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| Earth and Rock Works | Earth Retaining Structures | Geotechnical Hazards | Ground Improvement | Structural Foundations | Subsurface Investigation |
| FHWA > Engineering > Geotechnical > Geotechnical Hazards > Mines |
| Subject | From | Posted |
|---|---|---|
| Falling Weight Deflectometer (FWD) | Rick Ruegsegger | 02/12/2002 07:32AM |
| RE: Falling Weight Deflectometer (FWD) | Nick Priznar | 02/21/2002 08:00PM |
| RE: Falling Weight Deflectometer (FWD) | 02/28/2002 10:58AM | |
| RE: Falling Weight Deflectometer (FWD) | Thomas Lefchik | 11/14/2002 10:28AM |
| RE: Falling Weight Deflectometer (FWD) | Francis Drossaert | 02/10/2004 12:13PM |
| RE: Falling Weight Deflectometer (FWD) | Thomas Lefchik | 02/11/2004 08:40AM |
Messages posted for Falling Weight Deflectometer (FWD)
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Subject: Falling Weight Deflectometer (FWD) From: Rick Ruegsegger Date: 02/12/2002 | ||
| Last week, I spoke with Nick Priznar, ArizonaDOT, regarding the use of the FWD as a tool for locating subsurface voids beneath roadways. I explained to Nick that I had found that in some cases the FDW was effective for this purpose. It at least appears to sometimes be an effective "first strike" screening tool to define the limits of areas of roadway underlain by old mine workings. This,in itself, is valuable because it defines the boundaries for other types of subsequent testing or drilling. This fact is also important because OhioDOT owns FWD equipment which can be rolled out immediately in response to roadway subsidence events. I have actually had isolated peak DF1 and DF7 values which when drilled or excavated turned out to be mine tunnels. Has anyone had similar experiences? I have read technical papers describing TexasDOT use of the FWD to log top of bedrock at considerable depth. I spoke to John Duffy, Chairman of the TRB Committee on Highway Geology, about this subject. He said that if we as a new TRB subcommittee find a common interest in research on such uses of FWD, we could propose NCHRP research on the subject. Does anyone have any thoughts on any or all of my above ramblings? THANKS !
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Subject: RE: Falling Weight Deflectometer (FWD) From: Nick Priznar Date: 02/21/2002 | ||
| In regard to the FWD testing. It appears that I may have been pusing the limmits of the FWD testing. In a nutshell I was attempting to de termine if a DF1 value could be corrolated with a ground penetrating anomoly which may indicate a sub surface void. Geophysical testing resulted in hundreds of GPR anomloies on I-40 near the AZ Calfornia State line. AS most of the suspect sections were within 5 feet of the top of pavement I hoped that FWD data would determine which of these positions would be most suseptable to deteroation. The most suspetable sections were drilled but only a very small percentage demonstrated any void formation at all. However many sections of inconsestent to poor subgrade and several abandoned drainiage structures were identifed. The bottom line is although the techniqne didn't find a lot of voids, mabey there wasn't may to be found in the first place. Mabey this technique could be tested in an area of more pronounced problems to see if it has any benifit. Regards Nick Priznar |
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Subject: RE: Falling Weight Deflectometer (FWD) From: Date: 02/28/2002 | ||
| We in Maryland have FWD and we find it very useful for pavement evaluations. We have had success in mapping areas of saturated subgrades caused by utility ruptures. We have tried it in Karst areas to find signs of near surface voids. We are not convinced that it can locate viods at a comfortable depth. We have one area where we are looking at ridability data to see if long term settlement can be determined. We use resistivity surveys to guide our sinkhole (compaction) grouting operations. |
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Subject: RE: Falling Weight Deflectometer (FWD) From: Thomas Lefchik Date: 11/14/2002 | ||
| A literature search discovered that the Navy uses FWD to locate voids near drainage structures approximately 10' beneath airfield runways and taxiways. They look for anomolous readings and are confident that they are obtaining results down to the drainage structures. More research is needed to fully develop this method looking for and assessing deep subsurface voids. |
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Subject: RE: Falling Weight Deflectometer (FWD) From: Francis Drossaert Date: 02/10/2004 | ||
| I am currently writting an assessment of all possible techniques to detect mineshafts near railroads structures. Every known method will be reviewed, but I am not familair with FWD testing and certainly not in relation with void detection. Could anyone give some references of sciencetific papers that are dealing with FWD testing and void locating? Preferably in published in well-known journals. Thank you! |
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Subject: RE: Falling Weight Deflectometer (FWD) From: Thomas Lefchik Date: 02/11/2004 | ||
| Here are some related published studies. Determination of Depth to Bedrock from Falling Weight Deflectometer Test Data, Transportation Research Record No. 1504, 1995, pp. 68-78 Airfield Pavement Void Detection Technology, Naval facilities Engineering Service Center, Special Publication SP-2081-SHR, April 2000, http://www.nfesc.navy.mil/pub_news/voiddetection/V oidDetd.PDF Void Detection Under Airfield Pavements NAS Whidbey island and Nolf Coupeville, Naval facilities Engineering Service Center, Site Specific Report SSR-2617-SHR, April 2001 Effect of cavities on wave propogation: Formulation, by Jose M. roesset, Chine Chung Chieang, and Andre Campos Nogueira, published in Computer Methods and Advances in Geomechanics, ISBN 90 54 10 380 9, pp. 279-290 Effect of cavities on the propogation of surface waves, by Andre Campos Nogueira, Jose Manuel Roesset, and John Lambros Tassoulas, published in Computer Methods and Advances in Geomechanics, ISBN 90 54 10 380 9, pp. 949-954 Parametric examination of the falling weight deflectometer in void detection analysis, by David Allen Twiddy, a thesis/dissertation, University of Florida, 1983
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