Cyclic shear testing of a multi-component geosynthetic clay liner

The design of a petrochemical processing and storage facility involved evaluation of several secondary containment liner options. One of the options considered was a needlepunch-reinforced woven/nonwoven geosynthetic clay liner (GCL) with a polyethylene geofilm laminated to the non-woven side. Since the project site was located in a seismically-active area, design engineers were concerned about the ability of the multi-component GCL to withstand seismic loads. To assess the potential for damage to the GCL when subjected to seismic loads, a cyclic shear test of the proposed liner cross-section (sand/multi-component GCL/sand) was performed using a large dynamic direct shear machine, capable of applying static and dynamic loads to soil and geosynthetic specimens. Cyclic shear testing under a normal stress of 100 kPa found that shearing occurred at the sand/geofilm interface, with the GCL sustaining no visible damage even after 25 cycles of loading with a displacement amplitude of 20 mm and a frequency of 1 Hz. Material property tests performed on pre-cyclic and post-cyclic GCL samples provided additional evidence that the GCL specimen did not sustain damage due to cyclic loading. The cyclic shear testing procedure described in this paper could be useful for not only evaluating the performance of liner systems during seismic events, but also for evaluating the potential for liner system damage due to dynamic equipment loading during installation and soil covering operations.