Modelling Magma Intrusion into an Underground Opening

Presentation to

VOLCANIC ERUPTION MECHANISM MODELING WORKSHOP

November 14-16, 2002

University of Hew Hampshire

Durham, NH 03824, USA

Ed Gaffney and Rick RauenzahnLos Alamos National Laboratory, Los Alamos, NM 87545, USA

Modelling Magma Intrusion into an Underground Opening

Context of Yucca Mountain (Ed)–Geologic Setting–Repository Requirements–Potential Igneous Events–Goals of Modelling

CFDLIB (Rick)–Background and Basics–Version 02.1

•Volatile exsolution•Variable viscosity

Early results (Ed)–Initial Interactions–Effusive Flow

Context of Yucca Mountain

Geologic Setting– Fault block in rhyolitic tuff sequence

• Tertiary• Water table ~600 m,repository ~300 m

– Pliocene to Pleistocene basaltic eruptions• Closest (Lathrop Wells Cone) is 75 ka• ~0.15 km3

• Alkali basalt, 2-4 wt/o water

Context of Yucca Mountain

Repository Requirements– Exposure of target population

• Over 10,000 year span

– Potential hazards • Ground water seepage• Damage to waste packages from seismic activity• Volcanic intrusion

Context of Yucca Mountain

Potential Igneous Events– Unlikely (10-8 per year)– Intrusive/extrusive event similar to Lathrop wells

• alkali basalt• 1-4% (wt) H2O• ~0.1 km3

– Dike intersects drifts, damages waste packages• gas corrosion• heat effects on integrity• Impact, drag

– May erupt to surface• fissure, conduit, or dogleg

Context of Yucca Mountain

Goals of Modelling– Determine environment seen by waste packages

• Is there a shock from first eruption into drift?• Will magma fill drift?• Size and velocity of projectiles?• Peak environments (P, T, u, dynamic pressure) along drift• “Final” environments

– Evaluate mechanisms for release• Impacts of bombs, other fragments• Heating internal gas P rises rupture• Drag effects (carried to surface, torn by diff. drag forces, ...)

CFDLIB Background

• Multiphase compressible and incompressible flows– 10 years in development– Test bed for models– Applications in industry, defense

• Collocated (cell-centered) variables– Fluxing velocities are time-space advanced with pressure

correction

• ICE/MAC– Pressure waves treated implicitly (relax SS Courant

condition)– Advection/viscosity explicit– General EOS, multiphase exchange laws (user)

CFDLIB Background (cont’d)

• Particle-in-cell method– Allows mixed Lagrangian/Eulerian treatment– State variables (m, U, x, , …) kept on particles

that move with interpolated velocity– Fluid/structure interaction (history-dependent

stress laws)

• Example with rod penetrator

CFDLIB Background Elastic Rod Penetrator

CFDLIB Background Brittle Rod Penetrator

CFDLIB Background YMP special needs

• Vapor/magma equilibrium– Papale (1997, 1999)– Include air (extend K/J EOS by assuming ideal air)

• Variable (high) viscosity– Implicit treatment– Model of Shaw (1972)

• Generalized effective drag/heat transfer– Particle size/coefficients as f(k,Tk,...)

• Equations of state for gas (BKW) and liquid(Us-Up)

Early ResultsMagma /Tunnel Interaction

Early ResultsMagma /Tunnel Interaction

X

Y

0 200 400 6000

250

500

P130.0

60.328.013.0

6.02.81.3

N = 1296

Frame 001 10 Sep 2002 FLIPICE: Blast wave from steam-filled maFrame 001 10 Sep 2002 FLIPICE: Blast wave from steam-filled ma

Early ResultsGas Jet

A 20 bar gas jet expands into an atmosphere

X

Y

0 500 10000

100

200

300

400

500

600

700

800

900

1000

1100

1200

V87.6081.2974.9768.6662.3456.0349.7143.4037.0830.7724.4518.1411.83

5.51-0.80

CFDLIB 99.2

T = 1.000E+03N = 27061

Frame 001 17 Oct 2002 FLIPICE: Blast wave from steam-filled maFrame 001 17 Oct 2002 FLIPICE: Blast wave from steam-filled ma

Conclusions

• Goal: model magma drift interaction

• CFDLIB is multifluid, multiphase code• Mixed Lagrangian/Eulerian facilitates fluid-structure interaction• Implicit treatment of pressure waves• User supplied equation of state and exchange laws• Volatile equilibrium with silicate liquid like Papale but with different equation of state• Variable (high) viscosity

• Work has just begun and team is small• magma expansion into drift• effusive flow in drift (~ lava tube)• gas jet from a circular vent