Fiberglass Soil Nails proved to be the best solution for excavation

As part of the San Diegos Downtown Redevelopment District, Little Italy, San Diegos tiny but colorful Italian neighborhood, is going through its biggest upheaval in 40 years. Virtually every block is either under construction or about to be.

More than a dozen residential and commercial projects are under construction or in the planning stages in this historic Italian immigrant community that was home to workers employed in San Diegos once thriving tuna industry. In recent years, the area has been transformed into an urban neighborhood alive with a mix of single-family homes, condominiums, apartments, restaurants, art galleries and myriad of specialty shops.

Included in this community's renaissance is the Harbor Landing North & South Project, which will be a 200-unit apartment complex with 9,316 sq. ft. of retail space and 211 subterranean parking spaces. This new development that straddles both the north and south sides of Grape Street required temporary shoring for the soil excavations, which were necessary for the construction of the foundations and basement/parking. These excavations presented challenges due to the City of San Diegos restrictions on possible future subsurface interferences which had been dealt with in the past using removable sleeved DYWIDAG THREADBAR® Tie-backs, but due to waterproofing requirements of the structure in an area with a high water table, there was also a concern that the temporary holes in the waterproofing membrane to allow removal of the temporary tiebacks may compromise the integrity of the waterproofing.

In response, DYWIDAG Fiberglass Soil Nails were proposed, both to relieve the City’s concerns of burying steel elements under adjacent properties and roadways, which may present problematic obstructions for possible future excavations. This allowed the developer to obtain easements much easier and also to eliminate the need of blockouts for detensioning and removal of steel tiebacks, insuring an uninterrupted waterproofing membrane and continuous concrete wall surface, free of patches.

As part of the approval process, field demonstrations of DYWIDAG Fiberglass Soil Nails were conducted to demonstrate the ease of excavating through a buried fiberglass bar, which resulted in an approval by the City of San Diego.

This project, which began construction in July 2002 with a January 2004 targeted overall completion date, included approximately 400 each 20 foot long DYWIDAG Fiberglass Soil Nails installed in a 6 inch diameter grout filled shaft. The surface area of the shoring was approximately 15,000 square feet spread over two opposing excavations located across the street from each other and included underpinning excavation cut heights up to 25 feet. The fiberglass soil nails performed well and the shoring was completed without incident. Fiberglass bars are now the City of San Diego’s preferred soil nailing system.

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Sancor San Diego, CA, USA