Geosynthetics are extensively used in building bases and liner systems in landfills. In engi-neering practices, geosynthetics are usually paved on top of compacted soils, forming soil-geosynthetic interfaces. Large scale direct shear tests are widely adopted to investigate the shear behavior of the inter-face. In existing researches, the relative displacement of the shear boxes is usually taken as the relative displacement between soil and geosynthetics, which is different from the real scenario. The reason is that soil undergoes a certain extent of creep deformation during the shearing process. In the present study, a new direct shear testing technology, including a newly designed apparatus and corresponding testing method, was developed to measure the shear behavior of the soil-geosynthetic interfaces between soft clay and textured geomembrane. A soil-grabbing apparatus was designed to accurately acquire the dis-placement of soil at the soil-geosynthetic interface. A series of interface direct shear tests were performed with large scale specimen (600×200 mm), under a constant normal stress of 100 kPa, with a shear dis-placement of 70 mm and shear rate of 1 mm/min. The results indicate that the developed apparatus is a powerful tool to investigate the shear behavior of the soil-geosynthetic interface.
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