Elevated temperature effects on interface shear behavior

Environmental conditions such as temperature inevitably impact the long term performance, strength and deformation characteristics of most materials in infrastructure applications. The mechanical and durability properties of geosynthetic materials are strongly temperature dependent. The interfaces between geotextiles and geomembranes as well as between granular materials such as sands and geomembranes in landfill applications are subject to temperature changes due to seasonal temperature variations as well as exothermic reactions occurring in the waste body. This can be a critical factor governing the stability of modern waste containment lining systems. Historically, most laboratory geosynthetic interface testing has been performed at room temperature. Information today is emerging that shows how temperatures in liner systems of landfills can be much higher.;An extensive research study was undertaken in an effort to investigate temperature effects on interface shear behavior between (a) NPNW polypropylene geotextiles and both smooth PVC as well as smooth and textured (co-extruded, structured) HDPE geomembranes and (b) sands (rounded, angular) and smooth PVC and HDPE geomembranes. A unique temperature controlled chamber (TCC) was designed and developed to be utilized to simulate the field conditions at elevated temperatures and evaluate shear displacement failure mechanisms at these higher temperatures. The physical laboratory testing program consisted of multiple series of interface shear tests between material combinations found in landfill applications under a range of normal stress levels from 10 to 400 kPa and at a range of test temperatures from 20 to 50 °C.;Complementary geotextile single filament tensile tests were performed at different temperatures using a dynamic thermo-mechanical analyzer (DMA) to evaluate tensile strength properties of geotextile single filaments at elevated temperatures. The single filament studies are important since the interface strength between geotextiles and geomembranes is controlled by the fabric global matrix properties as well as micro-scale characteristics of the geotextile such as filament strength and how it interacts with the geomembrane macro-topography.;It is known that the peak interface strength for sand-geomembrane as well as geotextile-geomembrane interfaces is mainly attributed to the geomembrane properties such as hardness and micro surface roughness. To this end, the surface hardness of smooth HDPE and PVC geomembrane samples was measured at different temperatures in the temperature controlled chamber to evaluate how temperature changes affect the interface shear behavior and strength of geomembranes in combination with granular materials and/or geotextiles. The aim of this portion of the experimental work was to examine: (i) the change in geomembrane hardness with temperature; (ii) develop empirical relationships to evaluate shear strength properties of sand-geomembrane interfaces as a function of temperature; and (iii) compare the results of empirically predicted frictional shear strength properties with direct measurements from the interface shear tests performed at different temperatures.