igarss2011_guojiateng.pdf

Institute for Geo-informatics

& Digital Mine Research www.dgmine.com

July 29th IGARSS 2011 Vancouver, Canada

A Novel Method for Modeling Complex 3D

Geological Body with Strata Pinch-out

1 Institute for Geo-informatics & Digital Mine Research

Northeastern University, Shenyang, China

2 Academy of Disaster Reduction and Emergency Management

Beijing Normal University, Beijing, China

Jiateng Guo1, Yizhou Yang1, Lixin Wu1,2, Rongbing Zhang1


& Digital Mine Research www.dgmine.com Northeastern University

Shenyang, China

Outline

Introduction 1

Methodology 2

Application sample 3

Conclusions 4



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In geotechnical engineering and mining domain,

geologists and miners usually use 2D section

map to describe the underground strata, however,

it’s very difficult to imagine and understand the

spatial situations of geological structures.

The motivation of our work is to present a 3D

data model for constructing 3D geological body

from borehole data. The data model should be

available in handling complex geological

structures, such as strata pinch-out.

Introduction



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Geotechnical Boreholes

Define a Series of

Section Lines



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2D Section Map



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3D Geological Model

How can we get this model from boreholes automatically?



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GTP Data Model

Generalized Tri-Prism (GTP) Model (Wu Lixin, 2004)

1. Construct D-TIN (Delaunay Triangular Irregular Net) from the collar

points of boreholes;

2. Extend each triangle of the D-TIN along oblique borehole track to

generate general tri-prisms, and finally the geological body can be

constructed by combination of GTP components.



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Sequential Strata



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Strata Pinch-out

Strata Pinch-out: The thickness of the strata layer becomes thinner

and thinner on a particular direction. The out line of the layer even reduced

to be a point.

How can we construct the 3D model for strata pinch-out ?



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Degradation of GTP

(a) Pyramid (b) GTP (c) Tetrahedron



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Step 1. Borehole Data Pre-processing

The borehole strata

is not integral for

lack of layer 4 and

layer 7.

Virtual points are added

to keep strata integrity of

the borehole, and the

thickness value of

inserted layer is assigned

0.

1

2

3

4

5

6

7

8



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b

b’

Side-edge

degradation TIN-face

degradation GTP-body

degradation

a

a,a’

c

c’

a,a’

b

b’

c,c’

a,a’

c,c’ b,b’

c

c’

b

b’

a’ GTP

c

a

Side-edge degradation TIN-face degradation

GTP-body degradation

a

a

a

a

b

a

a,a’

c,c’

b,b’

Step 2. Standard GTP Modeling



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GTP Side-edge

degradation TIN-face

degradation GTP-body

degradation P1P2P3 / / △P1P2P3

P1P3P6P4 △P3P6P4 △P1P3P4 △P1P3P4 △P3P6P4

P1P2P5P4 / △P1P2P5 △P2P5P4 △P1P2P5 △P2P5P4

P2P3P6P5 △P3P6P5 △P2P5P6 △P2P5P6 △P3P6P5

P4P5P6 / / △P4P5P6

Step 3. Simple Degradation of GTP

Redundant triangles are deleted.



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Step 3. Simple Pinch-out

The pinch-out points are all at the boreholes, however …

½ pinch-out 1/3 pinch-out



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a

a’

b,b’

c,c’

m

n

c’

a,a’

b

b’

c o

c,c’

a,a’

b

b’

c’

c o

b’

c o

b

c’

a’

n

a

m m

n

a

b,b’

TIN-face degradation

Ⅰ Ⅱ

Ⅰ Ⅱ

Side-face degradation

Reconstruction of degradated GTP component according to pin-out scale

Step 4. Parameterized Degradation of GTP



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TIN-face

degradation

Pinch-out

Side-face

degradation

Pinch-

out




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c,c’

m

n

a

b,b’

b

a,a’

b’

c o

c’

Division of parameterized degradation GTP component




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degradation GTP

（Father component） GTP

(Child component）

Side-edge

degradation a-bb’c’c

o-bb’c’c o-abc o-acc’

o-abb’

TIN-face degradation bc-aa’ a-mnc a-mbc a-a’mn

Topological relations between GTP(father) with GTP(child)




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Application Sample

68 boreholes, the 4th, 5th and 7th layer are pinch-out strata .



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Fence slices Planar slice

Crossing sections Curvilinear sections

Application Sample



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Integral Roaming



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Conclusion

Parameterized Degradation GTP (PD-GTP), which was improved from simple degradated GTP model, is more accurate for constructing pin-out strata.

The pinch-out scale can be assigned proper values according to geologists’ experience.

We have developed a software (GeoIntAnalyzer V1.0) for 3D modeling and analysis of spatial objects in geotechnical engineering area.



Shenyang, China

Thanks for your attention! [email protected]

igarss2011_guojiateng.pdf

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