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1. Global check (VTV-2006)

1.1 Check on liquefaction

The global check for liquefaction as implemented in D-Flow Slide is shown in the schema below. It is based on steps 1 t/m 5 described in VTV-2006, except that step 2 of VTV is skipped.

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Figure 1: Checking schema for liquefaction

Step 1 - Geometrical check: damaging criterium liquefaction

The damaging criterion 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). The margin is now determined by the relation:

M = 2 Hvw + 1.5 (H - Hvw)

where H is the channel depth and HVW is the thickness of the sensitive layer. If over the entire channel depth softening sensitive sand is present, this margin is thus equal twice the fictive channel depth (M = 2 H).
The inclined part of the observation profile in line with the horizontal portion. The inclinaison of the slope depends on the channel depth:

  • 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

3. Comparison of the observation profile with the existing profile
X Ssign = X co-ordinaat of the observation profile from the foreshore
X SZV = X co-ordinaat of the liquefaction point from the foreshore

Step 2: Artificially underwater installed and non-compacted sandy foreshore?
Step 3: Is the dumping criterion satisfy?

Directly in front of the toe of the dike or on the outside of the toedumping or to the outward end of a dumping, the slope 1:2.5 may not be cut by the profile.

Step 4: Liquefaction is possible on the basis of geometry?

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: Are there any sensitive to liquefaction layers present?
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