The degradation of solid waste in landfills results in the coupled migration of gas and leachate through the pore spaces in waste material. The existing analytical methods cannot be used to obtain a solution for the gas-leachate coupled migration problem. This study used the differential quadrature method to solve the gas and leachate phase continuity equations considering the effect of the gas-leachate coupling. The calculation results were verified based on the calculated data of previous studies. The results of the field gas collection tests and the laboratory degradation tests were fitted using the peak gas generation equation. The peak values of gas generation were found between 0.94 and 20.29 years in the field tests, and between 0.09 and 0.19 years in the laboratory tests. The gas pressure calculated by parameters fitting of the field tests and the laboratory tests were less than 1 kPa and greater than 8 kPa, respectively. Considering the gas-leachate coupling effect, the pore gas pressure in the simulated landfill increased by approximately 20%, and the peak pore gas pressure occurred slightly earlier than that without consideration of the coupling effect.
Keywords: Landfill gas; coupled migration; degradation parameters; differential quadrature method; field tests; leachate.