Some understanding of ground vibration standards - how they were developed, what they say, how they are properly used and what their shortcomings and limitations might be in construction contexts - is important to evaluating the reliability of statements based on standards. Following is a relatively non-technical description of vibration standards generally, their important limitations, the standards most commonly used for construction and blasting vibration, the limits they set, how they may be properly applied and what their use might mean for someone whose home or property may have been damaged by construction vibration.
Vibration Standards is one chapter of the over 100 page Construction Vibration Damage Guide for Homeowners (CVDG) (see example pages at right), downloadable free in PDF format (http://vibrationdamage.com/download.htm), ad and navigation-free with extra content, from Vibrationdamage.com or viewable, in part, online as web pages. You can find online an overview of its content, an Executive Summary, a broader view in its CVDG Introduction section, an introduction to the field and terminology in the CVDG's Vibration 101 for those new to vibration science and effects, and a hyperlinked list of all the pages available online in its CVDG Pro and Homeowners Contents page. The CVDG Professional Edition has, as part of its content, much more extensive information on the meaning, interpretation and applicability of vibration standards. Other pages of the Construction Vibration Damage Guide for Homeowners expand on the subject of vibration monitoring, a discipline critical to the meaningful use of vibration standards.
Vibration Standard Criteria
The blasting seismograph vibration monitor (example photo at left) is the most commonly used tool for measuring vibration and determining compliance with ground vibration standards. It is used in both blasting and construction settings, in spite of some serious limitations in measuring construction vibration. The monitor translates its raw observations into a number of different measures of the speed of ground vibration. The one most accepted in the field as an indicator of damage potential is the peak particle velocity (PPV).12 This, as the name implies, is a measurement of maximum ground particle movement speed, specified in the U.S. in inches per second (in/sec) and in most of the rest of the world in millimeters per second (mm/sec). This quantity is measured in all three perpendicular directions ("axes") of the seismograph's "geophones", as the magnet-in-coil detecting devices within the silver-gray, cylindrical seismograph transducer head are called.
PPV is a "vector" quantity (i.e. it has both a value and an associated direction). The peak vector sum (PVS) is usually also quoted; it is simply the square root of the sum of the squares of the PPV values in all three vector directions measured by the seismograph. PVS is a "scalar" quantity, i.e. one with only a value, which is always larger than the individual PPV vector values. Scientific studies have shown that the PPV correlates best with damage potential of all the tested characterizations of ground movement (e.g. acceleration, displacement, or strain). Virtually all the ground vibration standards are quoted in PPV values, not PVS or other measures of movement, although the "acceptable" values of PPV differ with the standard applied and with the frequency of the vibration components.
The three axes (directions) of measurement, the longitudinal (or "radial", the vector connecting the orientation arrow, as seen at right on the top of the seismograph transducer, and source of vibration), transverse (the vector in the same plane as, but perpendicular to, the longitudinal) and vertical (up and down) vectors, are always measured and reported separately. One reason for this is that they have different degrees of importance in causing damage. Structures are built to withstand vertical forces. For that reason, vibrations along the vertical vector are usually of lesser importance in causing damage, though not always benign.11 Vibrations in both the longitudinal and transverse vectors have the potential for causing shear in the home structure, which is a major contributor to damage effects. When in shear, various parts of the house move at different speeds or even in different directions, which can cause cosmetic cracking or even structural damage. Vibration standards generally do not take into account directly these differences in damage potential between vibration direction components, simply specifying the same limits for all three axes of measurement.
Vibration standards are set forth by governmental agencies or professional groups to provide guidance to those who might be expected to cause vibration in their work and want to avoid causing damage. There are different ground vibration standards for different vibration environments and different building types (see below). Thus, a judicious and reasoned choice of which standard to apply in a given situation is critical to proper use of, and benefit from, that standard.
Vibration standards are usually depicted graphically similarly to the U.S. Office of Surface Mining (OSM) blasting standard and USBM RI 8507 study plots at right,6,7 using log (logarithmic or non-linear) scales in both the horizontal and vertical directions. The vibration intensity (peak particle velocity in inches/second) is on the vertical scale and the vibration frequency is on the horizontal scale. Vibrations deemed "allowable" in these standards fall below the limits indicated by the central lines; "non-allowable" vibrations lie above the lines. Plotting the standards linearly (i.e. with equal intervals between units on the scales) will change the shape of the dividing line separating "allowable" from "non-allowable" vibrations dramatically, but will not change the standards themselves.
