Environmental Engineering Reference
In-Depth Information
150
Types C
CD and L
S
ED
E
140
10
130
120
15
110
20
100 0
25
1
2
3
4
5
6
7
8
9
10
11 12
Range of grain sizes C r , in units of soil fractions
(b) Approximate Minimum Densities, 0% D r
Decrease in Density (pcf)
Range in grain sizes ( C r )
Coarser soils
Finer soils
1
3
10
to
to
20
3
5
5 and greater
20
25
25
30
+
to
(c) Approxomate Influence of Grain Shape on Density
FIGURE 3.10
Maximum compacted densities, approximate
minimum densities, and influence of grain
shape on density for various gradations.
(From Burmister, D. M., ASTM, Vol. 48,
Philadelphia, PA, 1948. Reprinted with
permission of the American Society for
Testing and Materials.)
Grain shape
Change in density (pcf)
Very angular
Subangular
Rounded or waterworn
0.5% mica
10 to 15
0 to normal
+2 to +5
2 to 5
C shapes have a high percentage of coarse and fine particles compared with sand
particles and are characteristics of some alluvial valley deposits in an arid cli-
mate where the native rocks are quartz-poor.
E and D shapes include a wide range of particle sizes characteristics of glacial
tills and residual soils.
Relationships
General relationships among gradation characteristics and maximum compacted densi-
ties, minimum densities, and grain angularity are given in Figure 3.10 (note the signifi-
cance of grain angularity). Gradation characteristics for soils of various geologic origins
(see Chapter 7), as deposited, are given in Figure 3.11.
Test Methods
Gradations are determined by sieve analysis (ASTM D422) and hydrometer analysis
(ASTM D422), the latter test being performed on material finer than a no. 200 sieve. For
sieve analysis, a specimen of known weight is passed dry through a sequence of sieves of
decreasing size of openings and the portion retained is weighed, or a specimen of known
weight is washed through a series of sieves and the retained material dried and weighed.
The latter procedure is preferred for materials with cohesive portions because dry sieving
is not practical and will yield erroneous results as fines clog the sieves.
 
Search WWH ::




Custom Search