Selecting Correct Shielding, Shoring

By Jeff Griffin, Senior Editor | April 2014, Vol. 69 No. 4

Underground utility construction today utilizes many “trenchless” construction and rehabilitation procedures that may greatly reduce the need to dig trenches or excavations to install and maintain buried infrastructure.

Even so, the bulk of utility work continues to be done by conventional cut-and-cover methods, and many trenchless procedures require launching pits where equipment is placed and receiving pits at the end of a trenchless segment. Much of today’s energy pipeline excavations require wide, deep, man-entry trenches.

Of course, earthwork is not limited to utility projects and preventing the collapse of walls of trenches and excavations has been a challenge since mankind first began digging holes in the ground.

Safety is the primary reason for shielding and shoring walls of excavations and government agencies enforcing standards applying to excavation safety. Trench shielding and shoring also is used to protect existing utilities from possible damage caused by nearby excavating.

Likely the first approach to preventing cave-ins is sloping trench walls, making collapse impossible. However, utility projects today are in locations where limited space does not permit sloping. Over the years, trench protective device options have evolved to meet changing construction needs.

Mike Ross, shoring specialist in the training section of shielding and shoring manufacturer Efficiency Production, said that “traditional methods such as timber shoring evolved from railroad and mining projects. The trench shield or box was a production tool developed in the Great Lakes region to combat the changing soil conditions created by glacial till. Lightweight hydraulic shoring was developed on the west coast and southwest where excavations were smaller due to shallower depths of pipe.”

Shoring product designs evolved to accommodate changing excavation needs and equipment. For example, smaller and lighter trench shields have become more prevalent since the expansion of the mini-excavator’s role in utility work.

“Today, different types of equipment are designed for different applications,” Ross continued. “All our equipment is matched to the excavation equipment used and task to be performed. Because of modular design, systems such as our Build-A-Box modular aluminum shielding system and slide rail shoring systems are most widely used across our distributor network.”

Challenges of underground utilities

Facilitating production and providing a safe work environment are primary goals of product designs, said Ross.