Evaluation of LS-DYNA Soil Material Model 147

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APPENDIX A. INITIAL SOIL EXPERIENCE OF USER

The soil material model using the Nebraska soil parameters provided by the developer do not accurately simulate the physical testing (as shown in the following figures).

Figure 24. Soil modulus failure test.

Figure 25. Soil shear failure test.

APPENDIX B. VERIFICATION OF RESULTS ON DIFFERENT COMPUTER PLATFORMS

Using different computer platforms, a comparison of three different models using the FHWA soil model in LS-DYNA is made. Results from an Intel ^®-based PC (using Windows) are provided by both the developer and the user, while UNIX-based results from an SGI Octane ^® (using UNIX) are provided by the user.

The user's SGI results were obtained using LS-DYNA, Version 970 Beta, Revision 1812, June 7, 2002, for an SGI Workstation IRIX64 6.5.

The developer's PC results were obtained using LS-DYNA, Version 970 Beta, Revision 1812, June 7, 2002, for a PC (Intel) Windows 2000.

Although the results are shown to be different in the latter stages of the simulations on the different computer platforms, they appear to be within an acceptable range based on previous experience with using different computers.

SINGLE ELEMENT MODELS

Two single element models were run to check the consistency between the PC (Intel)-based computers and the SGI-based computers. Specific results for each model are described below. The developer supplied only the d3plot files from these runs; thus, the comparison is limited to the information stored in those files.

The deformed geometry of the single element models appeared to be the same and, thus, are not shown.

Model hydten1: Hydrostatic Tension

The internal energy for the hydrostatic tension runs are shown in figure 26. The results are nearly identical until 35 ms. After 35 ms, the results for the SGI and PC begin to diverge. There was no discernible difference between the developer's PC and the user's PC results. The difference between the SGI and PC results after 35 ms is attributed to the significant plasticity that the element has undergone after that time. Once plasticity becomes great enough, round-off errors between the computer platforms begin to influence the results. This, however, is only conjecture.

Figure 26. Hydrostatic tension: Internal energy.

Model txc3-4pr0c.k: Triaxial Compression

The internal energy and effective stress for the triaxial compression runs are shown in figures 27 and 28. The results are nearly identical, with the exception that the single element in the user's SGI run fails a few cycles before the PC runs.

Figure 27. Triaxil compression results: Internal energy.

Figure 28. Triaxial compression results: Effective stress.

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