Temperature dependence of frictional healing of Westerly granite: Experimental observations and numerical simulations
Temperature dependence of frictional healing of Westerly granite: Experimental observations and numerical simulations
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DOI：
10.1029/2012gc004241
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发表时间：
2013-03
期刊：
影响因子：
3.7
通讯作者：
E. K. Mitchell;Y. Fialko;Kevin M. Brown
中科院分区：
文献类型：
--
作者：
E. K. Mitchell;Y. Fialko;Kevin M. Brown
温度被认为对岩石的摩擦特性具有重要的控制作用，然而高温下随时间变化的岩石摩擦的实验观测量相当有限。在这项研究中，我们在20°C和550°C之间的环境温度下，使用直接剪切装置，在一系列滑动-保持-滑动实验中研究了西风花岗岩的摩擦愈合。我们观察到，在室温下的摩擦系数的增加与保持时间的对数成比例的速率与以前的研究结果相一致。对于给定的保持时间，摩擦系数随温度线性增加，但温度对静摩擦随保持时间的变化率几乎没有影响。我们使用数值模型来研究粗糙表面之间的真实的接触面积随时间的增加是否可以解释所观察到的摩擦愈合。该模型结合了分形几何和温度依赖的粘弹塑性流变学。我们探讨了几个候选流变学，已提出的稳态蠕变岩石在高应力和温度。没有一个测试的法律可以提供一个协议之间观察到的和建模的愈合行为给定的材料性能报告的体积蠕变实验。通过修改参数，可以实现与实验数据的可接受拟合。特别是，为了使幂律流变学对数据提供合理的拟合，应力指数需要大于40。替代机制包括随时间变化的凿痕压实和接触粗糙体之间的结合强度增加。
Temperature is believed to have an important control on frictional properties of rocks, yet the amount of experimental observations of time‐dependent rock friction at high temperatures is rather limited. In this study, we investigated frictional healing of Westerly granite in a series of slide‐hold‐slide experiments using a direct shear apparatus at ambient temperatures between 20°C and 550°C. We observed that at room temperature coefficient of friction increases in proportion to the logarithm of hold time at a rate consistent with findings of previous studies. For a given hold time, the coefficient of friction linearly increases with temperature, but temperature has little effect on the rate of change in static friction with hold time. We used a numerical model to investigate whether time‐dependent increases in real contact area between rough surfaces could account for the observed frictional healing. The model incorporates fractal geometry and temperature‐dependent viscoelasoplastic rheology. We explored several candidate rheologies that have been proposed for steady state creep of rocks at high stresses and temperatures. None of the tested laws could provide an agreement between the observed and modeled healing behavior given material properties reported in the bulk creep experiments. An acceptable fit to the experimental data could be achieved with modified parameters. In particular, for the power‐law rheology to provide a reasonable fit to the data, the stress exponent needs to be greater than 40. Alternative mechanisms include time‐dependent gouge compaction and increases in bond strength between contacting asperities.