Environmental Engineering Reference
In-Depth Information
TABLE 6.14
Description of a Weathering Profile in Igneous and Metamorphic Rocks
a
Zone (class)
Description
RQD(%)
Core recovery
Relative
Relative Strength
(%)
Permeability
Residual soil
A Horizon
Top soil, roots. Zone of leaching and eluviation may be porous
—
0
Medium to high
Low to medium
B Horizon
Usually clay-enriched with accumulations
—
0
Low
Commonly low, high if
of Fe, Al, and Si. Hence may be cemented,
cemented
no relict structure present
C Horizon
Relict rock structure retained. Silty grading
0
0-10
Medium
Low to medium (relict
(saprolite)
to sandy material. Less than 10%
structure very significant)
corestones. Often micaceous
Weathered rock
Transition
Highly variable, soil to rocklike. Commonly
0-50
10-90
High (water
Medium to low where
c-f sand, 10 to 95% corestones. Spheroidal
losses common)
weak or relict structures
weathering common
present
Partly weathered
Soft to hard rock joints stained to altered.
50-75
90
Medium to high
Medium to high for intact
rock
Some alteration of feldspars and micas
specimens
Unweathered rock
No iron stains to trace along joints. No
75 (generally
Generally 100
Low to medium
Very high for intact
weathering of feldspars and micas
90)
specimens
Note
:
The specimens provide the only reliable means of distinguishing the zones.
a
From Deere, D.U. and Patton, F.D.,
Proceedings of the 4th Panamerican Conference Soil Mechanics and Foundation Engineering,
San Juan, Vol. 1, 1971, p. 87.
