A Novel Multifunctional Ring Shear Apparatus for Investigating the Interface Strength Characteristics of Liner Systems

A novel multifunctional ring shear apparatus is introduced in this paper, which is developed for investigating the interface strength characteristics of liner systems in various waste containment and other facilities. Annular specimens with a 300-mm inner diameter and a 500-mm outer diameter are tested by the apparatus. This apparatus consists of four components: (1) the vertical loading system, (2) the torsional shearing system, (3) the multifunctional shearing box, and (4) the process control and data acquisition system. The advantages of this apparatus are as follows: (1) The specimen can be tested both in displacement control and stress control, during which the normal stress is maintained or varied as needed. (2) The maximum normal stress and shear stress that can be loaded are 2.39 and 2.59 MPa, respectively. (3) The shear displacement is unlimited and the real-time shear displacement of each interface in the liner system can be obtained. (4) Special nail plate panels are developed for clamping different types of geosynthetics. A new adaptive telescopic pressure plate device is also developed for testing other materials, such as the clay layer and sand layer, and adapting to its compression deformation without lateral deformation. The performance of the apparatus is comprehensively evaluated by the conventional shear mode experiment and mode switching shear experiment of the textured geomembrane/geotextile interface and the conventional shear experiment of the composite liner system.