By L. Dresen and H. Rüter (Auth.)

The effective mining of tough coal in deep coal mines utilizing hugely mechanized longwall ideas calls for info at the geological constitution sooner than the working face. Even minor tectonic faults with throws of just a couple of metres suggest a loss in productiveness, as they current critical operating difficulties for underground mining apparatus. simply because funding expenses to put in a mechanized face are excessive, ''insurance'' within the type of spare ability through either computer shifts or spare faces is uneconomic. hence, to lessen mining bills it truly is necessary to delineate the geology sooner than mining. at the present time, the single powerful geophysical instrument to observe and to map minor faults in entrance of the coal cutter is in-seam seismics utilizing channel, or so known as seam waves. The thoughts are good confirmed and effectively utilized for greater than decades.

In-Seam Seismics covers the full diversity of basic and complicated issues in arithmetic, physics and knowledge processing of dispersive channel waves. the result of analogue and numerical modelling offer a radical realizing of transmission, mirrored image, recording and interpretation of seam waves and coal seam disturbances. hearth damp facts instrumentation, goal oriented underground layouts, processing and interpretation of actual facts impart the state of the art of in-seam seismics. chosen and well-rounded case histories whole the presentation of in-seam seismics. they could aid the mining engineer to make your mind up to plot and to use in-seam seismics in case of underground mining problems.

A transparent textual content, basically formulae that are valuable, many conscientiously designed figures, a longer record of references and a lucid index make it effortless for the reader to get conversant in seam waves or to advertise the means of in-seam seismics

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Extra info for Seismic Coal Exploration. In-Seam Seismics

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D) Time envelopes of the (band pass) frequency filtered section of Figure b (at center frequencies 125 Hz and 475 Hz), with adjusted amplitudes. e. that of the fundamental Love seam wave mode calculated for a simple seam model) is shown at several distances with normalized amplitudes. It exhibits different shapes at different receiver distances, and in general is stretched from one record to the next. Thus, at different distances the same phase is associated with different frequencies due to this 'stretching'.

However, the propagation velocity of the seam wave is frequency dependent which is referred to as dispersion. e. 4). /5). *» AWil Am )J. 2 g/cm3 ) at several distances, (c) Phase velocity (upper curve) and group velocity (lower curve) of the dispersive wave train in Figure b. (d) Time envelopes of the (band pass) frequency filtered section of Figure b (at center frequencies 125 Hz and 475 Hz), with adjusted amplitudes. e. that of the fundamental Love seam wave mode calculated for a simple seam model) is shown at several distances with normalized amplitudes.

4) qrn = ( c ; 2 - ß ; V 2 The function tan"1 is restricted to the interval [0, π/2]. η is the 'mode ordering number' with n = 0, 2, 4,... denoting the symmetrical modes and n = 1,3, 5,... denoting the antisymmetrical modes. The following notation is commonly used: n = 0 first mode, base mode or fundamental mode n = 1 second mode or first higher mode n = 2 third mode or first higher symmetrical mode etc. 2,... 275) and the base mode has zero cut-off frequency. This is a special property of the fundamental Love channel wave mode propagating in a symmetrical rock-coalrock sequence with plane interfaces with the consequence that this mode branch has no extension in the leaky mode range (C > ßr) (Franssens, Lagasse and Mason 1985) and thus cannot loose energy through traveling body waves radiated into the rock.

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