Ground Improvement on Strip-Mined Sites: Using Dynamic Compaction to Remediate Mine Spoil Sites

In what is becoming more and more common occurrence in the Eastern Coal Fields, a site that has been targeted for redevelopment is found to be covered with as much as 60 to 70 feet of uncontrolled mine spoil fills, placed at the conclusion of strip mining activities conducted during the past century. As such, they require deep foundations or a significant ground improvement effort to allow for shallow foundations to support vertical construction at the site. Today, many of these areas are being reused as part of infrastructure and site development associated with the shale gas industry. The use of dynamic compaction to improve mine spoils can provide an economic form of ground improvement, provided the magnitude of loading proposed at a site is reasonably moderate, and modest bearing pressures are required. Dynamic compaction has become an increasingly viable and attractive ground improvement option for mine spoil sites, given the ease of implementation and degree of effectiveness over a wide variety of ground conditions. Based on the 80 case studies reviewed as part of this study, dynamic compaction was found to be highly effective at improving sites with low-rise structures, and where measured, increased SPT N-values in the upper 30 feet of mine spoil materials up to 40% on average.