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Dclormalion <br />49 mm <br />0 ~(Oplical Survey) I ' ~ <br />_ 55 mm <br />(Max. TDR) <br />30 - 32 mm <br />E <br />v <br />0 <br />5 \ <br />n 90~ ,_I~ <br /> <br />120 <br />FIG. 10. Comparison of Optically Surveyed Surlace Horizontal Displacelttent wills <br />Estimates of Cumulative Shear Dclormalion along Cable when Mine Face Is 3 m <br />away Irom Cable <br />TABLE i. Minimum and Maximum Estimates of Cumulative Shear De/ormation <br />along Cable when Mine Face Is 3 m away Irom Cable <br /> <br />7 <br />Gablo Allcr Dclormalion <br /> Rcllocuon Minimum Maximum <br />UcVlh coclhclmtl dclonnauon dclannalion <br />(m) (ntp) (min) (mm) <br />(U (2) 131 (4) <br />4x %.~~a 1.% 5.7 <br />M1o G5.1n 15.% 2V G <br />91 12.%11 4.h 7 1 <br />115 111,%% 4.2 6.$ <br />14% 111.24 .LI G.} <br /> ISum = 12.5 moll Ilium = 55.4 nun <br />Ihcr substantiates the ability to measure rcl:divc shearing dcformalion with <br />TDK signal elt:utges. A number of fac»tts, such :IS the exact cffccl of cable <br />diameter, cable Icnglh, number of crimps, and aanbinaliun of shearing and <br />extension, rcntain to be invcslig;ucd la intprnvc the resululion of the cur- <br />rcla»un bchvccu shear and rcllcclion. I luwcvc r, ingmrvcutcnts in resululion <br />arc not neccssar}• kt allow This system to be employed in the inytorlanl lack <br />u( early detection of shear delurm:d ion and ns inrrr.lse, which Ieuls to <br />Ltilurc. <br />"I'hcxc field nlcasurcntcnls verify the use ul TDR as :m c:uiy tea ruing <br />.ryslcm In dclccl sub%idcncc before iI ueeuls nn the surface. Cump:u isun of <br />'I'UR sign;nure eh;mgcs with surface subsidence ;a illuslrllcd in Pig. 6 shows <br />Thal lucalixul dsmges were detected when mining was G4 m (210 ft) away. <br />Nu surface nutventent was measured at Thal lime. <br />CONCLUSIONS AND RECOMMENDATIONS <br />Resuhs o(rcal lime, remotely controlled lime domain refleclomclry (TDR) <br />monitoring of cable deformation over an active lougwall coal-mining op- <br />cralion have been presented. Installation and dcvclopmcnl of the necessary <br />inxlnuncnls wcrc described, and the results of 'I'UIL mcasurcntcuts wcrc <br />contparcd with surface movements and overburden geology. Special attcn- <br />lion was devoted to the effects, as measured in the laboratory, of cable <br />Icnglh, c;lblc Ji:uncler, and shear-zuue width. Itascd upon Ihesc ntcasuro <br />mm~ls and obscrv:dions, tltc following conclusions :utd rccamntcndalions <br />arc ntadc: <br />Daily ur even hourly polling is esscmial fur the ntcasurcmcnl of <br />rock-mass dcformalion to obtain a complete history of cable dcfor- <br />malion prior to failure. <br />Remote control of TDR measurement via modem over existing <br />phone lines with serial communication nwdules is available but re- <br />yuires appropriate software to acyuirc and analyze the high density <br />of data aeyuircd over lime. <br />Rcnurlc pulling on den»nxl now allows cullccliun of TDR data al <br />sufficiently sm;dl lime intervals to dclccl early, deep-scaled rock <br />shearing that prcmdes surface movement. <br />Accunudalcd tcl:d ivc shearing along the cable, :Ili inlcrp rclcd from <br />TDIL signature chaugcs, compares favorably with weasured wrface <br />displ:tccmcnl. <br />Cable Icnglh has a signific:ml bW yuamifiablc cffccl on TDR rc- <br />fI000011%. <br />More I:Ibura Jury invesligaliuus of the cffccl of Icnglh, diameter, <br />dcformalion type, and cumber of crimps arc necessary to improve <br />the resululion of the rcOccliutt correlation with shear dcformalion. <br />ACKNOWLEDGMENTS <br />This research was funded by the Uurcau of Mines o(Ihc U.S. Department <br />of the Interior, mn(rncl number P02124G9. field installation and geo- <br />physical logging arc being conduclerl under the direction of Dr. Kevin M. <br />O'Connor, Civil Cnginccr in Utc Twin Cilics Research Ccnlcr. <br />APPENDIX I. INSTRUMENTATION <br />Inslnuncntation was designed to remotely monitor the dcvclopmcnl of <br />roo(cavingand the successive dcformalion of the ovcrlyingslrala in response <br />Iu lungwall mining. A 22.2 nu» (7/H in.) diameter (Wiring 1991) coaxial <br />cable was grouted into the Ills) rlrlltc lllallOlt borehole. Subseyuenl shear <br />defunnalion of the ruck mass deformed the cable, which created the re- <br />flecled'1'DK signatures Thal wcrc monitored with a "1'eklamix ISU211 cable <br />Tesler. 'f he cable lesser was controlled via nuulem communication over <br />public phone lines. <br />Thc'I'DR installation was one amtponenl o(a subsidence research project <br />antducled by the U.S. Uurcau of Mines in cooperation with the University <br />1422 <br />1423 <br />