TDA As Lightweight, Sustainable Wall Backfill

When the design team for the Clover Ridge Apartments  in Chaska, Minnesota  needed an engineered lightweight fill to reduce the lateral load on the underground basement wall of this massive apartment complex, Braun Intertec recommended TDA (tire derived aggregate) engineered fill.   Backfill along the east wall of the west wing and south wall of the north wing of the building was specified to remove the pressure applied to the basement wall.

An estimated 3,000 compacted cubic yards of Tire-Derived Aggregate (TDA) ASTM D6270 – B was used. The TDA backfill was wrapped on all sides with a geotextile separator fabric to help prevent the migration of fine-grained materials into the TDA backfill zone. During placement, the TDA backfill is compacted under the weight of tracked equipment.

This project will host a four-story above grade apartment building with a footprint of 35,000 square feet with one level below grade for parking. Current grades range significantly from about 932 to 950, with the high point located on the east half and grades generally sloping downward to the north, west and south.

To help reduce lateral earth pressures applied to the basement wall, the active zone behind the wall must consist of the TDA material. To achieve this, the TDA should be placed within a zone extending up and away from the basement footings at an inclination of no less than 1H:1V (horizontal: vertical).

Using TDA as a lightweight aggregate and a reduced lateral load aggregate behind retaining walls and bridge abutments provided a touchpoint for future ongoing discussions about the use of TDA in engineering projects.

Proper engineering designs using sustainable TDA increases the safety factor of engineering projects, saves on the cost of materials, and adds an opportunity to contribute to a circular economy.

TDA reduces lateral loading by 50 percent compared to mineral soil, making it a superior backfill material. In addition, it weighs one-third of traditional soil.

© Scrap Tire News, June 2023