View
18
Download
0
Category
Preview:
Citation preview
Integrated Solver Optimized for the next generation 64-bit platform
Finite Element Solutions for Geotechnical Engineering
MIDASoft Inc.
Angel Francisco Martinez
Civil Engineer
Email : a.martinez@midasit.com
Slope Stability of Open
Pit Mine in 2D & 3D
Integrated Solver Optimized for the next generation 64-bit platform
Finite Element Solutions for Geotechnical Engineering
ContentsPart 1.
Part 2.
Part 3.
Part 4.
Part 5.
Objectives
Introduction
3D case
2D case
Conclusion
GTS NX
3
✓ Importing Terrain and Strata
✓ Meshing Higher Order Elements
✓ Importing materials from excel
✓ Water surface levels
✓ Generating 2D model out of 3D slice
✓ Excavation by stages
✓ Pseudo Seismic
✓ Results Interpretation SAM (LEM) vs SRM
✓ Results Interpretation in 2D vs 3D
Objectives
Integrated Solver Optimized for the next generation 64-bit platform
Finite Element Solutions for Geotechnical Engineering
ContentsPart 1.
Part 2.
Part 3.
Part 4.
Part 5.
Objectives
Introduction
3D case
2D case
Conclusion
GTS NX
7
In sequential excavation, the stability analysis of a shoring wall, slope and the effects
on the adjacent ground and structures are crucial.
Accurate ground material properties and geometry must be reflected. In addition, the analytical model needs
to closely reflect the excavation sequence.
Stage Analysis by FEM
The analysis is carried out by the FEM and is applied to large scale, deep excavations in the design and construction of
shoring wall and support systems. This method calculates displacements and stresses reflecting the elasto-plastic
behavior of ground and interaction with the shoring wall and support structures as well as the deformations in the
surrounding ground. Slope stability by strength reduction method is also necessary.
Introduction
Strength Reduction Method
In the strength reduction method, the shear strength c, (φ ) of the sloped ground material is gradually reduced until the point of divergence in calculation at which point slope failure is assumed to have taken place.
The maximum strength reduction ratio at that point is considered to be the minimum safety factor.
Such methods require iterative nonlinear analyses consuming significant analysis time, but they are manageable through the advancement in computing speed.
• For more accurate prediction of results in 3D analysis, use hexahedral element
dominated mesh
HexahedralTetrahedral Hybrid [Hexa dominated mesh]
Element shapes
Mesh (Elements)
Good for displacement Good for stress as well
Hexa elem.
Pyramid elem.
(connect hexa and tetra)
Tetra elem.
Terrain Import
• CAD-like features to generate/import terrain surface.
Import elevations of grids in sequence to create 3D terrain.
1
2 31
http://en.midasuser.com/training/tutorial_list.asp?nCat2=132
Topography and Boring Hole Import
[Puntos de mapa topografico se usan para crear superficie]
[Superficies geológicas 3D generadas
automáticamente a través de la
información de campo real
12
3
1
2
3
Tools to check or verify mesh quality
• Inspect and fix imported geometry
2
3
1
• Check Mesh Connections
Integrated Solver Optimized for the next generation 64-bit platform
Finite Element Solutions for Geotechnical Engineering
ContentsPart 1.
Part 2.
Part 3.
Part 4.
Part 5.
Objectives
Introduction
3D case
2D case
Conclusion
Materials and Properties
Mesh > Material
Import from excel
Create 3D solid properties
2
Procedure
1
3
2
1
3
GTS NX
32
Import terrain DXF to TGM
Extract geometry from DXF
Topography Map (DXF contour lines)
Extracted surface of topography
1
Download contour DXF map
(Google Earth, Web Database,
Etc)
Geometry > Tools > Terrain
Geometry Maker
Import DXF file into Terrain
Geometry Maker
Select lines and area for
topography surface
Save file to be exported
topography surface back to
GTS NX
2
2
Procedure
1
3
4
3
4
3
cadmapper.com
GTS NXImport bedding planes
1
Geometry > Surface & Solid >
Bedding Plane
Import > mine boring hole
Excel file
Leave X & Y distance as 0
Press Apply
2
Procedure
1
3
4
2
3
4
4
2
3
4
GTS NXDivide solid by surfaces
1
Geometry > Surface &
Solids > Box
Generate 3D Box with
dimensions shown to serve
as terrain solids.
Geometry > Divide > Solid
Select Extra geometries and
press DELETE
Check Duplicates
2
2
Procedure
1
3
4
GTS NX
3
2
Mesh layers
Top rock layer
Bottom weak layer Bottom rock layer
Top weak layer
1Mesh > Generate > 3D
Select top 2 geometries
Size 20
Hybrid Mesh
Material Top Rock Layer
Advanced >>
Check Higher Order Element
Uncheck Register sets
independent > Ok > Apply
Mesh 2nd layer as Top Weak
Layer
Mesh 3rd layer as Bottom Weak
Layer
Mesh 4th Layer as Bottom Rock
Layer
*note each layer has 2
geometries
Procedure
1
5
3
4
2
5
3
4
2
GTS NXLoads and BC
1
Static/Slope> Boundary>
Constraints
Self Weight > Z = -12
2
Procedure
1
2
1
Analysis Cases
1
Analysis > General >
Analysis Case > SRM
- Activate All
- Output Control > Check on
Strains
Name SRM
Run Analysis2
Procedure
1
2
2
GTS NX
32Iso-Volume Slices of critical slopes
3D Results
FOS 1.81FOS 1.56
With HOEWith LOE
Integrated Solver Optimized for the next generation 64-bit platform
Finite Element Solutions for Geotechnical Engineering
ContentsPart 1.
