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Integrating various data types for building
2/3D models of the subsurface for risk assessments
Marc Hijma
Applied Geology and Geophysics
27 oktober 2016
• Easy to use tool to visualize large sets of subsurface data
• Easy to use tool to create 2D/3D models of the subsurface for risk-
assessments
• Two examples • Assessing a measure against backward-erosion piping
• Stochastic subsurface scenario’s below Dutch dikes
iMOD – 2/3D MODELS – RISK ASSESSMENTS
iMOD – Creating 3D-model of very complex subsurface
Backward-erosion piping
Several possible measures
Berm
Drains
Several possible measures
Berm
Drains
Geotextile
Van der Herik, Sliedrecht
Several possible measures
Berm
Drains
Geotextile
Coarse-sand barrier
Coarse-sand barrier
Coarse-sand barrier
Coarse-sand barrier
Coarse-sand barrier
Coarse-sand barrier
The goal: create the best possible 3D-model
This work is done together with MSc.-student Amir Argaman
Merge all borehole-logs into one iMOD file with similar lithological classes
Using kriging: create first rough 3D-model of lithological variation
Using geological knowledge: identify main units and improve the interpolation
Put hard data in: location and infill of lakes, filled-in lakes, berms, dikes
Using local measurements: head, permeability
Create 3D-groundwater model that is needed to analyze the coarse-sand barrier
To be continued….
iMOD – Creating stochastic scenario’s
Stochastic subsurface scenario’s below Dutch dikes: 3500 km
Stochastic subsurface scenario’s: subsurface is very important
3D model of the geology below a highway
Point data not enough to capture variability
Stochastic approach using iMOD
6 december 2017
0
-5
-10
Gebied II
50% 50%
0
-5
-10
Gebied III
30% 30% 30% 10%
0
-5
-10
Gebied I
15% 40%5% 20% 20%
0
-5
-10
Gebied IV
15% 10% 25% 45% 5%
I
II
III
IV
Stochastic approach using iMOD
6 december 2017
iMOD: 2D sections along a dike.
Creating subsurface scenarios
8 juni 2015
• Each scenario gets its own probabity of occurence
• Depth of each layer: modal, maximum, minimum
6 december 2017
Combined probability of failure
Used for all primary levees!
3500 km dikes
1081 segments (gem. 3.3 km)
5573 scenario’s (5 per segment on average)
