PERMFILE46940

• Permit No: C1980001
• IBM Index Class Name: Permit File
• Doc Date: 12/11/2001
• Doc Name: SCS Technical Note No. 25, Appendix A
• Section_Exhibit Name: 4.3 Appendix 4.3-A
• Media Type: D
• Archive: No

6-97
Appendix A
•
Lane reports:
Critical tractive stress, Tc = 6 dm; where dm is in feet and
Tc is in psf.
This critical tractive stress is nearly identical with Shield's work for
d > k inch.
m
Lane recommends:
Allowable tractive stress, Tall 4.8 dm; dm, Tc same rmits as above.
This allowable tractive stress is conservative with respect to Shield's
work for dm > 4 mm and gives results identical to those from Eq. 6-S of
TR-25.
Report 108 reports:
Critical tractive stress, tc = 5 dm; dm, tc same units as above.
This critical tractive stress is conservative with respect to Shield's
work ford > 4 mm.
m
• Report 108 recommends:
Allowable tractive stress, Tall = 4 dm; dm, tc same units as above.
Th:s allowable tractive stress is conservative with respect to Shield's
work for dm > 2 mm and gives results identical to those from Eq. 24 of
TR-59, setting the FS value equal to 1 and using the default value for
Cso•
For armoring design analysis, the characteristic armor particle size
(dm) is chosen from the coarser portion of the original material since
most of the fine material will be hydraulically removed. Usually dID duo;
therefore, m 90. Furthermore, for design purposes, all material
sr~~aller than the dm is assumed to be sorted out. Therefore, the depth
o° degradation (Dd) is
Dd dm/[(100 - m)/100] = 10 d90 (see page b-31).
This assumption has a physical interpretation. The dyo size of the
original bed material (before armoring) will became the dso of the final
• exposed surface bed material (after armoring).