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Publication Number: FHWA-HRT-04-095
Date: November 2004

Manual for LS-DYNA Soil Material Model 147

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Federal Highway Administration
Research and Development
Turner-Fairbank Highway Research Center
6300 Georgetown Pike
McLean, VA  22101

Foreword

This report documents a soil material model that has been implemented into the dynamic finite element code, LS-DYNA, beginning with version 970. This material model was developed specifically to predict the dynamic performance of the foundation soil in which roadside safety structures are mounted when undergoing a collision by a motor vehicle. This model is applicable for all soil types when one surface is exposed to the elements if the appropriate material coefficients are inserted. Default material coefficients for National Cooperative Highway Research Program (NCHRP) Report 350, Strong Soil, are stored in the model and can be accessed for use.

This report is one of two that completely documents this material model. This report, Manual for LS-DYNA Soil Material Model 147 (FHWA-HRT-04-095), completely documents this material model for the user. The second report, Evaluation of LS-DYNA Soil Material Model 147 (FHWA-HRT-04-094), completely documents the model's performance and the accuracy of the results. This performance evaluation was a collaboration between the model developer and the model evaluator. Regarding the model performance evaluation, the developer and evaluator were unable to come to a final agreement regarding the model's performance and accuracy. (The material coefficients for the default soil result in a soil foundation that may be stiffer than desired.) These disagreements are listed and thoroughly discussed in section 9 of the second report.

This report will be of interest to research engineers associated with the evaluation and crashworthy performance of roadside safety structures, particularly those engineers responsible for the prediction of the crash response of such structures when using the finite element code LS-DYNA.

 

Michael F. Trentacoste
Director, Office of Safety
Research and Development

Notice

This document is disseminated under the sponsorship of the U.S. Department of Transportation in the interest of information exchange. The U.S. Government assumes no liability for the use of the information contained in this document.

The U.S. Government does not endorse products or manufacturers. Trademarks or manufacturers' names appear in this report only because they are considered essential to the objective of the document.

Quality Assurance Statement

The Federal Highway Administration (FHWA) provides high-quality information to serve Government, industry, and the public in a manner that promotes public understanding. Standards and policies are used to ensure and maximize the quality, objectivity, utility, and integrity of its information. FHWA periodically reviews quality issues and adjusts its programs and processes to ensure continuous quality improvement.

1. Report No.
FHWA-HRT-04-095

2. Government Accession No.

3. Recipient's Catalog No.

4. Title and Subtitle
 Manual For LS-DYNA SOIL MATERIAL MODEL 147

5. Report Date
November 2004

6. Performing Organization Code

7. Author(s)
Brett A. Lewis, Ph.D.

8. Performing Organization Report No.

9. Performing Organization Name and Address
APTEK, Inc.
1257 Lake Plaza Drive
Colorado Springs, CO 80906

10. Work Unit No. (TRAIS)

11. Contract or Grant No.
DTFH61-96-C-00071

12. Sponsoring Agency Name and Address
Volpe National Transportation Systems Center
55 Broadway, Kendall Square
Cambridge, MA 02142-1093

Federal Highway Administration
6300 Georgetown Pike
McLean, VA  22101-2296

13. Type of Report and Period Covered
Final Report
09-28-1998 through 08-31-2004

14. Sponsoring Agency Code

15. Supplementary Notes
Contracting Officer's Technical Representative (COTR): Martin Hargrave, Office of Safety Research and Development, HRDS-04, Turner-Fairbank Highway Research Center

16. Abstract

This is the final report for the development of the Federal Highway Administration’s (FHWA’s) soil model implemented into LS-DYNA. This report is in three sections: (1) the research plan, which describes the justification and the detailed theory of the model; (2) the user’s manual that was submitted to Livermore Software Technology Corporation (LSTC) for inclusion in the LS-DYNA user’s manual; and (3) examples that show the expected results of the model.

The companion report to this manual is: 

Evaluation of LS-DYNA Soil Material Model 147 (FHWA-HRT-04-094).

17. Key Words
Soil, LS-DYNA, shear, elastic, plastic, damageroadside safety

18. Distribution Statement
No restrictions.  This document is available to the public through the National Technical Information Service, Springfield, VA 22161.

