Point of Beginning - April 2010 - (Page 32)

BIM Imaging technology makes fast work of creating caisson as-built models. a Box in BY DANIEL C. BROWN hen Kenaidan Con Contracting Ltd., of Mississauga, ntracting g Ontario, Canada, and its subcontractors were ask faced with the ta of expanding the local task fro om c water treatment plant from a capacity of 347 miln lion liters per day to 500 million liters per day, they a th knew the size of the area and the complexity of the structures would present a few challenges. The project involved building a walled-off excavation measuring plan roughly 50 by 55 meters in plan. The perimeter of the excavation was a polygon with 10 sides located near the existing water treatment plant. The depth of the excavation ranged from 5 meters to 21 meters. A subcontractor to Kenaidan drilled 1-meterdiameter caissons side by side around the excavation and filled them with concrete. In every second caisson, the subcontractor placed a steel H-pile. When the caissons were all placed, the subcontractor excavated the hole. As the excavation went down, anchors were drilled through the wall into the soil to tie back the secant wall formed by the big caissons. “The project was going 100 miles per hour, and we had this big hole with no access to the caisson walls to measure them,” says Dorin Nita, building information modeling (BIM) manager at Kenaidan. Kenaidan had figured on a tolerance of 7 centimeters on the secant wall. Interior concrete formwork and rebar had to fit tightly against the wall; any mistake in caisson placement would cause a problem. “We use 3D models on the job,” Nita says. “The challenge for us was to secure accurate and representative as-built information that covers the entire area in question.” W Getting the Real Picture Nita and his team considered their options and consulted with Greg Kettle, survey and GIS sales representative for Geoshack Canada. “At first, we thought we would scan the caisson walls using a reflectorless Above: The secant wall was composed of concrete caissons. Left: A 3D Autodesk Revit model of the structure that fits into the excavation. All illustrations courtesy of Kenaidan Contracting Ltd. 32 APRIL 2010 | Point of Beginning | www.pobonline.com http://www.pobonline.com

Table of Contents for the Digital Edition of Point of Beginning - April 2010

Point of Beginning - April 2010
Editor’s Points
A Grand Re-Entrance
Virtual Warfare
A Model Community
Tough Work in a Tight Spot
Show Me the Data
BIM in a Box
Traversing the Law
Professional Topography
Surveying GIS
GIAA Mailbag
New & Notable
Classified Ads
Ad Index

Point of Beginning - April 2010