Charles H. Dowding
, Department of Civil Engineering
Northwestern
University
Prepared for Poster Session Presentation at 1997 Global Innovation Forum held in Washington, D.C., October 21, 1997, Sponsored by Civil Engineering Research Foundation
TDR is an electromagnetic technique originally developed to detect faults along power transmission lines. A pulser, connected at one end of a coaxial cable, sends a step voltage pulse along the cable line, and records the travel time of any voltage reflections resulting from cable discontinuities. Knowing the pulse propagation velocity, the travel time-reflection amplitude record can be converted to a distance-amplitude record. This technology has proven effective and is currently used in a number of projects to measure rock mass deformation along joint surfaces. Other existing and potential uses include measurement of soil moisture, contaminant migration, ground water level, piezometric pressure monitoring and leak detection. TDR measurement can be easily automated since the measurement is completely electronic. Thus, the approach lends itself to telemetry because of its inherently digital nature. Multiplexing further allows multiple cables to be monitored from the same pulser.
Coordination of Research with Commercialization
Differing aspects of TDR research have been supported by the US Bureau of Mines, the Infrastructure Technology Institute at Northwestern University (ITI), and the National Science Foundation (NSF). ITI focus has included specific steps toward commercialization in addition to the more fundamental research supported by USBM and NSF. ITI's participation in the commercialization process has highlighted ITI's assistance in development of new technology through 1) fostering cooperative demonstration projects with state Departments of Transportation, 2) attracting supplemental SBIR support and CPAR funds, and 3) providing enhanced channels for communication such as the Listserve News Group, WWW Clearinghouse, etc.
This article focuses on the issues related to commercialization of TDR technology rather than its technical details. Those details can be obtained at the TDR WWW Clearinghouse at http://iti.acns.nwu.edu/clear/tdr/. Topics addressed within the Research Summary include 1) Development of Critical Complementary Technologies, 2) Broadening the Market, 3) Development of Miniaturized, Low Power Pulser, 4) Symposium, TDR Listserve, WWW CLearing House & Book, 5) The Market, 6) Investment Opportunities.
ITI as a Commercializer
Aspects of this TDR research have been supported by the US Bureau of Mines, the Infrastructure Technology Institute at Northwestern University (ITI) and the National Science Foundation (NSF). ITI focus has included specific steps toward commercialization in addition to the more fundamental research supported by USBM and NSF.
ITI's participation in the commercialization process has highlighted that ITI can assist in the development of new technology through 1) fostering cooperative demonstration projects with state Departments of Transportation, 2) attracting supplemental SBIR support and CPAR funds, and 3) providing enhanced channels for communication such as the E-mail Listserve News Group, WWW Clearinghouse, etc.
Development of Critical Complimentary Technologies
Customer, clients, or owner/operators pay for service, not "boxes." And ultimately, provision of services requires both a company and a system of delivering from the "box." Since this CERF gathering is focusing upon technology, this discussion concentrates on the delivery system.
Detection of TDR cable shearing in soil required a lower priced pulser and an automated surveillance system to provide the necessary delivery system. While it is possible to cobble together an adequate delivery system as a research project in an experimental environment, it was not possible to easily deploy one that was field robust. Telemetry and remote acquisition of surveillance data is a general, infrastructure-wide challenge that is being addressed by others (ITI at NU among them). That general challenge is beyond the scope of this synopsis of TDR research. Furthermore, even if the telemetry/ acquistion challenge were solved, a miniaturized, low power consumption pulser would still be necessary.
Three significant challenges loomed over pulser development: 1) separation of pulser developers from the construction industry; 2) a defense-space orientation of key OEM's; and, most challenging of all, 3) a perception of a small market. Dispelling the small market perception seemed to have the most leverage to create enough interest in pulser development. In addition, its change would mitigate the impact, if not eliminate, the first two difficulties.
Broadening the Market
Broadening the market for TDR technology was felt critical for the generation of enthusiasm to develop the pulser. Interaction with OEM's, venture capitalists, and university administrators indicatd that markets of 100's to 1000's held no promise for investment, no matter how helpful the technology. Markets of 1000's to 10,000's attracted attention but little investment from OEM's. Supplementary funding in the form of SBIR's and the US Army Corps of Engineers CPAR program were necessary to attract OEM participation. Only at the 10,000 to 100,000 threshold was there interest on the part of all three.
