Overall project includes building nine miles of HOV lanes, expanding the existing HOV lanes at I-395, making operational improvements to the existing HOV lanes, adding new or improved access points as well as building nine new bridges and three bridge widening.
New bridge abutments were built on top of very low shear strength marine clays which are locally a concern since they are prone to landslides. To mitigate the instability and to provide adequate bearing for the abutments, Cement Treated Aggregate (CTA) was specified by VDOT. Challenges included working in a tight location adjacent to the highway as well as the special construction requirement for the use of CTA. All CTA materials had to be used within eight hours after delivery.
The CTA increased the shear strength and capacity of the Geopier® elements while providing a low permeable pier which would not be a conduit for moisture to penetrate the highly plastic marine clays. A total of 151, sixteen ft long, 36 in. diameter CTA Geopier® elements were installed to support a portion of I-395 HOT Lanes. Several segments in the corridor also required retaining walls between the HOT lanes and the I-95 mainline to accommodate elevation differences between the I-95 northbound and southbound lanes.