MDC > Theoretical Notes > Computation Process & Conventions

Verification of the wall is done in the following sequence:

Phase I

Terrain pressures and any surcharge on the stem are calculated. The stem is then divided into a fixed number of segments that will hereafter be the verification segments. For this phase, the thrust surface is taken to be the face of the stem. If Coulomb 's method is selected the thrust is considered at an angle corresponding to the terrain wall angle of friction declared in the geotechnic properties. If Rankine's method was selected the thrust is considered to be horizontal. In phase I, the program determines stresses only on the stem and performs structural verification using the materials specified by the user and the selected criterion (Admissible Tension, or Limit State).

Phase II

In this phase pressures calculations are repeated taking as thrust surface the vertical line that passes through the uphill edge of the foundation heel. This time, with Coulomb’s method, it is the angle of soil resistance that is used. Then all pressures (Overturning and stabilizing moments) are determined in respect to the datum point that is the lower corner of the foundation toe. Thereafter the program performs Ultimate limit state, Overturning, Sliding, and Limit load verifications.

Phase III

In this phase the stresses on the footing shelves, segmented to a fixed number, are determined. Then structural verification on the footing is performed.
If the footing is not anchored on piles, this completes the calculation.

Phase IV

This phase is only relevant where pile further support the footing. Stresses transmitted by the wall to the piles are consist in the moments obtained in phase II. The user may chose to have transmitted to the piles the net resulting moment (difference between overturning and stabilizing) or only the overturning one. Clearly this latter choice is only reasonable where the overturning moment far exceeds the stabilizing. If more than one line of piles is declared, the program performs verification calculation on the line that is most stressed (normally by compression).