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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
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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
Step 4. Parameterized Degradation of GTP
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c,c’
m
n
a
b,b’
b
a,a’
b’
c o
c’
Division of parameterized degradation GTP component
Step 4. Parameterized Degradation of GTP
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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)
Step 4. Parameterized Degradation of GTP
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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.
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