Instrument to Measure the Initial Deformation of Rock Around Underground Openings.
Beus-MJ; Phillips-EL; Waddell-GG
NTIS: PB 279 657 :40 pages
This Bureau of Mines report describes a tunnel stress relaxation gage (tsr) developed to measure initial radial displacement around full-sized underground openings. The tsr technique was shown to be a valid concept in previous field verification tests. Sensitivity has been improved by employing a titanium alloy cantilever in the transducer head, which also permits a deeper sensor location. Use of improved fabrication methods such as stainless steel bellows and sputtering techniques and use of an environmental chamber for testing greatly increased overall reliability. A miniature data acquisition system (das) was interfaced directly to the transducer for increased versatility and containment entirely within a borehole. The present tsr system is suitable for use around full- size underground excavations, particularly machine-bored openings. Field evaluation of the improved instrumentation verified the design goals.
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