In the repair work for aged small earth dams, geosynthetic clay liners (GCLs) are used as impermeable materials in addition to cohesive soils. However, the design standard for small earth dams using the GCLs is not established since there are few studies on their mechanical characteristics. In this study, in order to examine the mechanical characteristics of GCLs laid in embankments during earthquakes, cyclic direct shear tests were conducted on the internal bentonite layer of needle-punched GCL. The tests were performed under the conditions of the normal stress of 25 kPa considering the low confining pressure in embankments, and the amplitude of shear displacement of 0.5, 1.0, 3.0, and 5.0 mm. It was found that the shear strength decreased with the number of cycles on the tests, due to the rupture of needle-punching and pullout of it from geotextiles. Moreover, the results revealed that the amount of decrease in the shear strength increased, as the amplitude became larger.
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