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Two types of conventional waveguides and mechanisms

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Two types of conventional waveguides and mechanisms of acoustic emission generated by the movement of soil mass: (a) solid; (b) hollow. Moving mass Materials of waveguide: steel, aluminum, stainless steel, others Slip surface Stable mass (a) Moving mass (b) Materials of filler: sand, rosin, fiberglass, others Slip surface Stable mass
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stage where fracture in the rock slope is macroscopic. To resolve this problem, a steel reinforcement bar was installed in the borehole along with acoustic emission transducers. During the final stage, acoustic emission directly related to fracture cannot reach the transducers but signals of large magnitude and those generated by friction between the reinforcement and surrounding cement based materials can be coupled to the transducers through the reinforcement. The reinforcement thus plays an important role in monitoring the macroscopic fracture through the waveguide. Although the acoustic emission waves may have nothing to do with the actual fracture mechanism of rock, acoustic emission counting and acoustic emission parameters could provide crucial information on the final failure. The waveguide has another advantage. Because the cement based filler material is mixed from known materials such as cement, sand and chemical admixtures, acoustic emission characteristics of the filler can be experimentally obtained by a series of fracture tests. Comparing field data with empirically obtained data, the fracture state of the rock can be readily evaluated in accordance with the flow. Fracture Criteria Because the waveguide consists of known materials, acoustic emission parameters giving fracture stages and types can be evaluated from several fracture experiments in the laboratory. Figure 19 shows the average acoustic emission energy with respect to applied load for a bending failure test (Fig. 19a) and a shear failure test (Fig. 19b) in reinforced concrete beams. The average in the chart is drawn by means of a moving average on the basis of data from 100 hits. In the bending test (Fig. 20a), the energy of acoustic emission is distributed around 50 counts in the primary fracture stage of bending. In the secondary fracture stage of bending, the energy appeared between 50 and 100 counts, followed by the value 319 Acoustic Emission Testing of Infrastructure F IGURE 18. Schematic behavior of the acoustic emission system during rock deformation: (a) intact state; (b) deformation with acoustic emission. Transducer Steel bar Macroscopic crack Cementitious materials (a) (b) Steel bar Transducer Acoustic emission generation F IGURE 19. Average energy as a function of load: (a) bending test; (b) shear test (see Table 3). 0.10 0.08 0.06 0.04 0.02 0.00 0 20 40 60 80 100 I b value of 100 data Load (percentage) Legend = 40 dB = 45 dB = 50 dB (a) 0.10 0.08 0.06 0.04 0.02 0.00 0 20 40 60 80 100 I b value of 100 data Load (percentage) (b)
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ranging from 100 to 200 counts in the tertiary stage of bending.
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  • Fall '19
  • The Land, Nondestructive testing, Acoustic Emission

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