Abstract: In South China, the geosynthetic reinforced retaining wall using high liquid limit soil as backfill is applied widely. Because of climate change, the suction between unsaturated high liquid limit clay and geotextile is altering; thus influencing the interface shear characteristic. So the interface shear characteristic between unsaturated high clay and geotextile considering suction change should be studied deeply. In this paper, a series of direct shear tests are performed using ZFY-1A direct shear apparatus to investigate the shearing resistance properties of high plasticity clay-geotextile interface under suction cycle. Results of experiment indicate that the peak shear strength of the soil-geotextile interface increases with the net normal stress. Interface strength increases at first and then reduces with the increase of cycling times, interface strength is lowest through 3 times of the dry-wet circulation. And interface strength is reduced in general. , , , and increase and then decrease with the increase of cycling times. increases with the cycling times and net normal stress. decreases with net normal stress, and increases then decreases with the increase of cycling times. Finally, the interface strength formula under different suction conditions is obtained through the logarithmic fitting.

Key words: high liquid limit of clay, matrix suction, geotextiles, direct shear test, suction cycle