Seismic Waves Distribution from Blasting in a Rock Massif with One Crack or System of Parallel Fissures (original) (raw)

Abstract

Explosive action of cylindrical charge was studied in an anisotropic rock massif which contain cracks or system of parallel fissures. Sound wave theory was used for qualitative pattern of seismic wave distribution around blasting. Results show changing of seismic waves from round to elliptical shape during distribution through rock massif with cracks. http://pubs.sciepub.com/ajcea/4/2/2/

Figures (3)

Figure 1. Seismic wave passing through fissure from blasting of vertical borehole charge 3 - charge; a -wave, which is down coming on fissure; 6 - reflected wave from nearest crack to charge; B - refracted waves from nearest crack to charge; r - reflected wave from the remotest charge to crack; 7 - wave that passes through the crack; 61, 62, 63 - angle of wave refraction, angle of wave reflection and angle of wave falling, correspondingly; 1, 2, 3 - medium behind a crack, a crack and the crack front, respectively.

Figure 1. Seismic wave passing through fissure from blasting of vertical borehole charge 3 - charge; a -wave, which is down coming on fissure; 6 - reflected wave from nearest crack to charge; B - refracted waves from nearest crack to charge; r - reflected wave from the remotest charge to crack; 7 - wave that passes through the crack; 61, 62, 63 - angle of wave refraction, angle of wave reflection and angle of wave falling, correspondingly; 1, 2, 3 - medium behind a crack, a crack and the crack front, respectively.

Figure 2. The scheme of seismic waves distribution in anisotropic medium with parallel fracture system Consider the case of the seismic waves falling at a distance R from the charge when the wavelength A is bigger more than the distance a between parallel cracks: dX >>a and R >>a (Figure 2).

Figure 2. The scheme of seismic waves distribution in anisotropic medium with parallel fracture system Consider the case of the seismic waves falling at a distance R from the charge when the wavelength A is bigger more than the distance a between parallel cracks: dX >>a and R >>a (Figure 2).

Figure 3. Seismic waves distribution in fractured massif around the explosion Equation (18) (23) (25) describe the distribution of seismic waves in the rock with cracks. Using these equations by the inverse problem of frequency analysis of incident and reflected waves can be solved, rocks structure and factor anisotropy can be determined. Distances to isoseismal line in the fractured massif around the explosion are defined by the formula (25) and obtained their distribution pattern is shown in Figure 3.

Figure 3. Seismic waves distribution in fractured massif around the explosion Equation (18) (23) (25) describe the distribution of seismic waves in the rock with cracks. Using these equations by the inverse problem of frequency analysis of incident and reflected waves can be solved, rocks structure and factor anisotropy can be determined. Distances to isoseismal line in the fractured massif around the explosion are defined by the formula (25) and obtained their distribution pattern is shown in Figure 3.

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