Interstate 10 was widened from four to six lanes and the twin bridges carrying I-10 over SR-281 were replaced with a single new bridge structure. Minor horizontal geometric revisions to the future six-lane section of SR-281 beneath the I-10 overpass were incorporated in the design to accommodate center piers for the new bridge structure. A revised typical section package and an updated border-width design variation were submitted and approved.
The new bridge structure over SR-281 is a 159.5-foot long double-span bridge supported by FIB 36 precast, pre-stressed concrete beams, and end bents constructed on Mechanically Stabilized Earth (MSE) walls. The bridge was designed and constructed to accommodate the future six-lane typical section of SR-281. Drainage improvements and signal upgrades at the ramp terminal intersections were part of the construction as well.
The geotechnical design consisted of further evaluations of the existing subsurface soils utilizing DMT soundings in conjunction with the existing project soils data for roadway and embankment design. The resulting test data was utilized to determine where predicted total settlement would exceed the RFP design requirements. Remediation of these areas exceeding the specified RFP requirements required subsurface soil improvements.
Rigid inclusions were installed at depths ranging from 35 to 45 feet below predevelopment grades and spaced as close as four feet on-center to ensure settlement requirements were met. Special wall and bridge foundation designs were also incorporated to minimize the effects of the compressible clay substrata.
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