Roane County, Tennessee

In early 2019, following a winter of heavy precipitation, Tennessee Department of Transportation (TDOT) personnel noticed cracks were occurring in an approximately 0.4-mile-long stretch of the westbound (WB) lanes of Interstate Highway 40 (I-40) along the south slope of Rockwood Mountain in Roane County, Tennessee. TDOT contracted with a geotechnical engineering consultant to perform a detailed geotechnical exploration and monitoring program. The consultant and TDOT developed a design (contract design) which would incorporate permanent tieback anchors with reaction blocks to stabilize the landslide. The contract design called for 1,714 (3-, 7- and 9-strand) anchors with each anchor bonded into bedrock below the slide surface. In the summer of 2020, TDOT awarded the construction contract for this project to Richard Goettle, Inc. Shortly thereafter, Goettle retained Burns Cooley Dennis, Inc. (BCD) to develop a Value Engineering (VE) design for the project.

The VE design used the same concept as the contract design, but used a smaller number of anchors than was called for in the contract design. The VE design reduced the number of anchors to 605 by using larger 12-strand anchors and longer bond lengths. The reduction in the number of permanent tieback anchors by greater than 275 percent was significant, allowing a greater spacing between the anchor and reducing the potential for the very long anchors to intersect. This reduction also minimized the overall project time for drilling through the boulder-strewn colluvium and residual soils to reach below the slide plane at depths reaching 200 ft. The on-site construction of stepped reaction blocks further improved construction efficiency and reduced construction-related traffic delays on I-40.

The VE design was accepted by TDOT in June 2021. Goettle achieved substantial project completion and installation of the tieback anchors in December 2022. The VE design significantly reduced the construction time, originally projected for the contract design in May 2024. The VE design provided slightly more load capacity than the contract design.

The project received special recognition for the following reasons:

• The design incorporated relatively large 12-strand anchors, allowing for fewer anchors to be needed to achieve the desired factor of safety;
• The required length of the anchors to reach stable bedrock below the shale surface and the boulders in the colluvial soils above the slide surface presented significant challenges;
• The flexibility of the VE design and construction techniques allowed for adjustments to be made quickly without significant impacts to the project schedule or cost; and
• The VE design allowed for the project to be completed 1.5 years prior to the originally projected completion date.

The stabilization of this section of I-40 is important to provide long-term stability to this important roadway in Tennessee. Because this stretch of I-40 crosses Rockwood Mountain, it is especially important, since closure of the interstate highway would require very time-consuming detours, affecting other portions of the Tennessee transportation infrastructure.

Pontotoc County, Mississippi

Burns Cooley Dennis, Inc. (BCD) provided geotechnical consulting services for bridge foundations and pavements and construction materials testing, inspection and engineering services for Mississippi Department of Transportation’s (MDOT) State Route 9 Design-Build Project in Pontotoc County, Mississippi.  The project consisted of approximately 9.5 miles of new four-lane roadway from U.S. 278/S.R. 6 near Pontotoc to U.S. 78 at Sherman. The project included eight at-grade intersections, an interchange at Endville Road and grade separations at Dozier Hill Road and Eads Creek Road.  Construction included 7 million cubic yards of earthwork, approximately 170,000 tons of asphalt pavement, and ten bridges.

Geotechnical services included preparation of geotechnical reports including pile design and verification using dynamic pile testing, drilled shaft design and verification using Osterberg load testing, stability analysis of embankment slopes and cut slopes, and settlement analyses of embankments.  Materials testing services included daily field and laboratory testing for embankment soils, design, soils, stabilized subgrade soils, cement stabilized subbase materials, granular base materials, shoulder materials, hot-mix asphalt pavements and concrete structures.  BCD also provided QC construction inspection services during deep foundation installation, bridge construction, embankment/roadway construction, hot-mix asphalt placement, pavement striping, and roadway signage and traffic control.

Marshall and DeSoto Counties, Mississippi

Burns Cooley Dennis, Inc. (BCD) provided construction materials engineering and testing services for the extensive SR 304 / I-269 project in Marshall and DeSoto Counties, Mississippi. These services included daily quality control (QC) field testing services for bridge construction and drilled shaft installation, and QC concrete compressive strength and aggregate testing.

Mason Road to Highway 178, Marshall County, MS (2012). This section of the project consisted of construction of four bridges along a new alignment crossing over Highway 178 and the BNSF railroad. Each of the four bridges was 1,500 linear feet in length. The bridge portion of the project consisted of 20,500 cubic yards of structural concrete, 5 million pounds of reinforcing steel, 60,000 linear feet of driven piling, 3,000 linear feet of 66-in. drill shafts and 38,500 linear feet of pre-stressed concrete girders. The project also included 700,000 cubic yards of embankment for the bridge headers and the realignment of Highway 178 for approximately 3,000 linear feet.

I-55 to Malone Road, DeSoto County, MS (2015). This section of the project consisted of grading, drainage and construction of eight new bridges. Grading for the project consisted of the removal of 1.5 million cubic yards of unclassified excavation, 844,000 cubic yards of borrow excavation, and 44,000 cubic yards of excess excavation. Drainage for the project was provided by construction of 7,000 linear feet of reinforced concrete pipe and 2,105 cubic yards of cast in-place box culvert. The eight new bridges required 9,800 cubic yards of bridge concrete, 62,850 linear feet of piling, 23,100 linear feet of precast pre-stressed concrete girders, and 2.1 million pounds of reinforcing steel.

These two sections of SR 304 / I-269, from I-55 to Malone Road and from Mason Road to Highway 178, will ultimately join with other state highway sections to complete the extensive and economically important I-69 corridor which will stretch from Canada to the Mexican border.