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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 the assessment schema described in VTV-2006.
!Figuur globale toetsschema nieuw.jpg|width=800!
Figure 1: Assessment 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) is determined by the relation:
M = 2 H{~}vw~ + 1.5 (H - H{~}vw~)
where H is the channel depth and H{~}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 ≥ 40 m)
*2. Determination of the assessment level*
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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 damaging criterium is not met if the liquefaction point S{~}ZV~ is situated landwards of the observation point S{~}sign~.
where S{~}sign~ is the intersection point between the observation profile (from the foreshore) and the assessment level and
S{~}ZV~ is the intersection point between the existing profile and the assessment level.
h5. Step 2: Artificially underwater installed and non-compacted sandy foreshore?
By lack of information, *D-FLOW SLIDE* assumes that no artificially underwater installed and non-compacted sandy foreshore is present (step 2 of the Global check).
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: Is liquefaction 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? |
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