To broaden the market for TDR technology, a series of steps have been taken with the support of ITI. The three most effective so far seem to be the develoment of the 1994 international TDR symposium, expanding and demonstrating the applications of TDR cable surveillance, and coalescing the application drivers through E-mail list servers and WWW information Clearinghouse.
Development of Miniaturized, Low Power Consuming TDR Pulser
After several years of negotiation, ITI was able to enlist HYPERLABS to construct a miniaturized pulser in conjunction with the US Army Corps of Engineers (USACE) Construction Productivity Advancement Research Program (CPAR). Such a device is critical to the success of other ITI-TDR activities as well as the NSF sponsored thrust in "cable- length" soil deformation monitoring. Since the USAEC was interested in TDR mainly for retrofitting Casagrande piezometers necessary for dam safety surveillance, the pulser was optimized for obtaining the strong air-water interface. However, as a by-product the pulser can also be deployed to obtain the smaller reflections from cable shearing necessary for deformation monitoring.
This pulser is sold with a sampler, memory, and data acquisition card built by Campbell Scientific (CSI). In fact, CSI builds both the pulser and the sampler. CSI feels that this instrument is not ready for sale at this time, and is producing only a limited number. Thus there still appears to be room for another instrument OEM to build its own field rugged pulser-sampler.
Symposium, TDR Listserve, WWW Clearinghouse, and Book
The 1994 symposium, sponsored by ITI and the US Bureau of Mines, brought together for the first time scientists and geotechnical engineeers to discuss the broad applicability of TDR pulsing technology. This symposium has been followed wiwth the ITI-sponsored E-mail TDR Listserve News Group and a WWW Clearinghouse that features full-text documents of TDR developments.
Critical documents in the symposium are available through the TDR Clearinghouse, whose address is http://iti.acns.nwu.edu/clear/tdr/. In addition, this WWW site supplies bibliographies, new publications, links to ITI related bridge research, TDR conference announcements, links to other TDR electronic resources, lists of TDR equipment vendors, lists of TDR researchers, etc.
The ITI-operated TDR listserve provides a pathway for
rapid communication in the TDR user's community. It can
be joined by sending the e-mail message: subscribe
TDR-L
The TDR book was written to legitimatize the market. A series of articles do not adequately convey an integrated view of the applications of such a broadly applicable technology as TDR. The articles emanate from divergent cultures with varying nomenclature and objectives. This variation tends to obscure the commonalities of the technology.
The Market
Despite fundamental differences in various types of TDR surveillance, all TDR instruments require a pulser. Thus development and popularization of any TDR technique will broaden the market for pulser develoment. TDR techniques provide two classes of data: "point-wise" and "cable- length". "Point-wise" deployment monitors only material near the end of the cable. "Cable-length" deployment allows monitoring of material response all along the cable.
"Cable-length" TDR development has been supported by ITI, the US Bureau of Mines, and NSF for applications in the monitoring of: 1) slope failure in either soil or rock, 2) subsidence from either abandoned mine collapse or sinkholes, and 3) pipeline protection against trespass or unwanted deformation.
"Point-wise" TDR development has been supported by the US Army Corps of Engineers, ITI, and the US Bureau of Mines for applications in 1) dam stability (piezometric pressure), 2) bridge pier stability (deformation), 3) contaminant detection, 4) petroleum leak detection, and 5) roadway stability (soil moisture).
Investment Opportunities
There remain several opportunities for investment in the 1000 to 10,000 installation market. The 100,000 installations in leak detection is already taken by Perm Alert. These opportunities are in development of speciality cables, improvement of the field stable pulse, and software, as well as in starting a company. Speciality cable opportunities are the most numerous. These opportunities exist for both cable-length and point- wise TDR configurations. Commercially available cables will have to be modified for TDR measurement of soil shearing (instability and subsidence monitoring), water level (dam safety), and contaminant detection, as well as additional configurations for soil moisture measurement.Despite a large step forward by the HYPERLABS pulser, there still seems to be a need to improve upon its performance. The two most pivotal needs for software are 1) automatic "at sensor" assessment and warning transmission, and 2) flexible cable-length signal acquisition.