Abstract: A series of tests were performed in this study to examine shear strength characteristics of the rockfill samples of argillaceous siltstone under loading cycles of coupled wetting-cooling and drying-heating, using a new weathering test apparatus developed by our laboratory. The test results show that the shear strength is decreased under lower vertical load because particle degradation is dominant while it is increased under higher vertical load because rockfill compaction is dominant. In the rockfill dam engineering, the weathering of rockfill could generally cause shallow landslide.