| 摘要 |
A low-permeability zone analogous to natural low permeability zones is deliberately formed within a landfill, mine tailings or other cover system to prevent the migration of water or other substances into or out of the wastes being isolated. Natural low-permeability zones such as caliche, calcrete, silicrete or gypcrete are formed by natural processes including leaching, transport, and re-precipitation of slightly soluble minerals through the action of rain or other water percolating through the soil column. The deliberate formation and stabilization of a low-permeability zone is accomplished by the (1) intentional addition of appropriate minerals or other materials to affect the supply of chemical components or to change the soil physical properties such as permeability or porosity, (2) judicious application of water or other solutions to increase the rate of transport, dissolution or precipitation, (3) compaction of these minerals, and (4) design of the overlying layers to provide the optimum stabilization of the seal. Appropriate minerals for the man-made low-permeability zone or chemical seal include those minerals that form natural low-permeability zones in soils.
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