1. Global
...
check
The global check as implemented in D-Flow Slide is based on the assessment schema described in VTV-2014 and may comprise the following steps
...
Step 1 : Would flow slide lead to damage on levee (i.e. is the "schadelijksheidscriterium" met)?
The criteria of harmfulness ("schadelijksheidscriterium" in Dutch) checks if the “signaleringsprofiel” does not have overlap with the so-called zone of influence of the levee (“invloedszone”). is met if at the so-called assessment level is situated within the slope (i.e. on landward side of) the so-called observation profile, in accordance with Annex 9.4 of the VTV-2006.
1) Determination of the observation profile
The required margin (the horizontal part from the outside toe of the dike) depends on the presence of a revetment and is determined by the relation:
...
- 1:15 if the fictive channel depth is less than 40 m (H < 40 m)
- 1:20 if the fictive channel depth is more than 40 m (H ≥ 40 m)
2) Determination of the assessment level
The assessment level is the lower boundary of the liquefiable sand layer, but has a minimum and maximum of H/3 and H/2 above the bottom of the channel respectively.
3) Comparison of the observation profile with the existing profile at the assessment level
The criteria of harmfulness is not met if the liquefaction point SZV is situated landwards of the observation point Ssign.
where:Ssign is the intersection point between the observation profile (from the foreshore) and the assessment level and
SZV is the intersection point between the existing profile and the assessment level.
...
If the liquefaction point SZV is situated landwards of the observation point Ssign, the criteria is not met, which means that the global check PASSES.
If the liquefaction point SZV is not situated landwards of the observation point Ssign, the criteria is met, which means that the check in step 3 must be performed.
Step 2: Criterion on slope protection met (<1:2,5)?
Directly in front of the toe of the dike or on the outside of the toe dumping or to the outward end of a dumping, the slope 1:2.5 may not be cut by the profile.
This check should be performed only if the answer to question 1 is "No". However, as the result has no influence on the result assessment, this check is not performed.
...
Step 3: Artificially underwater installed and non-compacted sandy foreland?
The answer to this question is given as input by the user, in the "General (Additional) Parameter".
...
Step 4: Flow slide possible based on geometry only?
The occurrence of a liquefaction is possible if one of the two following conditions is met:
- The average slope is steeper than or equal to 1:4, over a height of at least 5 m;
- The total slope (channel edge-channel bottom) is on average steeper than or equal to 1:7.
...
Step 5: Is liquefaction possible?
The answer is "Yes" if Ψ5m > -0.05 between the water line and 0.5H below the toe of the submerged slope.
...
Step 6: Are there any sensitive to liquefaction layers present (i.e. D50 < 200 μm or D15 < 100 μm averaged over a thickness of 5 m)?
The answer is "Yes" if D50 < 200 μm or D15 < 100 μm averaged over a thickness of 5 m between the water line and the toe of the channel slope.
...
Step 7: Is unstable breaching possible?
This criterion corresponds to step 5 of CUR Aanbeveling 113, 2008.
...