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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 |
|---|---|---|
| Early Warning System | Alan Miller | 10/28/2004 07:39AM |
| RE: Early Warning System | Kirk Beach | 10/28/2004 08:19AM |
| RE: Early Warning System | Bob Henthorne | 10/28/2004 08:43AM |
| RE: Early Warning System | Ken Rush | 10/28/2004 09:09AM |
| RE: Early Warning System | alan Miller | 10/28/2004 09:59AM |
| RE: Early Warning System | David Martin | 11/01/2004 08:59AM |
| Early Warning System | Leo Gilbride | 12/29/2004 08:01PM |
Messages posted for Early Warning System
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Subject: Early Warning System From: Alan Miller Date: 10/28/2004 | ||
| We are buiding roads across previously mined ground in the vicinity of Joplin, Missouri. We are investigating the worst areas, but are assuming some risk in other areas. I am wondering what methods we could use to automatically monitor for collapse and serve as an early warning system for closure of the road, even possibly hooked to a warning sign to alert the public until we can get our maintainance forces on site. I am thinking possibly vibrating wire buried longitudinally under the pavement. | ||
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Subject: RE: Early Warning System From: Kirk Beach Date: 10/28/2004 | ||
| Alan, Is this backfilled surface or underground mines? What is the depth? What is the composition of the overburden? Kirk | ||
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Subject: RE: Early Warning System From: Bob Henthorne Date: 10/28/2004 | ||
| Alan, We looked very hard at the this type of technology. We had planned to use TDR utilize an early warning system with call up. We had mainly talked to Kevin Oconner. | ||
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Subject: RE: Early Warning System From: Ken Rush Date: 10/28/2004 | ||
| Depending on the extent of the area to be monitored the IRIS suystem could be employed. Prisms mounted on structures and installed on borrus anchors can be monitored 24/7 by a unattended solar powered laser system with data posted on a web page and deformation criteria established to alert via web page and/or phone. This system can be somewhat costly but effective over large areas. | ||
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Subject: RE: Early Warning System From: alan Miller Date: 10/28/2004 | ||
| Kirk, This area is part of the tri-state lead and zinc mining area. Most of the deep mines are 160 to 180' deep room and pillar mines which mined planar deposits. We also have shallower mines where stopping occured. This area has been mined since the 1860's by anyone with a shovel. This is the job that Tim Newton did alot of geophysical work a few years ago. | ||
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Subject: RE: Early Warning System From: David Martin Date: 11/01/2004 | ||
| We are currently having a TDR system designed for some new roadways that cross active karst sinkhole areas. Bill Kane of Kane Geotech is doing the design. The project will be advertised for construction in spring 2005. | ||
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Subject: Early Warning System From: Leo Gilbride Date: 12/29/2004 | ||
| We (Agapito Associates, Inc. in Grand Junction, Colorado; www.agapito.com) recently designed and installed a subsidence early warning system in the Copperhill Mining District in Tennessee to monitor for potential crown pillar collapse above historical stopes. The top of the stopes were on the order of 350 ft deep. Vertical holes (5.5- inch-diameter) were drilled into the top of the stopes. One TDR cable and one single-point borehole extensometer was installed in each hole. The rationale for a combined instrument system is that the extensometers provide a first shot warning of initial movement and, thereafter, the TDR cable provides continuous monitoring of the position of the caving front. Propagation of the caving front to surface and subsequent subsidence is a process that often takes days or longer. TDR cables are generally less sensitive to movement than extensometers. Also, TDR systems must rely on data processing and typically require some interpretation to reliably diagnose ground movement, as opposed to extensometers which measure movement mechanically. Naturally, the redundancy of a combined system is also a major consideration. Rapid real time warning was needed in this case because heavy construction was planned over the stopes. Historically, large collapses have occurred in the area, one having consumed a dozer and operator. For these reasons, combined instantaneous warning followed by monitoring was deemed necessary. Movement on the extensometers was set to trigger a light and siren in the construction zone at surface. A solar-powered datalogger was used to record both the TDR and extensometer instruments. A telemetric relay of the datalogger data or warning signal to offsite personnel was considered, but not installed. This can be done and is a good option where public safety is involved. The Copperhill system has been in continuous use since March 2004 and, other than a lightening strike destroying one digital component in one hole, the system has performed reliably. The lightening damage was readily repaired. Site personnel regularly download the datalogger and provide it to our engineers to review. No subsurface movement has occurred to date. The monitoring system is expected to be in use for several more years, or possibly longer depending upon reclamation requirements. |
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