Selecting Correct Shielding, Shoring

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

Trench shields and boxes consist of sidewalls separated by spreaders of various lengths to match trench widths. Shields provide a temporary protected opening in the trench for laying of pipe, providing a near vertical trench which is a very safe work space for in-trench workers.

Aluminum trench shields, boxes

Aluminum equipment serves the same function as steel shields but is made of lightweight aluminum and is designed for smaller excavations generally from rubber-tire backhoes and compact excavators. Included in this category are knock-down trench boxes of modular components consisting of two-foot high panels available in various lengths installed with corner posts. This option is effective for a wide range of excavations, including deep sewer and infrastructure projects.

Hydraulic shoring

Hydraulic trench shoring components are lightweight aluminum cylinders that shore or support the banks by utilizing hydraulic pressure arcs. This system is best suited for sites with smaller excavators as all components can be installed by hand.

Slide rail systems

Slide rail systems are made up of steel panels, which are similar to the sidewalls of a trench box, and vertical steel posts. T-Panels slide into the posts, creating a four-sided pit system. Using a “dig and push” method of installation, the panels and posts are pushed gradually into the pit as excavation progresses. Because a slide rail system is installed gradually, it prevents trench wall loss. With its ability to be used in a variety of arrangements, slide rail systems are considered by many to be the most versatile option available.
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Slide rails come in several variations: four-sided systems have one panel length on all sides tied together by corner posts. Linear systems have panels on two sides which are extended in a line to keep a long trench open. Panel lengths vary by requirements. Clear span systems have linear posts, corner posts and waler beams inside and outside the panels to provide a clear area without crossing members. This area can be up to 80-feet in any direction and 40-feet in depth. Four-sided multi-bay systems allow for a four-side excavation with one panel of width and unlimited length achieved by adding additional bays in the same way as a linear system.

Manhole shields

Manhole shields have short return walls on the open sides to allow narrow spreaders for pipe laying and wider spreaders at the manhole shield when required to set manholes – this keeps pipe laying as efficient as possible when a manhole is installed.