Abstract:
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Development of a large data‑center campus in central Virginia required the construction of ten welded‑wire MSE gabion retaining walls to manage major site grading transitions. Subsurface investigations showed that four of the ten walls were underlain by compressible soils where anticipated settlements exceeded project performance criteria. These settlement concerns made foundation improvement necessary to limit total and differential movements and to provide a predictable, uniform deformation platform for the reinforced soil structures.
Because the zones requiring settlement mitigation overlapped with areas where global stability factors of safety were marginal, the design team implemented a unified approach: aggregate pier ground improvement was used not only to control settlement but also to provide the additional foundation shear resistance required to satisfy global stability requirements. This avoided the need for multiple stabilization methods and allowed a single, continuous foundation improvement system to support the critical wall segments.
The increased stiffness and shear strength of the improved ground enabled several key design optimizations. With higher composite foundation strength and reduced anticipated deformation, the walls could be designed with shorter geogrid reinforcement lengths, reduced minimum embedment depths, and more efficient overall wall geometries. These refinements reduced excavation limits, simplified construction sequencing, and improved constructability without compromising wall performance. The integration of ground improvement and MSE wall design also reduced the sensitivity of the system to local variations in subsurface conditions along long wall alignments.
This presentation will discuss the engineering rationale for using ground improvement to address both settlement and stability, how improvement depth and spacing were tailored to wall height and loading demands, and how transitions between improved and unimproved foundation zones were handled to maintain structural compatibility. Construction considerations—including sequencing ground improvement with wall erection, verification of improvement performance, and field adjustments based on observed conditions—will also be addressed.
This case study demonstrates how strategic ground improvement, when integrated with a flexible gabion MSE wall system, can provide a single, comprehensive solution for settlement control and global stability, resulting in a more efficient and robust design for large, geotechnically challenging site development projects.