2006 Issue

www.utahengineerscouncil.org 29 UECJOURNAL February 2006 STRUCTURAL ENGINEERS ASSOCIATION OF UTAH SOCIETY FORUM Staker Parson Company’s Beck Street gravel operation planned to install a high capacity gyratory rock crusher. The crusher and supporting frame is 50 feet tall to accommodate all of the appurte- nances for the crusher. This required that a 50-foot retaining wall be constructed adjacent to the frame to allow the haul trucks to dump the shot into the jaw of the crusher. In order to effectively achieve the 50-foot earth retainage, a mechani- cally stabilized earth (MSE) wall was cho- sen by the designers. The MSE wall design took advantage of the open pit configuration (no excava- tion required) and the generous supply of quality rock backfill material on-site. The project also required the use of a cast-in- place concrete wall in lieu of pre-cast pan- els or concrete blocks and their accompa- nying joints. To accommodate the close alignment of the crusher, the wall had to be placed vertical within an inch of the crusher frame and no batter was allowed. The key components of the wall con- sist of crushed rock stabilized with a syn- thetic geo-grid fabric, and a cast-in-place concrete fascia wall anchored laterally back into the MSE with steel rods and an- chor plates. The parameters for the retaining wall design were as follows: • Dimensions: 50 feet tall, 100 feet wide with twin 50-foot wing-walls (45°) • Loading: In-situ backfill pressures resulting in over 75 klf plus a 2000 psf surcharge at the top of the wall under the center truck loading apron. Geo-grid fabric from Huesker Inc. are manufactured from high-modulus, low- creep synthetic yarns and have a protec- tive polymer coating. This geo-grid pro- Gravel Pit Retaining Structure - North Salt Lake This duty to public safety is a responsibility that we as structural engineers do not take lightly. It is a very serious responsibility. By Phil Pack, Edited by Cameron Empey continued on following page ▲ The key components of the wall consist of crushed rock stabilized with a synthetic geo-grid fabric, and a cast-in-place concrete fascia wall anchored laterally back into the MSE with steel rods and anchor plates. STRUCTURAL ENGINEERS ASSOCIATION OF UTAH President Julie Ott ABS Consulting Vice President/President Elect Jeff Miller Reaveley Engineers & Associates Past President Barry Arnold ARW Engineers Treasurer Donald Barfus Tanner Smith Barfus & Associates Secretary/Historian Don Barker BHB Consulting UEC Delegate Jake Watson Calder Richards Consulting Engineers UEC Delegate-Elect Mike Buehner Reaveley Engineers & Associates Contact Information Julie Ott Phone: 801-634-6667 Email: seau@seau.org During Wall Construction – Behind the Wall