3-D Geologic Modeling for Marine Trestle Foundation Design on Hampton Roads Bridge Tunnel Expansion Project Enhances Characterization, Visualization, and Communication of Subsurface Conditions.-PPT Presentation

PPT Presentation

Pdf Summary

The presentation describes 3-D geologic modeling for foundation design of the I-64 marine trestles over the James River in Virginia. The 2.7-mile bridge project connects Norfolk and Hampton, with north and south trestles linking the shoreline to expanded man-made islands. HDR and Mott MacDonald formed the design joint venture for the $3.8 billion design-build project awarded to HRCP Construction Joint Venture in 2019.<br /><br />Subsurface investigations combined historic VDOT data with supplemental marine exploration, totaling 225 SPT/CPT tests in the historic dataset and 229 SPTs plus 199 CPTs in the supplemental program. Exploration used jack-up barges in deep water and spud barges in shallow water.<br /><br />The area’s geology includes alluvial sand and clay, the Tabb Formation, and the deeper Yorktown Formation, which is particularly important for pile design and installation. Pile driving and CPT soundings can generate very high excess pore pressures.<br /><br />Three-dimensional modeling was used to visualize and organize soil data by geologic formation, including SPT and CPT resistance and normalized pore-pressure ratios. The models helped characterize variability in the Yorktown Formation, interpret potential pile-driving conditions and bearing behavior, and communicate subsurface conditions along the long bridge alignment. This variability also informed the question of how to define “site conditions” and determine the number of static load tests needed to apply the AASHTO resistance factor of 0.8.

Keywords

3D geologic modeling

foundation design

I-64 marine trestles

James River

subsurface investigation

SPT

CPT

Yorktown Formation

pile driving

AASHTO resistance factor