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GGU-UNDERPIN: Double-bounded surcharges (active side)

If two bounded surcharges are defined as follows:

image-20241202-104237.png

  • Bounded surcharge 1:
    begins at x = 1,00 m and has the value p.
  • Bounded surcharge 2:
    begins at x = 2,00 m and has the same value as surcharge 1 but with a negative sign
    (see the explanation on the previous page).

A double-bounded surcharge, which acts as a consequence of p at x = 1.00 to x = 2.00, is thus defined as the result of earth pressure analysis. However, the graphics are not really satisfactory and may be irritating for an examiner. Double-bounded surcharges were therefore introduced.

image-20241202-104321.png

The same result is achieved as for the definition provided by Figure 11 but with improved graphics, provided the control parameter is set to 1.0 (see “"Double-bounded surcharges" menu item”). For smaller values the linear component of the negative surcharge is only partly adopted, and the earth pressure from the double-bounded surcharge is then greater.

The area loads described in Section “Area loads” are based on different assumptions for the resulting earth pressure (including a different approach for the earth pressure coefficient in stratified ground), so the definition of a double-bounded surcharge does not provide the same result as an equivalent area load.