em2004 geosim presentation

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9/7/ 2004 Penumadu, Prashant, and Frost. EM-2004 1

A VIRTUAL TRIAXIAL COMPRESSION

TEST SIMULATOR

Dayakar Penumadu: Department of Civil and Environmental

Engineering, University of Tennessee, Knoxville, TN, USAAmit Prashant: Department of Civil and Environmental

Engineering, University of Tennessee, Knoxville, TN, USA

David J. Frost: Department of Civil and Environmental

Engineering, Georgia Institute of Technology, Atlanta, GA, USA

Acknowledgements: Financial support from the National Science Foundation (NSF)

through grants EEC-0296187 is gratefully acknowledged. Any opinions, findings, and

conclusions or recommendations expressed in this material are those of authors and do

not necessarily reflect the views of NSF.


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9/7/2004 Penumadu, Prashant, and Frost. EM-2004 2

Presentation Outline

Concept of Virtual Laboratory Testing

Teaching and Learning Styles Limitations to Existing Pedagogy

Potential Benefits from Geo-Sim

Role of Constitutive Models / Data Base Examples / Screen Shots

Summary


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Concept of Virtual Laboratory Testing

1. The objective of this research is to develop multimedia software (Geo-Sim) for performing virtual laboratory experiments to complement and

extend the existing laboratory course component related to soil behavior.

The virtual experiments are proposed as an addition to the limited realexperiments performed within the existing curriculum.

2. For virtual experiments, well-trained neural network based soil models and

digitized data are being used to simulate the response of geo-materials in a

variety of Geotechnical laboratory tests and under a range of testconditions.

3. The proposed test simulator will contain modules consisting of different

laboratory simulations. A pilot triaxial compression test module within the

test simulator for evaluating the shear strength behavior of soil has beendeveloped to date. The software supports WINDOWS platforms withmultimedia capabilities.

4. The Geo-Sim software will be implemented for evaluation starting in Fall,

2004 at the University of Tennessee, Knoxville.


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Use of Virtual Laboratory Testing

1. We have implemented a

preliminary virtual laboratory

environment using (YourLabs Package developed at

the University of Arizona)

2. The goal of our project is to

concentrate on Shear StrengthTesting Modules (as opposed

to introductory soil mechanics

experiments)

3. Feed-back from students is

proving to be very useful for

the development of Geo-Sim.


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Objective of Virtual Laboratory Testing

To overcome the current limitations in achieving the

goal of providing the student engineer with a goodknowledge of experimental apparatus, test procedure,

interpretation, and errors associated with the

measurement techniques. Related information on

instrumentation, specimen preparation, assembly, and

testing is provided using multi-media capabilities

using short and relevant video/audio clips. The Geo-

Sim interface also provides opportunities for studentsto perform virtual experiments to study parameter

effects.


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Cone of Learning and Need for Simulations


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Learning and Teaching Styles

In co-operation with faculty in liberal studies, the investigators

have been using Kolbs learning style inventory approach (Kolb,

1984) in evaluating the predominant learning styles of theundergraduate students in the soil mechanics class. A typical

summary of results of the survey indicate that the civil

engineering students can be categorized as convergers or

assimilators regarding their preferred learning style. The

implications of these learning styles are widely published (Felder

and Stice, 1992). These results in conjunction with the cone of

learning indicate that simulating the real experience becomes animportant learning aspect of a typical geotechnical student. Thus,

the laboratory simulations that Geo-Sim provides will be

especially useful for promoting their understanding.


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The advantages of the Test simulator

1) They provide the students with a realistic feel for magnitudes and

sensitivity to system parameters and allow them to examine the relationshipbetween such parameters

2) Hands-on laboratory experience is restricted to systems which are

relatively inexpensive and offer no safety problems and the simulations can

extend this experience to a wide range of experiments,3) Computer-assisted methods provide the undergraduates with interactive

design experiences which are relevant to their future careers

4) Experimental results (Mosterman et al., 1994) indicate that students who

use the virtual laboratory prior to a physical laboratory are able to completethe tasks in a shorter period of time with less assistance and are moresatisfied with the lab experience.


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Learning Objectives for Drained Triaxial Testing-

Example

To provide the student engineer with a good knowledge of:

1) Triaxial Apparatus

2) The Test procedure

3) Measured and Interpreted Data

4) Data Analysis

5) Interpreted Soil Behavior

Expose Possible Errors Involved With Measurement and

Assumptions With Interpretation


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Role of Constitutive Models in Virtual Experiments

1. Neural Network Models: Composed of many nonlinear computational

elements operating in parallel and arranged in patterns reminiscent of

biological neural nets. The approach used in this research was to represent

the experimentally observed behavior of soils within a unified

environment using neural networks. The soil behavior network is built

from experimental data using the organizing capabilities of the neural net,

i.e the network is presented with the experimental data and is trained to

learn the relationship between input and output variables for varyingcontrolling factors. The appropriate ANN computer code is linked to the

Geo-Sim program during the simulation phase for a given set of input

parameters associated with a specific laboratory test. Important limitation

is that to develop reliable ANN models, large amount of experimentaldata is required for training and validation and thus only those stress paths

that have large published data use ANN approach for generating virtual

response that is representative of real response.


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Role of Constitutive Models in Virtual Experiments

2. Digitization and Data Base: For those stress paths that have limited data

and use of neural nets is not reliable. Thus the virtual response is based

on using Graphical User Interface of Geo-Sim with appropriate link with

the Data Base capabilities of the code. In order to increase the capabilities

of the GEOSIM program, a database was developed to store the soil test

parameters used in developing the simulation parameters. The purpose of

the database is to facilitate querying and visualizing soil test parameters

and results as well as provide continuous support for adding new soil testdata into the database without requiring additional code to be written

within GEOSIM. Once, soil test data has been added, the software can

retrieve the data based on queries coded into the GUI. Alternatively,

users could generate queries of their own within the Microsoft Accessdatabase.


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Main Window


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Understanding of Various Phases of Testing

and Required Computations


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Simulation of Triaxial Drained Test


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Visualization and Analysis of Simulation

Data


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Report Generation


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Parametric Study


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Resources

Testing Equipment and its Components

Sampling techniques Sensors

Test Procedures

Error Sources and Limitations

Background Material (Soil Classification)

Data Analysis (More Comprehensive)

Audio Visual Resources (Ex. Sensors, Load Frame)


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Summary

Simulation of laboratory testing as a supplement to actual testingshows promise considering the learning styles of student engineers.

A multimedia software GeoSim is being developed that will

complement and extend the existing laboratory course componentrelated to consolidation and shear behavior of soils.

The software is designed such that the testing components aremodular in nature and the GUI provides easy navigation through

various modules/segments. Students can simulate various phases of testing and learn about the

assumptions, errors, and computations involved in each step byfacing a series of online questions.

The user can perform parametric study and use the availabledatabase of published experimental data for further analysis.

Details of the test apparatus, sampling, testing procedure, and otheruseful information is provided in the resources including many audio-visuals.

em2004 geosim presentation

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