Part 2.
Part 3.
Part 4.
Part 5.
Objectives
Introduction
3D case
2D case
Conclusion
Export from GTS NX to SoilWorks
Limit Equilibrium Method (LEM)
A method for analyzing the stability of a slope in two dimensions. The sliding mass above the failure surface is divided into a number of slices. The forces acting on each slice are obtained by considering the mechanical equilibrium for the slices.
• Strength Reduction Method (SRM): The strength reduction method gradually decreases the shear strength and friction angle until the calculation does not converge, and that point is considered to be the failure point of the slope.
• Stress Analysis Method (SAM): This method first uses the finite element method to perform stress analysis on the slope and the safety factor for each various virtual slip surface, created from the assumptions of the limit equilibrium theory, is calculated based on the stress
analysis results
SRM SAM
2D Slope Stability
GTS NX
Export CAD from 3D to 2D
3D CAD Slice Export
1Geometry > Point & Curve >
Rectangle
Draw Rectangle Larger than
geometry side
Geometry > Transform >
Translate
- Move rectangle 330 meters in Y
Menu > Export > Soilworks
Neutral Format 3D
Target > 4 solids
Tool > 1 new surface
2
2
Procedure
1
3
3
GTS NXNew 2D file
New > 2D
Menu > Import < Neutral
Format
Geometry > Transform >
Rotate > -90 degrees about X
Translate > 2 point vector >
Select bottom corner to origin
(0,0,0)
2
Procedure
1
3
2
1
3
GTS NX
1
2
3
Import Materials
Mesh > Material
Import from excel
Create 2D Plane Strain
properties
2
Procedure
1
3
GTS NXMesh all 2d layers
1
Mesh > Generate > 2D
Mesh the layers in same
sequence as 3D model
Size: 10
Activate Higher Order
Element
2
2
Procedure
1
3
3
Boundary conditions for SAM
1
Static / Slope > Boundary
conditions
Auto Generate
Water Level
Gravity Load > Y = -1
Slip Surface Left
Slip Surface right
2
2
Procedure
1
3
4
3
4
5
5
SRM Analysis Cases
1
2
3
Analysis > General >
Analysis Case > SRM
- Activate All
- Output Control > Check on
Strains
Name SRM DRY
Analysis Case > SRM
- Activate All
- Output Control > Check on
Strains
- Analysis Control > Define
Water Level 1
Name SRM Saturated
2
Procedure
1
SAM Analysis Cases
1
2
3
Analysis > General >
Analysis Case > SAM
- Activate All except SAM
Right
Name SAM Left
Analysis Case > SAM
- Activate All ecept SAM
Left
- Analysis Control > Define
Water Level 1
Name SAM Right
Run All 4 analysis
2
Procedure
1
3
GTS NX
Dry Season FOS: 1.34
Left Slip Surface FOS 1.42
2D Results
Rainy Season FOS: 0.72
Right Slip Surface FOS 1.13
Construction Stage Analysis for Sequential Excavation Stability Inpsection
Bench Cuts in Stages
GTS NX
Draw 5 lines for cuts as shown following grid and remesh
Draw and Mesh 2D Bench Cuts
1
Geometry > Point & Curve >
Lines
Draw lines for Cute
Intersect All
Mesh 2D > Remesh
2
2
Procedure
1
3
3
2D Stages and Seismic Coeff.
1
Static Slope > Load > Gravity
Use Gx and Gy as seismic
Coefficients
Define Stages as shown, 4
excavations and last stage as
seismic coefficient load
Construction Stage Analysis
Case > Run
2
2
Procedure
1
3
3
GTS NX
Construction stage analysis can give FOS for each stage of excavation.
Exca 1: FOS 1.32
2D Sequential Excavation Results
Exca 2: FOS 1.30
Exca 4: FOS 1.18Exca 3: FOS 1.21
Stage 5 Seismic
FOS 1.01
Integrated Solver Optimized for the next generation 64-bit platform
Finite Element Solutions for Geotechnical Engineering
ContentsPart 1.
Part 2.
Part 3.
Part 4.
Part 5.
Objectives
Introduction
3D case
2D case
Conclusion
GTS NXConclusion
• In 3D models it is possible to review in detail the stress distributions oncross-sections, which is not possible in 2D models. Give more accurate and less conservative results.
• Failure surfaces need not be assumed with SRM.
• Failure takes place when the shear strength of the soil is less than the shear stress due to the internal and external loads on the soil.
• The finite element method does not require the data or concept of slices and satisfies the equilibrium state until failure.
• Stresses, deformations and stability of the excavation sequences can be obtained through construction stage analysis.
Integrated Solver Optimized for the next generation 64-bit platform
Finite Element Solutions for Geotechnical Engineering
Questions?https://midassupport.jitbit.com/helpdesk/KB
a.martinez@midasit.com
Recommended