FRICTIONAL PROPERTIES OF SEDIMENTARY ROCKS AND NATURAL FAULT GOUGE FROM LONGMENSHAN FAULT ZONE AND THEIR IMPLICATIONS
(1. State Key Laboratory of Earthquake Dynamics，Institute of Geology，China Earthquake Administration，Beijing 100029，China；2. High Pressure and Temperature Laboratory，Faculty of Geosciences，Utrecht University，Utrecht 3508 TA，The Netherlands)
Abstract：This paper reports friction experiments performed on samples collected from the earthquake-hit region of the Longmenshan fault zone(LFZ). The materials tested consisted of simulated gouges prepared from intact clay-rich mudstone and sandstone，a calcite limestone，and a natural fault gouge from a trenched， surface rupture cutting the mudstone and sandstone. The clay-rich samples， including the natural fault gouge，were dominated by illite and quartz. In the experiments，1 mm thick gouge layers were sheared between saw-cut driver blocks，using a triaxial testing machine at conditions corresponding to 2 km depth in the LFZ. Temperature was varied from 25 ℃ to 150 ℃ and，to investigate the velocity dependence of friction，the shear displacement rate between 1.22 and 0.122 ?m/s was stepped. The results show that the natural fault gouge was more illite-rich and much weaker than the protolith mudstone and sandstone，and showed a steady-state friction coefficient of 0.4 compared with 0.6 for the latter. The limestone fault gouge displayed values of 0.6–0.7. All samples，except the limestone，showed stable，velocity-strengthening slip. The limestone showed velocity-strengthening at 25 ℃－50 ℃，but quasi-static oscillations at 100 ℃－150 ℃ along with velocity-weakening behavior at 150 ℃. The result is applied to discuss the role of the sedimentary rocks studied during events such as the Wenchuan earthquake；and it is argued that the clay-rich sediments of the region may have a damping effect upon ruptures propagating from depth；whereas the limestone may accelerate propagation，producing significant stress drops.
何昌荣1，VERBERNE B A1，2，SPIERS C J2. 龙门山断裂带沉积岩和天然断层泥的摩擦滑动性质与启示[J]. 岩石力学与工程学报, 2011, 30(1): 113-131.
HE Changrong1，VERBERNE B A1，2，SPIERS C J2. FRICTIONAL PROPERTIES OF SEDIMENTARY ROCKS AND NATURAL FAULT GOUGE FROM LONGMENSHAN FAULT ZONE AND THEIR IMPLICATIONS. , 2011, 30(1): 113-131.
2011, Vol. 30 
