Mega Brace Shoring Provides Unique Solution For Water Project

By Jeff Griffin, Senior Editor | December 2010 Vol. 65 No. 12

Graham said that to install the bracing, Garney Construction first pre-drilled a series of 30-foot deep dewatering well points around the excavation site. In accordance with the engineer’s design, five feet of soil was excavated from the top and sloped back.

“One of the Mega Brace ring/levels was assembled with the hydraulic rams pulled in smaller than the finished pit size,” he continued. “This was used as a template for the sheet pile being driven. After all the sheeting had been driven to grade/point of refusal, Territory Unlimited crew members excavated the pit seven feet with the Mega Brace ring/level going down at the same time. At this point the Mega Brace hydraulic rams were pumped out one at a time in all four corners.”

Safety chains were then secured from the Mega Brace to the top of the sheet pile. Territory Unlimited excavated another seven feet and the four legs of the Mega Brace were lowered into the pit and pinned together and the four hydraulic rams pumped out to lock the system into place.

“Safety chains were attached again,” Graham continued. “We repeated the process with a double stacked ring/level of Mega Brace seven feet below the middle ring. At this point, Territory Unlimited completed the excavation to final grade.”

Timing
Three days were required to drive the sheet pile, and it took five days to install the four rings/levels of Mega Brace to the 25-foot depth. Excavation of the remaining five feet and completing the finish grade took another two days.

Soil conditions were sand and gravel. “The soil type made for a relatively simple installation,” said Graham. “The challenges of the project were the depth of the excavation and dewatering necessary because of the close proximity to the river.”

United Rentals provided two teams on this project to make sure things went as smoothly as possible.

Graham said Mega Brace system has been used in the United Kingdom and Europe for 30 years and was brought to the Unites States about five years ago.

“United Rentals Trench Safety Branches have been installing Mega Brace systems for five years,” Graham said. “This project would be considered moderately-sized compared to some of the projects United Rentals Trench Safety has done on the east coast. During the field and classroom training we did with Ground Force Engineering personnel from England, we saw projects with entire city blocks excavated 50 feet deep in London using the hydraulic Mega Brace and cross strut systems. Garney and Territory Unlimited are the first to use the system in Colorado. Both companies were great to work with.”