A Novel Method for Modeling Complex 3D Geological Body with Strata Pinch-out

Transcription

1 July 29 th IGARSS 2011 Vancouver, Canada A Novel Method for Modeling Complex 3D Geological Body with Strata Pinch-out Jiateng Guo 1, Yizhou Yang 1, Lixin Wu 1,2, Rongbing Zhang 1 1, 2 Academy of Disaster Reduction and Emergency Management Beijing Normal University, Beijing, China

2 Outline 1 Introduction 2 Methodology 3 Application sample 4 Conclusions

3 Introduction 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.

4 Geotechnical Boreholes Define a Series of Section Lines

5 2D Section Map

6 3D Geological Model How can we get this model from boreholes automatically?

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

8 Sequential Strata

9 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?

10 Degradation of GTP (a) Pyramid (b) GTP (c) Tetrahedron

11 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.

12 Step 2. Standard GTP Modeling a,a b b a a c c a,a GTP a,a a a a a c a b a b b Side-edge c c b b TIN-face c,c b,b c,c GTP-body Side-edge TIN-face a,a b,b c,c GTP-body

13 Step 3. Simple Degradation of GTP Redundant triangles are deleted. GTP Side-edge TIN-face P 1 P 2 P 3 / / P 1 P 2 P 3 GTP-body P 1 P 3 P 6 P 4 P 3 P 6 P 4 P 1 P 3 P 4 P 1 P 3 P 4 P 3 P 6 P 4 P 1 P 2 P 5 P 4 / P 1 P 2 P 5 P 2 P 5 P 4 P 1 P 2 P 5 P 2 P 5 P 4 P 2 P 3 P 6 P 5 P 3 P 6 P 5 P 2 P 5 P 6 P 2 P 5 P 6 P 3 P 6 P 5 P 4 P 5 P 6 / / P 4 P 5 P 6

14 Step 3. Simple Pinch-out The pinch-out points are all at the boreholes, however ½ pinch-out 1/3 pinch-out

15 Step 4. Parameterized Degradation of GTP b b b b b,b c m c a o n c,c a a,a b Side-face TIN-face c b,b o c Ⅰ m Ⅰ b a c c a m n c,c o Ⅱ a n Ⅱ a,a Reconstruction of degradated GTP component according to pin-out scale

16 Step 4. Parameterized Degradation of GTP TIN-face Pinch-out Side-face Pinchout

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

18 Step 4. Parameterized Degradation of GTP GTP (Father component) GTP (Child component) Side-edge a-bb c c o-bb c c o-abc o-acc o-abb TIN-face bc-aa a-mnc a-mbc a-a mn Topological relations between GTP(father) with GTP(child)

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

20 Application Sample Fence slices Planar slice Crossing sections Curvilinear sections

21 Integral Roaming

22 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.

23 Thanks for your attention!