Evaluation of European empirical methods for subsidence in US coal fields
The purpose of this study was to assess the applicability of European subsidence methods for the emerging US longwall practice. Subsidence prediction in Europe has typically used either graphical methods (United Kingdom) or mathematical methods. The mathematical methods utilize either profile or influence functions. The graphical methods were developed in the United Kingdom (UK) by the National Coal Board (NCB) from subsidence data obtained from numerous mines. Although a large data base in the United States (US) is not available, the methods can be tested against some recent measurements of subsidence of an essentially flat deposit mined at a depth of 189 m in the Illinois Coal Basin. While the total predicted subsidence by the NCB method is approximately correct, the profile shapes are not well matched. On the other hand, the profile functions, which are fundamentally independent of orientation with respect to mining, give quite accurate representation of the measured profiles. Of the antisymmetric forms tried, a trigonometric form was slightly preferably because it predicted strains that were conservative, i.e., always somewhat greater than the measured values. These results suggest that much of the European subsidence experience is applicable to US practice. Consistent values of the parameters were found for profiles with similar initial conditions or similar orientations for two longwall panel results. It should be noted that the actual profiles were always somewhat more complex than the profile functions could adequately handle and that the development curves showed time-dependent effects as well. The magnitude of these time-dependent effects, while possibly small compared to the time-independent or instantaneous subsidence, are of importance and must eventually be incorporated into a proper analysis.
- Research Organization:
- Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Department of Energy, Carbondale, IL (USA). Carbondale Mining Technology Center
- DOE Contract Number:
- EY-76-C-04-0789
- OSTI ID:
- 5383438
- Report Number(s):
- SAND-80-0537
- Country of Publication:
- United States
- Language:
- English
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