Figure 1 (above). Completed Turner Diagonal Intersection
Project Description
The Turner Diagonal Project was a joint venture between the Kansas Turnpike Authority (KTA), the Kansas Department of Transportation (KDOT) and the Unified Government of Wyandotte County and Kansas City, Kansas (US) to change the Interstate 70 and Turner Diagonal Parkway interchange to a diverging diamond interchange. The purpose of the project was to facilitate access to approximately 300 acres of land for potential economic development, reduce annual maintenance at the intersection and create more pedestrian access opportunities. In addition to converting the existing interchange, the project also included constructing new pavement in a truck staging facilities and a Kansas highway patrol vehicle inspection building to the west of the interchange. The new interchange required up to 30 feet of grade change and three mechanically-stabilized earth (MSE) walls, two of which were constructed above an existing box culvert that would remain in service during and after construction.
Challenges
- 10-month design and construction schedule from notice-to-proceed (NTP) to project completion
- Contract settlement criteria required observing less than ¼ inch over two consecutive, two-week periods prior to paving, delaying pavement by a month to confirm settlement criteria was met
- MSE wall design difficulties included:
- Soft foundation soils,
- Large differential settlements due to wall geometry and wall height changes over short distances,
- Influence of new embankments on the in-place existing culvert structure beneath two of the MSE walls, and
- Design flood elevation was above the bottom of the MSE wall.
Figure 2. Plans Showing the MSE Walls and Existing Culvert at the Turner Diagonal Intersection
Geotechnical Design Solutions
- Braun Intertec used borings, cone penetration tests (CPTs) and dilatometer tests (DMTs) to provide in-situ data and to evaluate the embankment settlement and slope stability while traditional laboratory testing was being completed.
- Braun Intertec designed a surcharge plan consisting of placing up to 8 feet of fill to increase the time rate of settlement and allow Clarkson Construction to pave approximately 90 days after fill was placed at the proposed ramps.
- The settlement monitoring and instrumentation program included utilizing shape arrays to monitor the soil settlement in real time, allowing the project team to evaluate if modifications to the surcharge plan was required to meet the project schedule.
- Collaborating with the design team, rammed aggregate piers were constructed below the MSE walls and 1 to 2 ½ feet of cellular concrete was used above the existing culvert. As a result:
- No surcharge was required
- MSE wall reinforcement lengths were shorter
- Lightweight fill volume over the culvert was reduced, and
- Global stability was met for the design flood condition
Figure 3. Installation of the Shape Array Below the Embankment
Project Completion
Due to effective design team communication and the ability to adapt, Braun Intertec supported the design-build team in the completion of a new diverging diamond interchange at the intersection of Turner Diagonal and I-70. The new Turner Diagonal interchange opened to traffic in September 2020.
