Investigations on longwall mining subsidence impacts on Pennsylvania highway alignments

Over 600 longwall panels have been mined in Pennsylvania in the last 50 years. Of those 600 panels, 25 panels undermined interstates highways. Despite this quantity of panels, much is still unknown regarded the detailed effects of undermining highways. The Gateway Mine, the Emerald Mine, and the Cumberland Mine undermined 1-79 with 17 panels in 1982-1989 and in 2003-2008, respectively; Mine 84 undermined 1-70 with 4 panels in 1987-2000. Through the examination of the panels that undermined 1-70 and 1-79, it is possible to determine which factors have most impacted the highway alignments. In some locations, the highway intersects with panels at angles ranging from 45 degrees to 80 degrees; and at the others, it runs between two panels, which simulates the effect of gateroads on the subsidence. The panel width to overburden ratio varies between 0.64 and 1.7, meaning that the interstates were influenced by both subcritical and supercritical subsidence basins. The face advance rates and overburden depths also vary between the panels. Unfortunately, specific information detailing highway impacts associated with unique characteristics of the subsidence basins are limited. In this paper, using the profile function model and influence function model within the surface deformation prediction system (SDPS), the effects of overburden, panel size, and orientation of the road on the highway can be indirectly assessed. (C) 2020 Published by Elsevier B.V. on behalf of China University of Mining & Technology.