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1.1 Purpose and Application:
1.1.1 This guide summarizes the equipment, field procedures, and
interpretation methods for the assessment of subsurface conditions
using the gravity method.
1.1.2 The gravity method described in this guide is applicable to
investigation of a wide range of subsurface conditions.
1.1.3 Gravity measurements indicate variations in the earth's
gravitational field caused by lateral differences in the density of
the subsurface soil or rock or the presence of natural voids or
man-made structures. By measuring spatial changes in the
gravitational field, variations in subsurface conditions can be
determined.
1.1.4 Detailed gravity surveys (commonly called microgravity
surveys) are used for near-surface geologic investigations and
geotechnical, environmental, and archaeological studies. Geologic
and geotechnical applications include location of buried channels,
bedrock structural features, voids, and caves, and low-density
zones in foundations. Environmental applications include site
characterization, ground water studies, landfill characterization,
and location of underground storage tanks (1).
1.2 Limitations:
1.2.1 This guide provides an overview of the gravity method. It
does not address the details of the gravity theory, field
procedures, or interpretation of the data. Numerous references are
included for that purpose and are considered an essential part of
this guide. It is recommended that the user of the gravity method
be familiar with the references cited and with the Guides D 420, D
5753, D 6235, and D 6429, and Practices D 5088, and D 5608.
1.2.2 This guide is limited to gravity measurements made on land.
The gravity method can be adapted for a number of special uses: on
land, in a borehole, on water, and from aircraft and space. A
discussion of these other gravity methods, including vertical
gravity gradient measurements, is not included in this guide.
1.2.3 The approaches suggested in this guide for the gravity method
are the most commonly used, widely accepted, and proven. However,
other approaches or modifications to the gravity method that are
technically sound may be substituted.
1.2.4 This guide offers an organized collection of information or a
series of options and does not recommend a specific course of
action. This document cannot replace education, experience, and
should be used in conjunction with professional judgment. Not all
aspects of this guide may be applicable in all circumstances. This
ASTM document is not intended to represent or replace the standard
of care by which the adequacy of a given professional service must
be judged, nor should this document be applied without
consideration of a project's many unique aspects. The word
"Standard" in the title of this document means only that the
document has been approved through the ASTM consensus process.
1.3 Precautions:
1.3.1 It is the responsibility of the user of this guide to follow
any precautions in the equipment manufacturer's recommendations and
to establish appropriate health and safety practices.
1.3.2 If this guide is used at sites with hazardous materials,
operations, or equipment, it is the responsibility of the user of
this guide to establish appropriate safety and health practices and
determine the applicability of any regulations prior to use.
1.3.3 This guide does not purport to address all of the safety
concerns, if any, associated with the use of the gravity method. It
is the responsibility of the user of this guide to establish
appropriate safety and health practices and to determine the
applicability of regulations prior to use.
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