Design Optimization in Underground Coal Systems. Volume VIII. The Roof Truss: An Analysis with Applications to Mine Design. Final Technical Report

摘要

The purpose of this research effort was to optimize the application of the roof truss for use in supporting coal mine roofs. Model analysis using two-dimensinal, body-loaded, photoelastic models was supplemented with field data and testing. A detailed literature review was also undertaken. The detailed analysis of photoelastic models of roof trusses was pursued by varying a number of the truss parameters - center-span installation angles and blocking-point configuration. In obtaining reduced deflection, the best support was achieved employing an angle of installation of 90 exp 0 . However, due to roof failute considerations, the recommended angle of installation was 45 exp 0 . Blocking points were shown to have an effect on roof-support capacity as well as truss span, and field tests indicated that the installation of a roof truss actually raised the roof. Also, from field measurements, it was shown that all sections of the arch carried the same load. The use of the roof truss as a major support principle and device in underground coal mines was confined. The installation angle should be 45 exp 0 in any specified roof span. Blocking is an essential part of the arch installation and should be carefully implemented to insure maximum efficiency of the arch. It was concluded that: the truss installation of 45 exp 0 produces maximum benefit when the overall stability of the roof is considered; the two-dimensional, body-loaded photoelastic model may be used to analyze underground structures; in underground installations, all components of the roof truss structure sustain the same load; and uplift of the roof may be achieved during installation of the roof truss system. (ERA citation 06:013343)