All scientific studies have limitations, including those of vibration damage and standards based on them. Understanding the limitations of scientific work is just as important in using that work as is understanding what the work says. Within their scientific limitations, such standards can be invaluable in helping to avoid unnecessary damage by telling contractors and others when their efforts should be of particular concern. They also suggest when and how vibration should be reduced to avoid damage.
Using Vibration Standards
Because not all vibrations felt by people are damaging to structures, vibration standards attempt to separate those vibration intensities and frequencies which are potentially damaging to structures from those which may be concerning to people, but pose relatively little damage probability. It is important to understand that standards are properly used to judge the probability of a single ground vibration of a given size (velocity), duration and frequency composition causing damage to a collection of houses or buildings of similar construction (see below), rather than the probability of multiple or long-lasting vibrations causing damage to one house or building.8 This differentiation is especially important in cases of construction vibration, where vibration is usually neither single nor short-lived.
One way of stating what the OSM and USBM RI 8507 standard diagrams above really mean scientifically is: "For a given single blasting-caused vibration, lasting less than a few seconds, with ground movement frequency components and velocities (intensities) which fall below the dividing line defining the standard, 95% of essentially intact houses on firm foundations, two stories or less in height, having the dimensions of typical residences, will not be damaged by that single vibration." That might be a mouthful, but that's what the standard and the data really say, at least within the confines of the USBM RI 8507 study which underlies both the standard plots above right. If any of the assumptions or conditions which underlie a ground vibration standard are not met in a given situation, then any use of that standard in that situation is potentially both unwarranted and misleading. Such improper use may also create an unnecessary risk to surrounding structures.
For the blasting settings which have been, by far, the most extensively studied, it has long been recognized that there is no given level of vibration which will or will not cause damage:
Acceptable vibration levels set in vibration standards are based on statistical analyses of damage probabilities, assuming "Gaussian", bell-shaped data probability distributions like the one shown at left.15 The statistical nature of standards means that not all vibrations which are deemed "allowable" (e.g. below the lines in the center of the standard compliance plots above6) in a given setting and standard will be non-damaging to all houses in all circumstances. Similarly, not all vibrations deemed "non-allowable" (those above the central lines at right above) will always cause visible damage. The relationship between vibration velocity (intensity) and damage probability is discussed in more detail in the CVDG's Vibration and Damage section. How standards can be used to set "safe distances" and provide other measures of damage risk can be found discussed in the CVDG's Vibration and Distance chapter and in the CVDG Pro's Vibration Safety section.
Thus, the mere fact that a given vibration is of an intensity within the "allowable" regime, even in an appropriately chosen and applied standard, cannot be taken as proof that a vibration of an "allowable" PPV did not or will not cause damage. It is scientifically inaccurate, inappropriate and misleading to say that it is "impossible" for a vibration of a given peak velocity (size) to cause damage to homes, even if it is within a given standard. If damage occurs from a vibration known to be within the "allowable" regime of a standard, that fact does not imply, by itself, anything about the construction, condition or design of the house(s) damaged. It could reflect an expression of statistical variation, differences between vibration intensities measured at the site of the seismograph and those at the house, local soil or geology conditions, differences in the frequency composition of the vibration, use of an inappropriate vibration standard, or vibration conditions which violate the assumptions behind the standard (e.g. vibrations lasting longer than "a few seconds"), among several other alternative explanations.
Our CVDG Pro chapter, Statistics and Vibration Damage, provides more insight into the role of statistics in setting vibration standards and the proper interpretation of the standards as reflective of probabilities, not certainties. Such statistical limitations don't imply that standards are without meaning, but they require that vibration standards be adopted, applied and interpreted thoughtfully and appropriately.
