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An Investigation of the Longwall Mining Subsidence Impacts on Pennsylvania Highway I-70: A Case Study

Adelsohn, Emily (2020) An Investigation of the Longwall Mining Subsidence Impacts on Pennsylvania Highway I-70: A Case Study. Master's Thesis, University of Pittsburgh. (Unpublished)

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Abstract

Over the last 50 years, longwall mining has become the most efficient and effective way to remove coal from underground deposits, like the Pittsburgh Coalbed. Longwall mining is a form of full extraction mining that allows large areas of coal to be removed. In Southwest Pennsylvania, longwall panels are typically approximately 15,000-feet long, 1,200-feet wide, and 7-feet thick. As these large areas of coal are removed, a subsidence basin is formed on the surface, causing the ground to drop several feet and inducing damaging horizontal strains and deformations. Although over 600 longwall panels have been mined in Pennsylvania’s Pittsburgh Coalbed, much is still unknown about how the formation of subsidence basins impact highway alignments and how these impacts can be mitigated.

In the winter of 2019, a 2,650-foot section of I-70 was undermined by a longwall panel in the Tunnel Ridge Mining district. This panel was monitored extensively by the Pennsylvania Department of Transportation, its contractors, and the University of Pittsburgh to provide a greater understanding of the impacts of subsidence on an interstate. Throughout the undermining process, surveys of the road and adjacent slopes were conducted regularly, and tiltmeters and inclinometers recorded data regarding the behavior of the deforming ground surface. The survey and instrumentation data were supplemented by weekly field observations made throughout the undermining process.

Extracting Tunnel Ridge Panel 15 caused as much as 5-feet of vertical subsidence and 1.5-feet of horizontal movement on the highway surface as the subsidence basin formed. These large movements caused measurable damage on the surface of the highway in the form of tensile cracks, open pavement joints, shear failures, and compression bumps. The reinforced concrete pavement structure and mitigation techniques, including full depth asphalt sections and contraction joints, caused the observations and survey data to deviate from the predictive models. The highway was additionally influenced by the presence of a large embankment which consolidated approximately 0.7-feet over 80-feet and spread laterally when undermined. As a result, this study determined that these factors have a significant impact on the behavior of a highway subjected to longwall mining subsidence and the mitigation thereof.


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Details

Item Type: University of Pittsburgh ETD
Status: Unpublished
Creators/Authors:
CreatorsEmailPitt UsernameORCID
Adelsohn, Emilyeda23@pitt.edueda230000-0002-5478-0984
ETD Committee:
TitleMemberEmail AddressPitt UsernameORCID
Committee ChairIannacchione, Anthonyati2@pitt.eduati2
Committee MemberVandenbossche, Juliejmv7@pitt.edujmv7
Committee MemberVallejo, Luisvallejo@pitt.eduvallejo
Date: 29 July 2020
Date Type: Publication
Defense Date: 6 March 2020
Approval Date: 29 July 2020
Submission Date: 20 March 2020
Access Restriction: 1 year -- Restrict access to University of Pittsburgh for a period of 1 year.
Number of Pages: 189
Institution: University of Pittsburgh
Schools and Programs: Swanson School of Engineering > Civil and Environmental Engineering
Degree: MS - Master of Science
Thesis Type: Master's Thesis
Refereed: Yes
Uncontrolled Keywords: Subsidence, Longwall Mining, coal, Highway damage
Date Deposited: 29 Jul 2020 15:52
Last Modified: 29 Jul 2020 15:52
URI: http://d-scholarship.pitt.edu/id/eprint/38353

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