Page 119 - Geotechnical Engineering Soil and Foundation Principles and Practice

The Soil Profile
114 Geotechnical Engineering

the place where the series has been described and mapped. Examples are the
Mankato series, named after Mankato, Minnesota; and the Hilo series named after
Hilo, Hawaii. After a soil has been described and named, that name is applied to all
soils having essentially the same weathering profile and genetic history.

A soil series represents a single solution to eq. (5.1); that is, all soils within a series
have the same number of horizons of similar depth, developed under the same
climate and same kinds of vegetation, with essentially the same slope and landscape
factors, from the same kind of parent material, and of approximately the same age.
An allowable range is included in each of the factors, but the consistency is
sufficient to allow assignment of a particular soil to a particular series. As one soil
series will intergrade into another, analyses are made to define cutoff points.

5.6.3 Soil Association Areas
Soil series that dominate or characterize a particular area define a soil association
area. Block diagrams showing soil association areas are included in county soil
survey reports and are useful for visualizing and interpreting soils in a given area.
A representative block diagram is shown in Fig. 5.7.

Figure 5.7
Block diagram showing topographic relationships of soil series in a soil association area where the
parent materials are glacial till and slope wash deposits. Alfisols are developed under forest and
Mollisols under grass. ‘‘UD’’ in the suborder designation stands for a humid climate, and ‘‘AQU’’ for
wet conditions. The latter series also have expansive clay minerals concentrated in their B horizons.
(USDA.)

Downloaded from Digital Engineering Library @ McGraw-Hill (www.digitalengineeringlibrary.com)
Copyright © 2007 The McGraw-Hill Companies. All rights reserved.
Any use is subject to the Terms of Use as given at the website.