Solution

The GC worked with TVA’s consultants and Platipus engineers and sales team to develop an anchored solution to reduce the number of flowable fill lifts. It was determined that the clay soils below the pipe, together with the buoyant forces present during the backfill phases would require the Platipus B8 10 Ton Pipe Kits with a frequency of every 10’. The GC stated they were extremely pleased with their decision to use the Platipus pipe buoyancy control kits, as they were relatively easy to install using conventional equipment that was already on site, and they were able to eliminate several days from the backfill operation that would have required curing between lifts.

Solution

Based on an engineered required load of up to 11,000 lbs per location, Platipus offered both 2 ton and 10 ton capacity anchor solutions, depending on the required loads in a particular area. The soil was a dense, well-compacted sand which allowed for high loads to be achieved. Approximately 270 pipe anchoring kits, or 540 anchors, were supplied over a 3-mile long drainage line. The anchors were installed with a traditional jack hammer. Each anchor was loadlocked and the load was recorded in order to field verify that the design load was achieved on-site. The ability to field-verify loads, in addition to the small amount of equipment required to install, allowed the Platipus system to be selected in lieu of a combination of poured concrete footings and stainless steel strapping mechanisms.

Solution

The Engineer’s buoyancy calculations revealed the new pipe sections had a net uplift buoyancy force of ~370 lbs./ft. (7,425 lbs. per 20′ pipe section). It was determined that three Platipus S6C 2 ton pipe kits per 20′ section would provide 2,476 lbs. of force every 6′-8′, thus eliminating the buoyancy risk. The underlying bedrock mandated the use of cast iron Platipus S6 anchors driven to a depth of 5′. The convenience and ease of installation of the pipe kits using hand-held tools resulted in a cost-efficient solution with low environmental impact.

Solution

Based on an engineered required load of 12,000 lbs per location, Platipus offered a 10 ton ultimate capacity anchor system that was composed of S8 galvanized spheroidal graphite iron anchors and a combination of 8mm stainless steel wire cable and 50mm nylon webbing. The predominate soil types present on site were solid limerock at the surface and a dense sand layer beneath. Pilot holes had to be drilled through the limerock in order to drive the anchors to the required depth.

Sixty pipe anchoring kits, or 120 anchors, were installed in 3 days. The anchors were driven and loadlocked, the pipe was placed, and then the webbing and buckles were installed. This process was much faster than other competitive systems that involve forming and pouring concrete or filling and placing multiple sand bags over the pipes.

Solution

An analysis by the geotechnical engineer concluded that the sum of the weight of the soil and pipe was not sufficient to resist the potential vertical hydrostatic uplift force of the underground storage system due to the water table and limited amount of overburden. The structure required 834lbs/ft. to secure the underground system while meeting the required factor of safety of 1.5. The Platipus S8 anchor was selected after a review of the soils indicated a shallow water table and seasonal undrained soils. The contractor installed this solution at each bell end and evenly spaced at 4′ increments along the 20′ pipes.