This paper reports the findings of a unique field instrumentation project on a steep, 1(v) in 2.3(h), landfill cap. Displacements and strains were monitored during and post placement of restoration soils above a geosynthetic cap. The relative geosynthetic interface displacements were measured between the Geomembrane (GM) and both an underlying geotextile and an overlying Geocomposite Drainage Layer (GDL). The instrumentation was installed during 2014 and was monitored over a five-month pe-riod. The instrumentation comprised two monitoring tables each with six extensometers to measure dis-placement and relative displacement within the geosynthetic lining system of the landfill cap. The loca-tions of the extensometers were 10, 15 and 20m below the crest of the slope for both the GM and GDL. All of the extensometers cables were installed over the GM and underneath GDL panels. Additionally, six DEMEC strain gauge installations were made, each comprising a set of 4 markers to facilitated four strain measurements at each of the six locations (two measurements across the slope and two measurements along the slope). Displacements were reported in the GM and at the GM – GDL interface that were indica-tive of post peak conditions, however, it should be noted that the displacements occurred at low confining stresses where displacements induced interface wear is less prevalent.
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