Hello GeoPrac.net readers! I am Robert Thompson, a geotechnical engineer (P.E.) living in Alabama and working all over the U.S. as a partner in Dan Brown and Associates. My first contribution to this site (besides this post!) is an article on a project that I started working on at my previous employer, TTL, Inc., but completed after I joined DBA. Randy has added the article to the downloads area.
Download Design and Construction of Support Infrastructure for a New Quarry in Lee County, Alabama by Robert Thompson, Sheryle G. Reeves and John W. Grabar
The project was the design and construction of a rail spur to service a new aggregate quarry in eastern Alabama. The challenges included designing soil cut and fill slopes as high as 60 feet, and transitioning the lead track from the railroad mainline to an at-grade crossing of state highway between the quarry and the railroad mainline. It was challenging since the mainline was on an embankment 10 to 12 feet in elevation higher than the highway elevation and there was not enough space between the two to construct a simple earth-slope embankment. 
The limited space, poor soil conditions, and existing surface drainage pipes through the railroad embankment and between the highway and the railroad mainline resulted in an interesting combination of a box culvert, soil nails, compaction grouting, and a mechanically stabilized earth (MSE) wall, all built within a narrow strip between the railroad embankment and the highway. Take a look at the article to see how we did it all.
I hope to find time to post more often. Sometimes I find it difficult to make time to post to the DBA blog/website of which I am webmaster.
Abstract
Florida Rock Industries, Inc. (FRI) began investigating the development of an aggregate quarry in Lee County in eastern Alabama in 2000. Planning for the site required locating storm water detention ponds, a processing plant, the plant rail trackage, truck scales and planned limits of the quarry pit without infringing on the required undisturbed property perimeter buffer areas. The quarry and processing facilities were designed to accommodate local aggregate sales by truck and railcar shipments of up to 90-railcar unit trains. The two major issues for the planned rail facilities were: 1) the site grading required to optimally fit the required trackage onto the available quarry site area; and 2) the required grade crossing of a state highway to connect the plant trackage to the CSX mainline. The selected two-track loop configuration for the plant trackage required cuts of up to 30 feet and fills of up to 60 feet. Because of the relatively confined site area and the nearby retention ponds, slopes as steep as 2.5:1 (H:V) were required for the greater fill sections to fit the trackage in the available footprint. The construction of the lead track required the use of soil nails to stabilize the existing rail bed, compaction grouting to stabilize the subgrade, and a heavy duty MSE wall system for the lead track transition embankment. The design team worked closely with FRI throughout the development, design and construction process. Open communication between the various design consultants was critical to developing a workable design that overcame the challenges at the site. FRI’s careful selection of qualified, experienced engineers, consultants, and contractors was the significant contribution to the success of the project.
Thanks, Randy! The reinforced zone of the wall was relatively close to the soil nail wall along part of the alignment. The primary reason for the soil nails was to provide temporary excavation support to be able to excavate enough area to provide the necessary reinforcement lengths. Since we considered them “temporary”, we did not (conservatively) take a reduction in the lateral earth pressures. The surcharge loads from the trains on the spur directly above the reinforced zone ultimately controlled the MSE wall design.