板岩侧向约束下的轴向膨胀率与吸水时间的关系及膨胀过程中的一维本构关系;基于金尼克条件,考虑整个膨胀过程以及最大和最小膨胀应力对膨胀本构方程的贡献,以最大体积膨胀率对应的时间为临界时间,分段描述泥质板岩基于时间效应的三维膨胀本构模型。研究结果表明:泥质板岩在膨胀过程中轴向应力和膨胀率之间呈负对数函数关系;当吸水时间小于或等于临界时间时,侧向约束下的轴向膨胀率与吸水时间之间的关系式服从指数函数,体积膨胀率服从含时间效应的三维膨胀本构模型;当吸水时间大于临界时间时,侧向约束下的轴向膨胀率不再随时间变化,等于侧向约束下的最终轴向膨胀率,且体积膨胀率不再服从本构模型,等于定值(最大体积膨胀率)。研究成果可为解决富水软岩隧道围岩的膨胀问题提供理论参考。

To overcome the limitation of the existing three-dimensional swelling constitutive model, the swelling tests under lateral restraint condition are conducted on the swelling rock sampled from a water-rich argillaceous slate tunnel. On the basis of the experimental results, the relationship between the axial swelling ratio under lateral restraint and the water absorption time is revised, and a one-dimensional constitutive equation for swelling is developed. Based on the Kinnick conditions, the overall swelling process is described with considering the contribution of the maximum and minimum swelling stress to the swelling behavior. With the time of the maximum volume swelling rate being the critical time, a time-dependent 3-D swelling constitutive model of argillaceous slate is developed, which can be expressed stage by stage. The results show that the relationship of axial stress and axial swelling rate can be expressed as a negative logarithmic function. When the water absorption time is less than or equal to the critical time, the relationship between the lateral restraint swelling ratio and the water absorption time follows an exponential law, and the volume swelling rate obeys the three-dimensional swelling constitutive model with considering the time effect. When the water absorption time exceeds the critical time, the axial swelling ratio under lateral restraints no longer changes with time, but remains to be the final axial swelling rate under lateral restraint. Moreover, the volume swelling rate no longer obeys the constitutive model, but becomes the constant value （the maximum volume expansion rate）. These results can provide a theoretical reference for solving the surrounding rock swelling problem of water-rich soft rock tunnel.