ASTM D6430-99(2010)
(Guide)Standard Guide for Using the Gravity Method for Subsurface Investigation
Standard Guide for Using the Gravity Method for Subsurface Investigation
SIGNIFICANCE AND USE
Concepts—This guide summarizes the equipment, field procedures, and interpretation methods used for the determination of subsurface conditions due to density variations using the gravity method. Gravity measurements can be used to map major geologic features over hundreds of square miles and to detect shallow smaller features in soil or rock. In some areas, the gravity method can detect subsurface cavities.
Another benefit of the gravity method is that measurements can be made in many culturally developed areas, where other geophysical methods may not work. For example, gravity measurements can be made inside buildings; in urban areas; and in areas of cultural, electrical, and electromagnetic noise.
Measurement of subsurface conditions by the gravity method requires a gravimeter (Fig. 1) and a means of determining location and very accurate relative elevations of gravity stations.
The unit of measurement used in the gravity method is the gal, based on the gravitational force at the Earth's surface. The average gravity at the Earth's surface is approximately 980 gal. The unit commonly used in regional gravity surveys is the milligal (10−3 gal). Typical gravity surveys for environmental and engineering applications require measurements with an accuracy of a few μgals (10−6 gals), they are often referred to as microgravity surveys.
A detailed gravity survey typically uses closely spaced measurement stations (a few feet to a few hundred feet) and is carried out with a gravimeter capable of reading to a few μgals. Detailed surveys are used to assess local geologic or structural conditions.
A gravity survey consists of making gravity measurements at stations along a profile line or grid. Measurements are taken periodically at a base station (a stable noise-free reference location) to correct for instrument drift.
Gravity data contain anomalies that are made up of deep regional and shallow local effects. It is the shallow local effects that are of interest in m...
SCOPE
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, groundwater 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 D420, D5753, D6235, and D6429, and Practices D5088, and D5608.
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 sugg...
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Standards Content (Sample)
NOTICE: This standard has either been superseded and replaced by a new version or withdrawn.
Contact ASTM International (www.astm.org) for the latest information
Designation: D6430 − 99 (Reapproved 2010)
Standard Guide for
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Using the Gravity Method for Subsurface Investigation
This standard is issued under the fixed designation D6430; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision.Anumber in parentheses indicates the year of last reapproval.A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
1. Scope and space. A discussion of these other gravity methods,
including vertical gravity gradient measurements, is not in-
1.1 Purpose and Application:
cluded in this guide.
1.1.1 This guide summarizes the equipment, field
1.2.3 The approaches suggested in this guide for the gravity
procedures, and interpretation methods for the assessment of
method are the most commonly used, widely accepted, and
subsurface conditions using the gravity method.
proven. However, other approaches or modifications to the
1.1.2 The gravity method described in this guide is appli-
gravity method that are technically sound may be substituted.
cabletoinvestigationofawiderangeofsubsurfaceconditions.
1.2.4 This guide offers an organized collection of informa-
1.1.3 Gravity measurements indicate variations in the
tion or a series of options and does not recommend a specific
earth’s gravitational field caused by lateral differences in the
course of action. This document cannot replace education,
densityofthesubsurfacesoilorrockorthepresenceofnatural
experience, and should be used in conjunction with profes-
voidsorman-madestructures.Bymeasuringspatialchangesin
sional judgment. Not all aspects of this guide may be appli-
the gravitational field, variations in subsurface conditions can
cable in all circumstances. This ASTM document is not
be determined.
intended to represent or replace the standard of care by which
1.1.4 Detailed gravity surveys (commonly called micro-
the adequacy of a given professional service must be judged,
gravity surveys) are used for near-surface geologic investiga-
nor should this document be applied without consideration of
tions and geotechnical, environmental, and archaeological
a project’s many unique aspects. The word “Standard” in the
studies. Geologic and geotechnical applications include loca-
title of this document means only that the document has been
tion of buried channels, bedrock structural features, voids, and
approved through the ASTM consensus process.
caves, and low-density zones in foundations. Environmental
1.3 Precautions:
applications include site characterization, groundwater studies,
1.3.1 It is the responsibility of the user of this guide to
landfill characterization, and location of underground storage
follow any precautions in the equipment manufacturer’s rec-
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tanks (1) .
ommendations and to establish appropriate health and safety
1.2 Limitations:
practices.
1.3.2 If this guide is used at sites with hazardous materials,
1.2.1 This guide provides an overview of the gravity
method. It does not address the details of the gravity theory, operations, or equipment, it is the responsibility of the user of
this guide to establish appropriate safety and health practices
field procedures, or interpretation of the data. Numerous
references are included for that purpose and are considered an and to determine the applicability of any regulations prior to
essential part of this guide. It is recommended that the user of use.
the gravity method be familiar with the references cited and 1.3.3 This guide does not purport to address all of the safety
with the Guides D420, D5753, D6235, and D6429, and concerns that may be associated with the use of the gravity
Practices D5088, and D5608. method. It is the responsibility of the user of this guide to
establish appropriate safety and health practices and to
1.2.2 This guide is limited to gravity measurements made
determine the applicability of regulations prior to use.
on land. The gravity method can be adapted for a number of
specialuses:onland,inaborehole,onwater,andfromaircraft
2. Referenced Documents
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2.1 ASTM Standards:
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D420GuidetoSiteCharacterizationforEngineeringDesign
ThisguideisunderthejurisdictionofASTMCommitteeD18onSoilandRock
and is the direct responsibility of Subcommittee D18.01 on Surface and Subsurface
Characterization.
Current edition approved May 1, 2010. Published September 2010. Originally
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approved in 1999. Last previous edition approved in 2005 as D6430–99(2005). For referenced ASTM standards, visit the ASTM website, www.astm.org, or
DOI: 10.1520/D6430-99R10. contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
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Theboldfacenumbersinparenthesesrefertothelistofreferencesattheendof Standards volume information, refer to the standard’s Document Summary page on
this standard. the ASTM websi
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