DESCRIPTION

The project replaced two bridges built in the 1960s with three new bridges that separate local and freeway traffic.

CHALLENGES

Foundations soils below the MSE wall abutments for many of the bridges on the 11th Street Bridge project consist of 25 to 50 ft of low blow count organic silts and clays underlain by dense gravels. The original design for the project called for the use of wick drains and MSE wire wall surcharging which would result in 10 to 45 in. of settlement and take many months for settlement to be complete. The team did not have the extra time or additional detailing, labor and costs associated with two stage MSE walls.

SOLUTION

GeoStructures provided an alternative approach to the two stage wire-faced walls using GeoConcrete®Columns (GCC) support with piers that had capacities on the order of 350 kips and were placed on 7 to 9 ft centers. This allowed a single stage wall to be built which dramatically reduced the time frame for MSE wall installation and limited settlement to less than 3 in. GeoStructures also designed the MSE walls which helped to optimize the GCC and MSE wall designs for settlement and global stability. Statnamic testing was used to confirm the capacities of the 35 to 50 ft deep GCC elements supporting MSE walls up to 45 ft tall.