Frequency-Dependent Damage Potential
As described in the CVDG chapters, Vibration 101 and Vibration Frequencies, ground vibrations are usually complex, made up of multiple overlapping and interacting frequency components. The frequency components of the vibrations are important determinants of the damage potential. It is well known and understood that structures have natural vibration frequencies, called "resonances", a little like those of a tuning fork. Such resonant vibrations in homes are more felt than heard, due to their low frequencies.
At the home's resonant frequency, any repeated or long-lasting vibrations (more than a "few seconds"), like those caused by construction, can add to one another to produce even larger vibrations in the house structure (a process referred to as "amplification") than those occurring in the ground. Thus, the vibration in the house grows, rather than dying away in a few seconds. Even minor components of a vibration which occur at or near the resonant frequency or frequencies are potentially dangerous to the home, if they continue sufficiently long (e.g. in construction settings). Such resonant phenomena also bring into play so-called "fatigue" (damage caused by repeated flexing) issues.
For this reason, most ground vibration standards take into account the frequency dependence of the vibration damage potential, setting more rigorous standards for lower frequency vibrations nearer the home resonance frequencies than at higher frequencies. The OSM and USBM RI 8507 blasting standards above both set lower ground velocity limits near home resonance frequencies than at higher frequencies, but these differences (a velocity factor difference of 2.67 between frequencies above 40 Hz and at 10 Hz) are smaller than the observed amplifications (a factor of up to 4 for corner vibrations in homes, up to a factor of 8 for mid-wall vibrations), even for short-lived blasting vibrations.9 This difference between the known amplification factors and the smaller velocity factor ratios raises the question whether the velocity frequency factors may be set too low in those standards, even for blasting vibrations.
It is important to note that vibration standards set limits for ground movement velocities, not for velocities of movement in the home. Because of the self-reinforcing nature of vibrations with frequency components near the resonant frequencies, home vibration velocities can be substantially higher than the ground vibration velocities. Long duration, low frequency vibrations associated with construction are much more worrisome from the standpoint of producing resonant amplification of vibrations in the home than the relatively infrequent, short duration, higher frequency ones caused by blasting. Even low velocity vibrations involving ground impacts or impact-like sources (e.g. tracked equipment movement) are particularly dangerous, due to their broad frequency distributions, which assure resonant interaction and amplification in the home. For more discussion of resonance and fatigue effects, see our page Resonance/Fatigue.
Blasting-Related Standards and Studies
By far the most commonly used blasting vibration standard in the U.S. is the U. S. Bureau of Mines, Office of Surface Mining (OSM) standard1, shown above. It was developed in the early 1980's to address shortcomings of earlier, less stringent standards suggested by OSM. The OSM standard is based largely on the highly respected blasting vibration study done by the U.S. Bureau of Mines, Report of Investigations 8507 (USBM RI 8507) and studies referenced therein. As with most other standards, the OSM explicitly recognizes a frequency dependence of damage potential, with lower frequencies known to be more prone to causing damage. Many state and Federal agencies use this standard for blasting-related vibrations; others (e.g. contractors, vibration monitoring firms) use it inappropriately for non-blasting construction vibration.
An example of a construction vibration "compliance plot" showing the OSM and USBM RI 8507 limits is just above. The data points indicate the velocity and frequency properties of various components of that vibration. The vibration depicted there caused additional witnessed and videotaped damage, specifically correlated to a videotaped ongoing construction operation, in a home already damaged by construction. All the vibration frequency/velocity points are well within the "allowable" regime under the central lines for this blasting standard, providing a real-life demonstration that blasting vibration limits are inappropriately applied to construction vibration.
Differences Between USBM RI 8507 Safe Blasting Levels and the OSM Standard
For frequencies below 40 Hz, two limits are defined in the USBM RI 8507 study, on which the OSM standard is based, one at 0.75 in/sec PPV for "Modern homes, Drywall interiors" and one at 0.5 in/sec PPV for "Older homes, plaster on wood lath". The OSM standard does not explicitly recognize the Safe Blasting Levels of 0.5 in/sec PPV suggested in USBM RI 8507 for "Older homes, plaster on wood lath construction for interior walls" at frequencies below 40 Hz.5 Instead, it adopts the USBM RI 8507 recommendation of 0.75 in/sec for "Modern homes, Drywall interior" at frequencies below 40 Hz. Thus, if you have plaster walls, the blasting recommendation in the USBM RI 8507 study is lower than the OSM standard.
