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3-D Full Wavefield Numerical Simulation Of Seismic Advanced Detection In Coal Roadway And Study Of Detection Method

Posted on:2012-11-20Degree:DoctorType:Dissertation
Country:ChinaCandidate:S T YangFull Text:PDF
GTID:1110330368988714Subject:Earth Exploration and Information Technology
Abstract/Summary:PDF Full Text Request
The coal roadway tunneling will be affected by various geological factors, such as faults, collapse columns and mined-out areas therefore must be advanced detection and prediction. Among many geophysical exploration methods, Seismic exploration has advantages of be sensitive to geological interface, high resolution and long detection range. Carry out coal roadway seismic advanced detection research has important realistic significance.3-D seismic full wave field was numerically modeled in various coal roadway models and a new detection method is presented in this dissertation. Full wave field characteristics were analyzed and propagation laws of all wave patterns in coal roadway were researched with three-component synthetic seismograms and snapshots. The main study results were showed as follows.Based on the 2-D implicit free boundary condition, the 3-D implicit free boundary condition in 3-D roadway models was presented. The software of 3-D full wave field seismic wave numerical simulation in roadway was designed and developed.The amplitudes of Rayleigh seam waves are higher than those of Love seam waves in coal seam the seismic wave field stimulated by a point explosive source. Motion track of particles caused by Rayleigh seam waves are approximate ellipses; however, the direction of ellipses axis are change with vibration time. Vertical component amplitudes of leaky waves of Rayleigh seam waves in surrounding rocks are higher than horizontal component amplitudes and higher than Love seam waves amplitudes in surrounding rock. The seismic waves in surrounding rock near coal seam still propagate as seam waves. With the thinner coal seam, the main frequency of seam waves change higher, the dispersion of the seam waves changes stronger, and the velocities of seam waves change higher.In the seismic wave field stimulated by a point explosive source before roadway head, Diffraction Love seam waves and reflected Love seam waves are strong. But diffraction Rayleigh seam waves and reflected Rayleigh seam waves are weak. Strong roadway surface waves and weak roadway head diffraction waves propagate along roadway walls. However, weak roadway surface waves and some roadway head diffraction waves energy propagate along roadway floor.A new coal roadway seismic prediction strategy was presented by 3-D elastic finite-difference seismic wave modeling. Coal seam waves are stimulated by a point explosive source before the roadway head. Then reflected coal seam waves are reflected back when direct coal seam waves reach structural surface. Horizontal component of reflected Rayleigh seam wave and reflected Love seam waves are weak and interferences by roadway surface waves and roadway head diffraction waves around roadway. But vertical component of reflected Rayleigh seam waves has advantages of higher amplitude and less interference by the roadway surface waves and the roadway head. Therefore, vertical component of reflected Rayleigh seam waves which can be received in the roadway and floor is the marks of geological interface before roadway head.
Keywords/Search Tags:staggered-grid finite difference, seismic wave numerical simulation, roadway advanced detection, three-dimensional full-wave field, Rayleigh seam wave
PDF Full Text Request
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