Frictional strength of ground dolerite gouge at a wide range of slip rates
Frictional strength of ground dolerite gouge at a wide range of slip rates
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DOI：
10.1002/2015jb012013
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发表时间：
2016-04
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通讯作者：
Jun-ichi Wada;K. Kanagawa;H. Kitajima;M. Takahashi;A. Inoue;T. Hirose;J. Ando;H. Noda
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作者：
Jun-ichi Wada;K. Kanagawa;H. Kitajima;M. Takahashi;A. Inoue;T. Hirose;J. Ando;H. Noda
我们在地面白云石凿槽上进行了一系列的旋转剪切摩擦实验，在室温和湿度下，在2 MPa的正应力下，在20µm/s到1.3 m/s的恒定等效滑移率（Veqs）范围内，吸附的水分随研磨时间（tgr）的增加而增加。它们的摩擦强度随Veq和tgr有三种不同的变化方式，这取决于Veq和泥温(T)。在Veq≤1.3 cm/s时，T不超过80℃，稳态摩擦系数（μss）在0.59 ~ 0.80之间。μss随Veq变化不大，而在一定Veq下μss随tgr有系统地增加，这可能是由于沟槽的吸湿强化所致。在Veq = 4 cm/s时，温度超过100℃，不同时间的热蚀槽脱水后的μss值大致相同（0.60 ~ 0.66）。当Veq≥13 cm/s时，温度达到160 ~ 500℃，μs随Veq急剧下降，在Veq = 1.3 m/s时，μs随温度的升高而有系统地下降。在这些快速的速度下，凿槽的脱水可能发生得太快，以至于水蒸气无法完全从凿槽层中逸出。因此，在更快的Veq下，更快的脱水可能导致更大的孔隙压力增加和更低的摩擦强度。此外，由于较长tgr周期的沟槽含有较多的吸附水分，因此由于孔隙压力的较大增加而变得较弱，因此摩擦强度的降低幅度较大。
We conducted a series of rotary‐shear friction experiments on ground dolerite gouges, in which the amount of adsorbed moisture increases with grinding time (tgr), at room temperature and humidity, a normal stress of 2 MPa, and constant equivalent slip rates (Veqs) ranging from 20 µm/s to 1.3 m/s. Their frictional strength changed with Veq and tgr in three different ways depending on Veq and the gouge temperature (T). At Veq ≤ 1.3 cm/s, T did not exceed 80°C, and the steady state friction coefficient (μss) ranged from 0.59 to 0.80. μss changes little with Veq, while μss at a given Veq systematically increases with tgr probably due to moisture‐adsorbed strengthening of gouges. At Veq = 4 cm/s, T exceeded 100°C, and dehydration of gouges resulted in roughly the same μss values (0.60–0.66) among gouges with different periods of tgr. At Veq ≥ 13 cm/s, T reached 160–500°C, and μss dramatically decreases with Veq to 0.08–0.26 at Veq = 1.3 m/s, while μss at a given Veq systematically decreases with tgr. At these fast Veqs, dehydration of gouges likely occurred too fast for water vapor to completely escape out from the gouge layer. Therefore, faster dehydration at faster Veq possibly resulted in a larger pore pressure increase and lower frictional strength. In addition, because gouges with longer periods of tgr contain larger amounts of adsorbed moisture, they became weaker due to larger increases in pore pressure and hence larger amounts of reduction in frictional strength.