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This section uses the results of a by-hand calculation performed for three profiles of the Spui dike project (see figure below):

  • km 63.9 (Nieuw Beijerland)
  • km 65.0 (between Oud Beijerland and Nieuw Beijerland)
  • km 67.8 (Oud Beijerland)

As the details of the calculation performed by hand are not available, those benchmarks are set in group 2.

2.1. Spui dike at km 63.9 (Nieuw Beijerland)

Description

The dike profile at hmp 63.9 is given in the figure below.

The soil profile and the material properties are given in the following table:

Top level
(m NAP)

Material

Formation

Sensitive
to
liquef.

Dr
(%)

n
(%)

nmin
(%)

nmax
(%)

γunsat
(kN/m3)

γsat
(kN/m3)

γgrains
(kN/m3)

D50
(mm)

D15
(mm)

φ
(deg)

c
(kPa)

Grond level

Clay

Dunkirk / anthropogenic

No

 

 

 

 

18

18

26.5

 

 

25

0

-0.5

Clay/Sand

Dunkirk

No

 

 

 

 

18

18

26.5

 

 

25

0

-6.5

Peat

Holland

No

 

 

 

 

10

10

26.5

 

 

25

0

-7.5

Clay

Calais

No

 

 

 

 

18

18

26.5

 

 

25

0

-8.5

Sand clayey/Sand

Calais

Yes

34.6

45

36.5

49.5

19

19

26.5

0.160

0.080

25

0

-9.5

Sand

Calais

Yes

30.0

45.6

36.5

49.5

20

20

26.5

0.160

0.080

30

0

-12.5

Sand

Calais

Yes

24.6

46.3

36.5

49.5

20

20

26.5

0.160

0.080

30

0

-18

Sand

Pleistocene

Yes

60.0

41.7

36.5

49.5

20

20

26.5

0.160

0.080

35

0

The other calculation parameters used are:

  • Water level: 0.9 m
  • Required probability of failure of the dike: 1:4000
  • Percentage probability of failure byliquefaction: 1 %
  • Model factor: 1
  • Area ratio (c = A2/A1): 1.4
  • Standard deviation cot(gamma): 4.6
  • Considered dike length: 100 m
Benchmark results

According to the by hand calculation, both Global and Advanced checks fail.

D-FLOW SLIDE results

By lack of information, the following values are chosen:

  • A state parameter (for Global step 5 and Detailed checks) of -0.05
  • A critical retrogression length of 34.353 m (which corresponds to the foreland length = 79.035 m - 44.682 m)
  • A migration velocity foreshore of 100 mm/year
  • For the state parameter per layer, a value of -0.04 is used for sand layers and -0.06 for the other layers.

 

D-FLOW SLIDE results are in accordance with the results by hand as show in the table below.

Method

Benchmark

D-FLOW SLIDE

Relative error

Global check

Failed

Failed

OK

Detailed check

Failed

Failed

OK

2.2. Spui dike at km 65.0 (between Oud Beijerland and Nieuw Beijerland)

Description

The dike profile at km 65.0 is given in the figure below.

The soil profile and the material properties are the same as for the profile at km 63.9 (see paragraph 2.1).

Benchmark results

According to the by hand calculation, both Global and Advanced checks pass.

D-FLOW SLIDE results

By lack of information, the following values are chosen:

  • A state parameter (for Global step 5 and Detailed checks) of -0.05
  • A critical retrogression length of 10.930 m (which corresponds to the foreland length = 36.817 m - 25.887 m)
  • A migration velocity foreshore of 100 mm/year
  • For the state parameter per layer, a value of -0.04 is used for sand layers and -0.06 for the other layers.

 

D-FLOW SLIDE results are not in accordance with the results by hand as show in the table below.

However, by lack of information about the hand calculation, it can't be concluded that the program gives incorrect results.

Method

Benchmark

D-FLOW SLIDE

Relative error

Global check

Passed

Failed

not OK

Detailed check

Passed

Failed

not OK

2.3. Spui dike at km 67.8 (oud Beijerland)

Description

The dike profile at km 67.8 is given in the figure below.

The soil profile and the material properties are given in the following table:

Top level
(m NAP)

Material

Formation

Sensitive
to
liquef.

Dr
(%)

n
(%)

nmin
(%)

nmax
(%)

γunsat
(kN/m3)

γsat
(kN/m3)

γgrains
(kN/m3)

D50
(mm)

D15
(mm)

φ
(deg)

c
(kPa)

Grond level

Clay

Dunkirk / anthropogenic

No

 

 

 

 

18

18

26.5

 

 

25

0

-0.5

Clay/Sand

Dunkirk

No

 

 

 

 

18

18

26.5

 

 

25

0

-4

Peat

Holland

No

 

 

 

 

10

10

26.5

 

 

25

0

-5

Clay

Calais

No

 

 

 

 

18

18

26.5

 

 

25

0

-6

Sand

Calais

Yes

20

46.9

36.5

49.5

20

20

26.5

0.160

0.080

30

0

-20

Sand

Pleistocene

Yes

60

41.7

36.5

49.5

20

20

26.5

0.160

0.080

35

0

Benchmark results

According to the by hand calculation, the Global check fails and the Advanced check passes.

D-FLOW SLIDE results

By lack of information, the following values are chosen:

  • A state parameter (for Global step 5 and Detailed checks) of -0.05
  • A critical retrogression length of 42.098 m (which corresponds to the foreland length = 97.460 m - 55.362 m)
  • a migration velocity foreshore of 100 mm/year
  • For the state parameter per layer, a value of -0.04 is used for sand layers and -0.06 for the other layers.

 

D-FLOW SLIDE results are in accordance with the results by hand, as show in the table below. According to D-FLOW SLIDE, the

 

Method

Benchmark

D-FLOW SLIDE

Relative error

Global check

Failed

Failed

OK

Detailed check:

Result

P(Z) < P(Z)allowable

 

-

Yes

 

Failed

Yes

 

-

OK

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