One further comment is in order regarding the USBM RI 8507 recommendations with respect to the 0.5 in/sec limit for houses with plastered walls. Many construction vibration types have these sub-40 Hz, higher intensity components. Often, they are the dominant frequency components (see Resonance/Fatigue). This differentiation is important, since vibratory compactor vibrations in a road construction job often exceeded the RI 8507 0.5 in/sec blasting limit for plastered wall homes (see left for one of many examples16), as well as several or all of the Federal Transit Administration construction vibration standard limits (see below). A large majority of these vibrations for which FFT frequency data were available had their dominant components below 40 Hz in frequency, as well as the majority of the total vibration intensity as a whole at frequencies below 40 Hz. Unless a detailed interior pre-construction survey is done to rule out the presence of homes with plastered walls in the relevant area, the 0.5 in/sec limit should be the one applied, and then only for those parts of any construction jobs which involve blasting.
Misuse of Blasting Standards in Construction Settings
The OSM standard is based on studies of damage probabilities from single short-lived blasting vibration events, rather than the semi-continuous ones generated by road or other construction using heavy equipment. The USBM RI 8507 study, on which it is based, indicates that continuous vibrations might require a more stringent standard:
Despite these and other indications that blasting standards are inappropriate in settings with vibration lasting longer than a few seconds, the OSM standard is widely cited, even outside of blasting. It is also misused, despite the cautions to the contrary in the underlying scientific studies, by some governmental agencies, construction contractors and vibration monitoring firms for relatively long-lasting, non-blasting construction vibrations, perhaps because it sets very high limits on ground vibration velocities (intensities).
Because such differences in application are so important, one must make certain that the correct and most applicable standards are utilized in a given setting. Construction-based vibration standards must be used for construction vibrations involving heavy equipment and blasting-based vibration standards for blasting. Use of scientifically inappropriate vibration standards is one of the most common mistakes made when vibration standards are cited.
The Swiss Standards
Another set of ground vibration standards that is widely cited worldwide is the "Swiss standards" (SN 640 312a). There are actually three separate "Swiss standards": one for blasting, a more rigorous one for pile driving and a still more rigorous one for machines and traffic. The last of these is the one which is most applicable to road construction and use, as well as most other forms of construction.
As with many other standards, acceptable levels of vibration in each of these standards are frequency dependent, with less vibration tolerated at frequencies below 60 Hz (Hertz, cycles per second) and still less below 30 Hz. The Swiss standards are not commonly used, per se, in the U.S., although they are widely cited and influential in ground vibration discussions and research. The Swiss SN 640 312a compliance plot at right above shows the same vibration in the OSMRE/USBM RI 8507 compliance plot above, caused by repeatedly dropping a large chunk (about 1/2 ton) of concrete on the ground about 6 feet from the seismograph (see videotape frame at left). It can be seen that the vibration at the seismograph is above several building type limits of the Swiss standard and of the related U. S. Federal Transit Administration standard, discussed just below.
The most relevant U.S. standard in a situation where there are no, limited, inappropriate or inapplicable construction vibration standards in the relevant state or municipality is the Federal Transit Administration (FTA) standard. The Federal Transit Administration's Noise and Vibration Manual (shown at right) is one of the most widely cited sources for vibration standards for road construction and traffic in the U.S. It is well worth reading in detail, as it has a great deal of summary information on vibration, noise and other construction impacts, beyond the vibration standard itself. It defines a standard for vibration in transportation-related construction situations, which is quite different from, and considerably more restrictive than, the OSM blasting standard. At the risk of some over-simplification, the FTA standard can be characterized as using the four structural categories and limits defined in the Swiss machines and traffic standard (quoted from Chapter 12 of the FTA standard4, 13 below):
FTA Vibration Limits
A typical modern, wood-framed home with drywall ("sheetrock", "gypsumboard") interiors and essentially no prior damage would be considered a Class III building. A home significantly damaged by construction, or any historic home or structure14, should probably be considered as a Class IV structure. While this assignment of damaged homes to Class IV might be disputed by some, the damage from the well-documented concrete dropping incident described above provides support for such an assignment.
