CENTER FOR COMPUTATIONAL MATHEMATICS COLLOQUIUM
                  UNIVERSITY OF COLORADO AT DENVER


TITLE:   "Finite element modeling of random materials"

SPEAKER:  Vaughn Griffiths, Visiting Professor at Colorado School of Mines

DATE:    Wednesday, November 16, 1994

PLACE:   Math Conference Room - Suite 540
         UCD Building, 1250 14th St., Denver

TIME:    2:30 pm (Refreshments served at 2:15 pm)

ABSTRACT: This presentation brings together advanced random field generation 
and finite element techniques to model steady seepage problems in 2- and 
3-dimensions. The applications include classical problems of seepage beneath 
water retaining structures in which probabilistic issues relating to flow rates 
and exit gradients are examined. The influence of three-dimensionality is given 
particular emphasis and contrasted with results that are obtained using an 
idealized two-dimensional model.

The analyses treat the soil permeability as a spatially random property with
specified mean, variance and spatial correlation length. The value of
permeability assigned to each element is a local average of the lognormally
distributed random field and takes into account the element dimensions.
The influence of the spatial correlation or `scale of fluctuation' is given 
special consideration, since this aspect is not always included in probabilistic
geotechnical analysis. Monte-Carlo simulations are performed to establish 
statistics relating to the output quantities of interest.

The tool of analysis is the finite element method, which is naturally suited
to analyzing materials with properties varying over space.  For the 
computationally intensive 3-d studies, strategies are described for
optimizing the efficiency of the code in relation to memory and CPU
requirements.