Environmental Engineering Reference
In-Depth Information
Burmister System (ASEE)
The system provides a definitive shorthand nomenclature. Percentage ranges in weight
for various granular components are given as: AND,
50%; and, 35-50%; some, 20-35%;
little, 10-20%; trace, 1-10%. The percentages are estimated from experience, or by the use
of the “ball moisture test” (see Burmister, 1949; Table 5.36).
Silts and clays can be identified by the smallest diameter thread that can be rolled with
a saturated specimen as given in
Table 5.35.
An example sample description is ”Coarse to fine SAND, some fine gravel, little silt,” or
in shorthand nomenclature: ”c-f S, s.f G, 1. Si.” From field descriptions it is possible to con-
struct reasonably accurate gradation curves, as in the example given in
Figure 5.14,
which
have many applications (see
Section 3.2.3).
TABLE 5.36
Field Determination of Soil Components
a
Component
Characteristic
Determination
Gravel
Dia. 5-76 mm
Measurable
Sand
Coarse
Dia. 2-5 mm
Visible to eye, measurable
Medium
Dia. 0.4-2.0 mm
Visible to eye
Fine
Dia. 0.074-0.4 mm
Barely discernible to unaided eye
Silt: coarse
Dia. 0.02-0.074 mm
Distinguishable with hand lens
Sand-silt mixtures
Apparent cohesion
Measured by ball test (Burmister, 1949)
Form ball in hand by compacting moist soil to diameter
1½ in (37 mm)
Medium to fine sand forms weak ball with difficulty; cannot be
picked up between thumb and forefinger without crushing
Ball can be picked up with difficulty: 20% silt
Ball readily picked up: 35 to 50% silt
Silt vs. clay
Dia.
0.074 mm
See also
Table 5.37
Silt
Strength
Low when air-dried, crumbles easily
Dilatancy test
Mixed with water to thick paste consistency. Appears wet and
shiny when shaken in palm of hand, but when palm is cupped
and sample squeezed, surface immediately dulls and dries
Dispersion test
Mixed with water in container: particles settle out in ¼ to 1 h
Thread test
Rolls into thin threads in wet state but threads break when
picked up by one end
Clay
Strength
High when air-dried, breaks with difficulty
Plasticity
When mixed with water to form paste and squeezed In hand,
specimen merely deforms and surface does not change in
appearances
Dispersion test
Remains in suspension from several hours to several days in
container
Thread test
Can be rolled into fine threads that remain intact. Fineness
depends on clay content and mineralogy
Thread diameter when saturated vs. PI and identification
given in
Table 5.35
Adhesion
Sticky and greasy feel when smeared between fingers
Organic soils
Strength
Relatively high when air-dried
Odor
Decayed organic matter; gases
Organic matter
Root fibers, etc.
Shrinkage
Very high
a
See also ASTM D2488.
