Impact of elevated temperature from water cooling system on contaminant transport in clay liners: A laboratory and numerical investigation

In municipal solid waste landfills (MSWL), the center and peripheral regions of the basal compacted clay liner (CCL) often experience steady elevated temperatures due to waste biodegradation and cyclic temperatures similar to the seasonal atmospheric temperature patterns, respectively. In the present study, the negative effects of cyclic elevated temperatures on the desiccation behaviour of a MSWL basal CCL was examined by subjecting CCL samples to multiple wet-dry cycles with different drying temperatures. It was observed that the extent of desiccation cracking experienced by the CCL rose as the drying temperature and number of wet-dry cycles increased. The present study also assessed the effect of different thermoplastic cooling pipes on the reduction of temperature rise and desiccation experienced by CCLs exposed to constant elevated temperatures (CETs). It was observed that the introduction of thermoplastic cooling pipes led to a significant attenuation of the final temperature (FT) and desiccation magnitude along the CCL depth in the face of all applied CETs, irrespective of the cooling pipe material employed. A comprehensively analysis of the final temperature distributions within the entire CCL, coolant and sand layer surrounding the cooling pipe was also carried out via the conduction of a numerical simulation. Overall, the present study revealed the adverse effects imposed by cyclic elevated temperatures on a CCL and the potential that thermoplastic cooling pipes possess to successfully reduce the temperature rise and desiccation experienced by a CCL in the face of different CETs.