1705 1530 1615 introduction 3d tunnel

CG1 Chile May 15-18, 2006: Introduction to Plaxis 3D Tunnel 1

PLAXIS FINITE ELEMENT CODE FOR SOIL AND ROCK ANALYSES

Tunnels in Plaxis

Dennis WatermanPlaxis BV


Tunnel designer

Full tunnel

Half tunnel -left part

Half tunnel -right part



Shield tunnel

• Geometry construction• Select tunnel shape (half or whole tunnel)• Select option “bored tunnel”• Contraction model:

• Activate shell and interface to model tunnel lining

• For grout pressure model: • Activate shell and interface to model TBM• Use thickness to model tunnel lining with volume

elements


Shield tunnel

Contraction model• First phase

• Activation of tunnel lining• Excavation of soil inside tunnel• Dewatering (make tunnel clusters dry)

• Second phase• Apply contraction

• Method to simulate soil volume loss outside tunnel• Mostly used for shield tunnelling• Input and activation via staged construction



Shield tunnelGrout pressure model

• First phase• Activation of TBM• Excavation of soil inside TBM• Dewatering (make tunnel clusters dry)

• Second phase• Applying small contraction to model cone shaped TBM

• Third phase• Switch off TBM• Apply grout pressure

• Fourth phase• Remove grout pressure• Install final lining


NATM tunnel

• Geometry construction• Select tunnel shape (half or whole tunnel)• Select option “NATM tunnel”• Start to enter radius and angle of first section• Select second section• Repeat this for all sections • Activate shell and interface for section

independently when needed



NATM tunnel

β -method• First phase

• Deactivate tunnel clusters without activating of lining and calculate using ΣMstage = 1 - β (Staged Construction, Advanced)

• Second phase• Activate tunnel lining and continue calculation

until ΣMstage = 1


Plaxis 3D Tunnel

Dennis WatermanPlaxis BV



Content

• General remarks about 3D models• Creation of a 3D model

• Procedure• Geometry input• Calculations• Output and visualisation

• Examples• Conclusions


General remarks about 3D models

• Requires long calculation time and much computer memory• Find balance between accuracy and

calculation time• Requires patience and understanding of

users• Becomes practically applicable



Creation of a 3D model

• Procedure• 2D modelling of cross

section plane• 2D mesh generation of cross

section model• 3D extension in third

direction (‘z-planes’ and ‘slices’)

• Staged construction and excavation of geometry parts per plane or slice

Cross section plane

2D mesh3D mesh

y

xz



• ‘Planes’ and ‘Slices’

slices

z-planes

rear plane

front plane

z

y

x




• Geometry-input• Like in PLAXIS 2D• 3D extension via z-planes:• 15-noded wedge elements

(comparable with 6-noded el. in 2D)



• Calculations• All phases defined by means of Staged Construction• Indicate per ‘slice’ or ‘plane’:

• (De)activation of soil and structures• Changing material data sets• (De)activation of loads• Contraction• Volume strain• (water) pressure

• Top view option• Full 3D preview






• Output and visualisation• Visualisation in full 3D and in 2D cross

sections• Separate output for structural elements • Partial geometry option (looking iniside

model)





Example

• Second Heinenoord Tunnel (shield Tunnel)

ID Type g_unsat g_sat nu E_ref c' phi psi K0 [kN/m3] [kN/m3] [ - ] [kN/m2] [kN/m2] [ ° ] [ ° ] [-]0B Drained 16.5 17.2 0.34 3900 3.0 27.0 0.0 0.580A Undrained 16.5 17.2 0.34 3900 3.0 27.0 0.0 0.583 Drained 19.5 19.5 0.30 19300 0.0 35.0 5.0 0.472 Drained 19.0 19.0 0.31 18500 0.0 33.0 3.0 0.4718 Drained 20.5 20.5 0.30 29600 0.0 36.5 6.5 0.4532 stiff Drained 20.5 20.5 0.30 444000 0.0 36.5 6.5 0.5038 stiff Undrained 20.0 20.0 0.32 119000 7.0 31.0 1.0 0.5538F stiff Drained 21.0 21.0 0.30 593000 0.0 37.5 7.5 0.56



Example

14 x 3m

8.5m

10.5m


Example

• Phases:• TBM advances one slice (3m) in every

phase• TBM front: face pressure• TBM tail: Contraction 0.5%• Between TBM and lining: Groutpressure,

jack forces• Application of lining



Example

Deformed mesh




Conclusions

• 3D calculations are time consuming, but become practically applicable.

• Perform only 3D calculations if really necessary

• Take care of the following aspects:• Choice of soil models and parameters• Mesh fineness (coarseness)• Calculation phases (construction stages)

1705 1530 1615 introduction 3d tunnel

Documents

tunnel dewatering

model tunnel lining

tunnel shape half

option natm tunnel

d extension

rock analysescreation

rock analysesplaxis

rock analysestunnels