Baltimore, MD: Augered Strain Relief Trench Construction, Dundalk Marine Terminal
Geo-Con was contracted to install approximately 433 linear feet of Augered Strain Relief Trench (SRT) at the 1800 Area of the Dundalk Marine Terminals in Baltimore, Maryland.
Chromium Ore Processed Residue (COPR) was used extensively as backfill for the Marine Terminals during their construction. During long-term exposure to water, the COPR exhibited significant expansion, resulting in problematic movement of the Marine Terminal soils and damage to utilities and surface structures. The five segments of SRT were intended to relieve lateral ground stress and provide strain relief by permitting lateral expansion of subsurface layers of COPR.
The SRT was installed as a series of overlapping two-foot diameter soil-mix columns. Columns were placed on 1.4-foot centers to provide the specified continuity and effective trench thickness. The in-place soils were mixed with horticultural-grade peat moss at a rate of 8-10% by weight of soil. The peat moss was slurried in a bentonite/water solution in Geo-Con's custom high speed/high shear batch plant and delivered through the mixing rig's wet-kelly system and mixed with the in-place soils using Geo-Con's custom made Shallow Soil Mixing (SSM) auger. The columns ranged from 10 to 15-feet in depth.
The SRT was part of an ongoing Pilot Study at the marine terminals. The project was completed within budget and with no health and safety related incidents. Geo-Con was also able to accelerate the SRT installation schedule and provide the client a valuable schedule gain.