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Linfluence is the length of the influence zone from the outer dike toe
De "invloedslijn" is defined as "de uiterste lijn op het maaiveld waarvoor geldt dat als aan dijkzijde van die lijn het maaiveld wordt verstoord de veiligheid van de waterkering zakt onder de (volgens de toetsing) vereiste veiligheid, gelet op alle directe faalmechanismen"
The influence zone is defined as follows: if this zone is damaged by an indirect failure mode, for example a flow slide, the safety of the dike drops below the required safety level, considering all direct failure modes. At surface level the influence zone is confined by the influence lines (in Dutch: "invloedslijnen").
Schadelijksheidscriterium - Determination of the observation profile ("signaleringsprofiel") when a top revetement is present
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In case no slope protection is present, if over the entire channel depth softening sensitive sand is present, this this margin is thus equal twice the fictive channel depth (M = 2 H), assuming that entire submerged consists of sand that is sensitive to liquefaction and/or breach flow.
The inclined part of the observation profile in line with the horizontal portion. The inclination of the slope depends on the channel depth:
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If the liquefaction point SZV is not situated landwards of the observation point Ssign, the criteria is not met, which means that the Global check PASSES.
Step 1b: Criterion on slope protection met (<1:2,5)?
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If this occurrence criterion not met, go to step 1e.
Step 1e: Is flow slide possible based on the occurrence criterion based on average geometry?
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Liquefaction flow criteria:
HR [m] is the fictitious height of the submerged slope in its most unfavourable situation during the assessment period and determined with:
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Other symbols in the figure below are (in Dutch):
LLWS LLWS meerjarig gemiddelde van het laagste springlaagwater ten opzichte van NAP, geldig in het kustgebied en de estuaria.
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- a slope with or without horizontal steps ("berms")
- the sand type:
- very fine sand with D50,5m ≤ 200 μm and D15,5m ≤ 100 μm
- medium fine sand with 200 < D50,5m ≤ 500 μm and 100 < D15,5m ≤ 250 μm
- coarse sand and gravel with Dwith D50,5m > 500 μm and D15,5m > 250 μm
where D15,5m and D50,5m are the minimum averaged values (only for sand and gravel soils) over a thickness of 5 m between the water line and the toe of the channel slope.
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- the calculated diameter D50;5m if a Detailed check is performed
- the calculated diameter D15;5m and D5D50;5m is if an Advanced Breach flow check is performed
In case of a incoherence, the Overall result gives a Warning message.
NOTE: In the current version of the program, it is not checked if the thickness is minimal 5 m. The average is performed over a thickness of 5 m, by not taking into account the none-sandy layers.
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