Page 283 - Geotechnical Engineering Soil and Foundation Principles and Practice

Soil Consistency and Engineering Classification
278 Geotechnical Engineering

12.6. The liquid limit of a soil is 69% and its natural moisture content is 73%.
Is this soil stable, metastable, or unstable? What is the dictionary
definition of metastable?
12.7. Define shrinkage limit and shrinkage ratio.
12.8. The volume of the dish used in a shrinkage limit test is measured and
3 3
found to be 20.0 cm , and the volume of the oven-dry soil pat is 14.4 cm .
The weights of the wet and dry soil are 41.0 and 30.5 g, respectively.
Calculate the shrinkage limit and shrinkage ratio.
12.9. Describe a nonplastic soil and explain how this characteristic is
determined in the laboratory.
12.10. Distinguish clearly between a nonplastic soil and one that has a PI equal
to zero.
12.11. Can you think of a reason why a fine-grained binder soil should be close
to or below the plastic limit when it is added to a coarse-grained soil to
form a stabilized soil mixture?
12.12. If the PI of a stabilized soil pavement is too high, what adverse
characteristics are likely to develop under service conditions? What may
happen if the PI is too low?
12.13. Is soil containing water in excess of the liquid limit necessarily a liquid?
Explain.
12.14. A soil clod coated with a semipermeable plastic membrane and
equilibrated at 1/3 bar moisture tension weighs 210 g in air and 48 g
submerged in water. After oven-drying, the corresponding weights
are 178 g and 47 g. (a) What is the COLE? (b) Rate the expansive
potential of this soil. (c) If you have no choice but to put a light
slab-in-grade structure on the soil, what precautions might be taken
to prevent damage?
12.15. What is the significance of the group index in connection with the
AASHTO system of classification?
12.16. State the broad general character of soils included in groups A-1,
A-2, and A-3 of the AASHTO system and give approximate equiv-
alents in the Unified Classification system. What are the specific
differences?
12.17. What are the principal differences between two soils classified as A-4
and A-5 in the AASHTO system?
12.18. What are the approximate Unified Classification equivalents of AASHTO
groups A-4, A-5, A-6, A-7, and A-8? Which pairs are most nearly
identical?
12.19. Give the major characteristics of soils included in (a) the GW, GC, GP,
and GF groups of the Unified Classification system; (b) the SW, SC, SP,
and SF groups; (c) the ML, CL, and OL groups; (d) the MN, CH, and OH
groups.

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