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h1. 1. Global check (VTV-2006)

h3. 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.

!Figuur globale toetsschema nieuw.jpg|width=1000800!
Figure 1: Checking schema for liquefaction

h5. 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 HvwH{~}vw~ + 1.5 (H - HvwH{~}vw~)

where H is the channel depth and HVWH{~}vw~ 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 ≥&nbsp;40 m)

*2. Determination of the assessment level*

*3. Comparison of the observation profile with the existing profile at the assessment level*
The criterium is met if: X Ssign{~}Ssign > X{~}SZV~ 
where:
X{~}Ssign~ = X co-ordinaatcoordinate of point S{~}sign~, the intersection between the observation profile (from the foreshore) and the assessment level;
X{~}SZV~ SZV = X co-ordinaatcoordinate of liquefaction point S{~}ZV~, the liquefaction point from the foreshoreintersection between the existing profile and the assessment level.

h5. Step 2: Artificially underwater installed and non-compacted sandy foreshore?

h5. 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.

h5. 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.

h5. Step 5: Are there any sensitive to liquefaction layers present?