A comparison of these FTA vibration limits with the vibratory compactor vibration plot above shows that the vibration levels from the compaction operation exceeded one or more of the FTA standards over 100 times in just an 18 minute period in front of a single home. Most other homes in the area experienced many vibrations which exceeded the FTA standard. Over 600 vibrations with velocities in violation of the FTA standards were found in the partial data produced for the road reconstruction project which generated them.
The FTA standard differs from the Swiss one in that it applies the high frequency PPV limit in the Swiss standard at all frequencies. Thus, this standard is more lenient than the Swiss, particularly at the lowest frequencies of most concern for resonant interactions with the home. However, it is far more confining on construction vibration than the OSM blasting standard. An expanded and updated version of the FTA Noise and Vibration Manual was issued in 2012 (cover page shown at right).13 The 2006 standard is unchanged in that version. You can find links to download free copies of most of these standards on our More Information page.
Municipal, County, State and Federal Vibration Standards
Individual state and Federal government agencies have set various standards for acceptable vibration velocities in various settings. They tend to be derived from, or identical to, one or more of the basic standards discussed here. Since Federal and some state highway departments have been among the most active in considering construction vibration issues insofar as they impact road construction, one should survey his own state's DOT web site for information on construction vibration standards specific to road and other construction in that state, if any exist at all.3
Some municipalities also have vibration standards of their own, which may not be identical to the state standards. You should check on the Internet for vibration standards in your city by using search strings like "[name of city] vibration". Such standards are too often set on the basis of advice from "experts" who do most of their work for construction or mining companies. Predictably, those standards are often based on the scientifically inappropriate, and much more lenient, blasting vibration standards, rather than construction standards. One good way to know if a municipal or state construction vibration standard is based on the U.S. OSM standard for blasting is to look for quoted limits of 0.75 or 0.5 in/sec. If these numbers are quoted, there is a high likelihood that the standard is derived from the OSM or USBM blasting standards. If your city has such municipal standards based on blasting, their appropriateness in a construction setting involving activities other than blasting can be easily challenged from a scientific standpoint. A discussion about setting state or local vibration standards appropriate for a given locale and type of vibration source can be found in the CVDG chapter, Vibration Regulation.
Most developed countries have human-caused (i.e. excepting earthquakes) ground vibration standards for at least some circumstances. Many of them are derived from or related to, in some ways, the three discussed above. There are separate standards for:
just to name a few. In addition, there is an
Many of these standards have been updated or reestablished in the last few years, so one should always use the latest applicable version. In the U.S., acceptable peak particle velocities are quoted in inches per second (in/sec), while most other worldwide standards are quoted in metric ("SI" ("Systeme Internationale") or "MKS" ("Meter Kilogram Second")) units of millimeters per second (mm/sec). Divide a standard quoted in mm/sec by 25.4 to convert it to in/sec used in the U.S.
Some of the standards referenced above do not set specific limits on vibration PPV's, but focus on proper procedures for measuring and analyzing vibration data. Others deal with machinery vibrations in factory settings, as well as construction and blasting-caused ground vibration. Most compare human vibration perception with the, often different, vibration levels necessary to cause damage in structures. There are also some different, far more stringent, vibration standards for areas which house some types of sensitive scientific or medical equipment (e.g. laser tables, MRI machines, spectrometers of various types, electron microscopes, etc.).17
Just as the OSM standard does not follow all the recommendations of the USBM RI 8507 study on which it is based, vibration standards around the world do not always implement the suggested or lowest allowable levels of vibration found in all scientific studies. For this reason, there may well be studies in the literature which give different limits for a given vibration situation than those quoted in the standards. If your structure or vibration source is significantly different from those covered by the standards, you should search the vibration scientific literature for recommendations more appropriate to your situation.
Of the world vibration standards, the FTA, Swiss, OSM, German, British and ISO standards seem to be the most cited within the ground vibration literature. You can get PDF-format electronic copies of virtually all of them over the Internet, though you may have to pay for some of them. Links to download the FTA, USBM and OSM standards for free are present on our More Information page.
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