HR: 0830h
AN: NG31A-0601    [PDF]
TI: Ground Penetrating Radar Technique to Locate Coal Mine Subsidence Features at Malakoff, Texas
AU: * Save, N
EM: nsave@geo.tamu.edu
AF: Texas A&M University, Department of Geology and Geophysics, Halbouty Geosciences Building, College Station, Tx 77843-3115 United States
AU: Everett, M E
EM: everett@geo.tamu.edu
AF: Texas A&M University, Department of Geology and Geophysics, Halbouty Geosciences Building, College Station, Tx 77843-3115 United States
AU: Brandt, J
EM: jon.brandt@rrc.state.tx.us
AF: Railroad Commission of Texas, Surface Mining and Reclamation Division, P.O. Box 12967, Austin, Tx 78711-2967 United States
AU: Reimer, W
EM: william.reimer@rrc.state.tx.us
AF: Railroad Commission of Texas, Surface Mining and Reclamation Division, P.O. Box 12967, Austin, Tx 78711-2967 United States
AB: Coal mine subsidence features around Malakoff, Texas, are being studied with ground penetrating radar (using a pulseEKKO system from Sensors \& Software Inc.). This work is being done in collaboration with the Railroad Commission of Texas (RRC). RRC has been carrying out reclamation of abandoned underground coal mines near this location since early 1990s. The history of the specific mining operations that took place in the 1920s and 1930s has been difficult to ascertain; therefore, the use of a geophysical techniques, like ground penetrating radar (GPR) to identify hidden voids and potential subsidence features, are vital to the reclamation process. The landscape at the field site in Malakoff is rolling with a moderate-relief, sandy mud substrate. Some of the mine workings have collapsed over time and, in some cases, have affected the surface structures by creating sinkholes. GPR data, employing 25 MHz and 100 MHz frequency, have been collected over a 3D grid pattern and azimuthal pattern in the vicinity of these sinkholes. The penetration depth of the radar signal was approximately 20 meters from the surface. GPR data represent the mine drifts/void spaces with hyperbolae that bound the top and bottom of the mine workings. Diffractions against possible boulders and variation in the stratigraphy are also seen. Post-processing of the acquired data, using software developed by Sensors \& Software Inc., provided a 3D representation of the voids and subsidence features. The goal of this research was to identify the efficacy of GPR in locating the subsidence features. Azimuthal surveys provide information regarding the connectivity between existing sinkholes. RRC ground-truthed the data during its reclamation process (in turn, the acquired geophysical data were used to guide the reclamation). Mine drift openings observed during ground-truthing from some of the sinkholes matched the orientation of the void space observed in the GPR data lines. The GPR data is helpful in understanding the utility of 25 MHz and 100 MHz GPR in locating underground void spaces at varying depths. This study also denotes the importance of understanding the effect of varying physical properties of the stratigraphy, which could be misleading as radar signals representing a void space. GPR technique also enables in identifying the potential failure features and to quantify the safety hazard.
DE: 9810 New fields (not classifiable under other headings)
SC: Nonlinear Geophysics [NG]
MN: 2003 Fall Meeting