19. Security Classification (of this report)
Unclassified

20. Security Classification (of this page)
Unclassified

21. No. of Pages
68

22. Price

Form DOT F1700.7 (8-72)  Reproduction of completed page authorized


Preface

The goal of the work performed under this program, Development of DYNA3D Analysis Tools for Roadside Safety Applications, is to develop soil and wood material models, implement the models into the LS-DYNA finite element code, and evaluate the performance of each model through correlations with available test data .(1)

This work was performed under Federal Highway Administration (FHWA) Contract No. DTFH61-98-C-00071. The FHWA Contracting Officer's Technical Representative (COTR) was Martin Hargrave.

Two reports are available for each material model. One report is a user's manual, Manual for LS-DYNA Soil Material Model 147; the second report is a performance evaluation, Evaluation of LS-DYNA Soil Material Model 147.(2) The user's manual thoroughly documents the soil model theory, reviews the model input, and provides example problems for use as a learning tool. The performance evaluation for the soil model documents LS-DYNA parametric studies and correlations with test data performed by a potential end user of the soil model, along with commentary from the developer. The reader is urged to review this user's manual before reading the evaluation report. A user's manual(3) and evaluation report(4) are also available for the wood model.

The model developer and evaluator were unable to come to a final agreement regarding several issues associated with the model's performance and accuracy during the second independent evaluation of the soil model. These issues are listed and thoroughly discussed in section 9 of the soil model evaluation report.(2)

SI* (Modern Metric) Conversion Factors


Table of Contents

CHAPTER 1. THEORY MANUAL

CHAPTER 2. USER'S MANUAL

CHAPTER 3. EXAMPLES MANUAL

CHAPTER 4. SUMMARY

APPENDIX A. DETERMINATION OF PLASTICITY GRADIENTS

APPENDIX B. EXAMPLES OF INPUT

REFERENCES

List of Figures

Figure 1. (a) Pressure-dependent (Mohr-Coulomb) and (b) pressure-independent (Von Mises) yield surfaces
Figure 2. Yield surface in deviatoric plane for cohesionless soils.
Figure 3. Principal stress difference (peak shear strength) versus pressure (average normal stress) for road-base material
Figure 4. Force deflection for two steel posts in soil tests with different moisture contents (5 percent and 26 percent)
Figure 5. Energy versus deflection for two steel posts in soil bogie tests with different moisture contents
Figure 6. Model 25 single-element run, triaxial compression at 3.4 MPa compared to WES data
Figure 7. Pressure versus volumetric strain showing the effects of the D1 parameter
Figure 8. Standard Mohr-Coulomb yield surface in principal stress space.
Figure 9. Comparison of Mohr-Coulomb yield surfaces in shear stress— Pressure space (standard-(A)/green, modified-(B)/red)
Figure 10. Yield surface with e = 0.55.
Figure 11. Effects on pressure because of pore-water pressure.
Figure 12. Effects of parameters on pore-water pressure.
Figure 13. Principal stress difference versus principal strain difference for triaxial compression test at s2 = 6.9 MPa of WES road-base material
Figure 14. Hardening of yield surface.
Figure 15. Principal stress difference versus axial strain for triaxial compression test at s2 = 6.9 MPa of WES road-base material
Figure 16. Definition of the void formation parameter.
Figure 17. Zeta versus strain rate for different parameters.
Figure 18. Elastic moduli and undamaged stresses.
Figure 19. Elastic trial stresses
Figure 20. Determination of plastic strains
Figure 21. Update of stresses and history variables
Figure 22. Viscoplasticity update
Figure 23. Damage update
Figure 24. Pressure versus volumetric strain showing the effects of the D1 parameter
Figure 25. Effects on pressure caused by pore-water pressure.
Figure 26. Effects of D2 and Ksk parameters on pore-water pressure.
Figure 27. Z-stress versus time for single-element 3.4-MPa triaxial compression simulation
Figure 28. LS-DYNA model of direct shear test DS-4.
Figure 29. Shear stress versus deflection comparison for DS-4.
Figure 30. Analysis results for DS-4 deformation.
Figure 31. Simple two-material shear model.
Figure 32. Deformed shape of 1 gauss point element analysis.
Figure 33. Deformed shape of 8 gauss point element analysis.
Figure 34. Comparison of x-y stress at element 115 for 1 gauss point and 8 gauss point elements

List of Tables

  1. Gradation data for USACE road-base soil tests

  2. Input parameters for soil model

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