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The most widely used definition was developed in 1964 by D. U. Deere. It is the borehole core recovery percentage incorporating only pieces of solid core that are longer than 100 mm in length measured along the centerline of the core. In this respect pieces of core that are not hard and sound should not be counted though they are 100 mm in length.
The parameters to calculate the RMR value are similar to those used in the RMR system of Bieniawski. This may be confusing, as some of the parameters in the MRMR system are modified, such as the condition parameter that includes groundwater presence and pressure in the MRMR system whereas groundwater is a separate parameter in the RMR system of ...
construction parameters: size of tunnel; direction of drive; method of excavation. The RSR value of any tunnel section is obtained by summing the weighted numerical values determined for each parameter. The RSR concept is a very useful method for selecting steel rib support for rock tunnels.
Nowadays the classification system itself is not very often used, but the determination of the RQD as index for rock core quality is standard practice in any geotechnical rock drilling, and is used in many, more recent, rock mass classification systems, such as RMR and Q-system (see above). Rock Structure Rating (RSR)
TD – total depth (depth of the end of the well; also a verb, to reach the final depth, used as an acronym in this case [citation needed]) TDD – total depth (driller) TDC - Top Dead Center
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For example, the probability of core damage may increase while replacing a component, but the probability would be even higher if that component were to fail because it wasn't replaced. [4] Risk measures, such as core damage frequency and large early release frequency (LERF), determine the risk criteria for such changes.
where is the time average power loss per unit volume in mW per cubic centimeter, is frequency in kilohertz, and is the peak magnetic flux density; , , and , called the Steinmetz coefficients, are material parameters generally found empirically from the material's B-H hysteresis curve by curve fitting. In typical magnetic materials, the ...