Study of leachate recharge model and vertical well design method for bioreactor landfills

Leachate recharging not only solves the leachate treatment problem but also has tremendous environmental and engineering benefits. In this study, a recharge model was developed based on consideration of the inhomogeneous characteristics of the pile and the degree of clogging of the leachate collection and removal system (LCRs), and a design diagram of the maximum injection pressure P_s and the minimum setback distance d_s was given. The following conclusions are obtained: the rate of diffusion in the horizontal and burial depth directions depends on anisotropy coefficient A, and the rate of development of the blocked water level on the LCRs depends on the degree of blockage h₁. The development rate of the region affected by the recharging is low at the beginning of the recharging and increases rapidly when the moment T_b is reached, which decreases with the injection pressure P, and the degree of blockage h₁. The safety factor of slope F_s decreases at a slower rate when the anisotropy coefficient is 0 < A < 1 and 15 < A < 20, and at a faster rate when 1 < A < 15. When the LCRs is blocked, the injection pressure P and anisotropy coefficient A increase the degree of influence on the recharge efficiency and slope stability, and when the blocked water level h₁ > 30 m, recharge is not recommended. This model and the vertical well design method can well simulate the recharging process and its effect on the slope stability and provide a reference for the design of vertical wells.