Lesson 3/Learning Event 2
WHAT TO INCLUDE ON A BORING LOG
Depth below ground surface.
Elevation of soil layers and ground water table.
Thickness of layers.
Graphical symbol of the soil type.
Description of soil.
Position where soil sample is taken; whether disturbed or undisturbed.
Natural moisture content, in percent of dry weight of soil.
Number of blows of a 140-pound or 300-pound hammer falling 30 inches to penetrate a 2-inch
diameter sampling device or a casing one foot into soil.
Notes indicating position of ground water table, encountered tree roots, or other pertinent facts.
Title of the project, job and/or contract number.
Location of the project.
Surface elevation of the boring.
Name of the foreman in charge of drilling.
The type of tools used in making the boring should be recorded. If the tools were changed, the depth at
which the change was made and the reason for change should be noted. Incomplete or abandoned
borings should be described with no less care than successfully completed drill holes. The notes should
contain everything of significance observed on the job, such as the elevations at which wash water was
lost from the hole.
The information contained in the field notes should be assembled in the form of boring logs in which the
boundaries between the strata are plotted at their correct elevation on a suitable vertical scale.
THE SOIL PROFILE
The engineer keeps detailed field logs of all auger borings or test pits made during the soil survey.
When the survey has been completed, the information contained in the separate logs is consolidated. In
addition to the classification and depth of soil layers encountered in each log, it is desirable to show the
natural water contents of fine-grained soils along the side of each log when possible as shown in Figure
25. Also the elevation of the ground water table should be noted. The elevation is determined during
the soil survey by observing the level at which free water stands in the test holes. To get an accurate
determination, holes should be covered and inspected 24 hours after being dug, in order to allow the
water to reach maximum level. The soil profile shown in Figure 26 is a graphical representation of a
vertical cross-section of the soil layers from the surface of the earth downward. It shows the location