Contacts and beams (water flow)

The frame "Contacts" ("Beams") contains a table with the list of contacts (beams). Adding (editing) contacts is performed in the "New contacts" dialog window.

The contact elements are used in applications that require a proper representation of structure-soil interaction. They can be further used to model joints or interfaces of two distinct materials (soil – rock interface). Contacts are assigned to already defined lines – free lines or mesh lines (interfaces). The contact is defined by its type.

Contacts can also be introduced using the mouse. This inputting mode is activated by clicking an appropriate button on the horizontal tool bar "Contacts". The following modes are available:

Add	The contact is introduced by clicking the left mouse button at a desired location on the desktop
Adjust	Clicking the left mouse button on already existing contact opens the "Adjust contacts properties" dialog window, which allows for modifying its parameters.
Remove	Clicking the left mouse button on already existing contact opens the contact removal dialog window – accepting this action removes the selected contact.

The inputted contacts can also be edited on the desktop with the help of active objects.

Beam or contact element can be defined as:

-	permeable
-	impermeable
-	partially permeable

Contact elements allow us to model a certain barrier for flow in the soil body. Consider for example a sheeting wall represented in the stress analysis by beam elements. The sheeting wall anchored into the inside region can be considered either as fully permeable, or fully impermeable or partially permeable. Although the first two cases can also be treated using contact elements placed along the corresponding line, they are handled by the program automatically without needing these elements. The third case represents a problem of flow in a thin zone having a given thickness d, see figure:

Partially permeable contact

Corresponding fluxes in the tangent direction (s-direction) q_s and normal direction (n-direction) q_n are given by:

Defining contact elements therefore requires inputting the following parameters:

ks	-	permeability in tangent direction (permeability longitudinal), [m/day]
kn	-	permeability in normal direction (permeability transverse), [m/day]