The Manhole Box is a four-sided excavation protection system, which is used whilst installing pre-cast manholes, chambers or tanks. The manhole box can be used in conjunction with trench boxes. Manhole Boxes are made of high tensile steel, are heavier and are rated for deeper jobs. The square manhole configuration surrounds the pit and provides the needed inside clear span while reducing the amount of excavation and restoration required. For the rapid construction of manhole chambers and interceptors with each box being assembled and installed quickly and without the need for an operative to enter the unsupported excavation. Manhole Boxes are similar to trench boxes, however, integral end return panels provide additional support making them ideal for installing pre-cast manhole rings trench runs, without the need to alter the trench width.
A manhole shield has a typical base weight from 1100kgs, it is suitable for excavation depths up to 4.0m, Simple pinned strut arrangement, and a range of strut lengths is available for non- square configurations, 1.2m clearance under bottom strut, end closure panels available to support the open ends of the box. They can be used in trenches up to 5.5m deep in conjunction with up to two top extension units, they have five panel lengths which could suit all common pre-cast ring sizes, manhole boxes may be installed in either a pre-dug trench in stable ground, or by a progressive ‘dig and push’ method, handrail panels are available for manhole boxes; four-way handling points to aid safe assembly, maximum panel pressure must not be exceeded.
The Walls | Manhole Box
The manhole boxes come in both 3″ and 5″ walls. It is designed around the standard Utility box panel; there are 2′ composite return-wings added for extra coverage in a hole as opposed to a trench. Trench shields system involves the use of steel or aluminum trench boxes used for protecting utility workers while performing their duties within a trench. They are customarily constructed with sidewalls of varying thicknesses held apart by steel or aluminum spreaders. Spreaders can be interchanged to match the width of the trench. The different materials and building designs lead to a variety of depth ratings, i.e. the depth of a trench that the shield can withstand a collapse without buckling. Depth ratings are determined by registered professional engineers. The Manhole Box is always used when wider manholes have to be installed within a working trench. The trench shoring plate body is designed as a U-form and the wings have a thickness of 0.40m. Thus, a 0.80 m wide manhole is formed. Ahead and behind the manhole, normal trench shoring boxes ensure the trench safety. The spindles and accessories are identical to those of the trench shoring boxes.