Contents - Index

Boundary Conditions

Boundary conditions must be set up, before a seepage analysis can be conducted.  There are two types of boundary conditions, equipotential boundary and no-flow boundary.
An equipotential boundary is a surface on which the total head is fixed.  Some part of the top surface is submerged under water, where the equipotential equals the water head, and some part of the top surface is exposed, where the equipotential equals zero.  To set up an equipotential boundary, water lines can be used.
A no-flow boundary is a surface across which there is no water flowing out or in (for example, an impermeable soil layer or an impermeable wall).  The side boundaries usually should also be considered as a no-flow boundary, since they are far away where the hydraulic gradient equals zero across the boundary.  To establish a no-flow boundary, limit lines or pile lines can be used.