Trenches boxes

A permanent or portable structure designed to withstand a cave-in in excavations or trenches. These structures can be pre-manufactured or job-built in accordance with the Occupational Safety and Health Administration (OSHA) regulation 29 CFR 1926.652 (c) (3) or (c) (4). It may also be called trench boxes or trench shields. See also Trench Shield. 

An engineered metal box that is placed in an excavation for the protection of workers. It does not provide structural strength to the excavation, but provides workers a safe worksite that protects them from collapsing material of the trench. A registered professional engineer must design the trench shield or trench box system, which can be pre-manufactured or built on site as necessary. 

To prevent cave-ins, excavations can be shored using timber or other materials. Sides can be sloped to reduce the overburden (weight and pressure exerted by large amounts of soil on the sides). Also, manufactured shield or trench box systems, or those designed by qualified engineers, can be use to protect construction workers. 

Contractors may also use a trench box or shield that is either designed or approved, or is based on tabulated data prepared or approved by a RPE. Timber, almninum, or other suitable materials may also be used. OSHA standards permit the use of a trench shield as long as the protection provided is equal to or greater than the protection that would be provided by the appropriate shoring system. 

If we do need to put in a trench box, we re going to have to make sure we can get a crane or other piece of equipment in there to install the box. It s tight quarters over there. Plus, we need to make sure the weight of the equipment combined with the saturated ground doesn t cave in the excavation. ... 

Knew that a trench box would provide the proper protection for employees working in the excavation. 

Shield (Shield system) means a structure that is able to withstand the forces imposed on it by a cave-in and thereby protect employees within the structure. Shields can be permanent structures or can be designed to be portable and moved along as work progresses. Additionally, shields can be either premanufactured or job-built in accordance with 1926.652(c) (3) or (c)(4). Shields used In trenches are usually referred to as trench boxes or trench shields. ... 

Trench box or shield—These do not prevent cave-ins but protect the workers who are in them if a cave-in happens. 

Soil testing must be done on freshly excavated samples from the work site the testing determines the soil type and type of soil protective system that should be used. The three basic protective systems are sloping and benching, shoring, and shield (trench boxes) (Figure 6-2). 

Distribution box Serves to distribute the flow from the septic tank evenly to the absorption field or seepage pits. It is important that each trench or pit receive an equal amount of flow. This prevents overloading of one part of the system. Dissolved solids Chemical substances either organic or inorganic that are dissolved in a waste stream and constitute the residue when a sample is evaporated to dryness. 

Trenches formed into the floor can provide a higher drainage flow rate than conventional floor drain boxes, resulting in minimal depth of the liquid runoff within the area served. Illustrations of drainage trenches are shown in Chapter 7, Figure 7-3. 

Fig. 13. Empirical relations between step height and thickness polished for various levels (PMD> ILDl, ILD2, and ILD3) and different features (lines 5 wide and a box of 2 x 20 fim ) for positions at the center and edge of each wafer. The so-called last spot feature in the ILD3 plot indicates a trench feature between two large boxes at the center of a wafer.

Renovation and Salvage. Similar to regulations outlined under "Trench Mortar Ammunition", with the exception that bouchons and firing mechanisms are not ten ova ted or salvaged unless directed by the proper authority Destruction. For offensive hand grenades and and rifle grenades, not more than 40 grenades shall be packed in close contact with each other in a box and the ensemble placed in a pit, about 4 ft deep, free from stones or other... 

An employee was installing a small-diameter pipe in a trench 3 feet wide, 12-15 feet deep, and 90 feet long. The trench was not shored or sloped, nor was there a box or shield to protect the employee. Further, there was evidence of a previous cave-in. The worker may not have been aware of that. The employee apparently entered the trench and a second cave-in occurred, burying him. He was found face down in the bottom of the trench. 

If it were expanded to the size of the planet, the surface of a glass-smooth billiard ball, for example, would have peaks higher than Mount Everest and valleys deeper than the Mariana Trench. Images from scanning probe microscopes demonstrate that no surface is perfectly flat, but that all surfaces are made up of bumps and holes, like a layer of golf balls in a box. 

A. Assuming that cave-in protection were required under 1926 Subpart P (Excavations), and that a shield were used to provide that protection, 1926.652(g)(1)(H) would require the shield to be ...installed in a safe manner to restrict lateral or other hazardous movement of the shield in the event of the application of sudden lateral loads. Therefore, although our standard does not set a maximum distance between a shield box and a trench face, an employer would be required to ensure that, in the event of a collapse of the face, the shield would not move laterally. Trench work is frequently performed with limited room for maneuver, which means that workers can be injured with just a little movement by a trench shield. 

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