DSD-INT 2017 Integrating various data types when building a 3D model of the subsurface on a local...

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)

3D model of the geology below a highway

marc.hijma@deltares.nl