In construction, shoring is the practice of bracing a structure using strong, temporary structures to avoid the collapse of materials or earth. An excavated trench is deep and narrow. The trench walls need to be stabilized with shoring materials in order to prevent accidents and protect workers. Shoring will also expedite the excavation process. However, it should be known that “shoring” is different from “shielding”. Shoring is propping up the structure to avoid the collapse of the earth, while “shielding” is the use of safety structures to protect workers in case of a collapse.
Below are some of different techniques utilized in trench shoring. Each technique is intended to safely stabilize the trench.
- Hydraulic Shoring: Hydraulic pistons are propped up until they push against the trench walls. Steel plates or plywood (either 1-1/8″ thick, or a the Finland Form {FINFORM} 7/8″ thick plywood) are used in collaboration with the pistons. This type of shoring expedites work and is the easiest method.
- Beam and Plate: The beams are planted firmly on the ground and reinforced with steel plates in between. Soldier boarding, which utilizes wood planks, also uses the same mechanism. This type of shoring is usually utilized for large excavations or for excavations that will span a long duration of time.
- Soil Nailing: Steel reinforcing bars and other strong, elongated bars are inserted into pre-drilled holes and sealed with a binding material (grout), or drilled and grouted at the same time in order to hold soil slopes, walls, or excavations. They are planted in a semi-downward incline, creating no tension. Sprayed concrete or lone soil nail heads are usually used as flexible or stiff facing.
- Continuous Flight Augering: Continuous Flight Augering (CFA) is the process of using concrete piles to support soil in an excavation site. A hole is created using a CFA drill, and pressure is used to introduce the concrete through the shaft when the auger is removed. No hole is retained, as a connected pile is being made.
Safe shoring practices are necessary to prevent trenching accidents. Standards are set by the OSHA to ensure that these proper practices are adhered to. OSHA standards are to be followed by all employees, with no exceptions. On any job site, there should be one person specifically responsible for implementing safety rules, but compliance with these rules is everyone’s responsibility. This person is known as the Competent Person. The Competent Person, by OSHA standards, is the worker who must check the trench site and adjacent sites for safety at least once a day. He or she is responsible for inspecting the site for a variety of factors that will determine the protective system to be used. Among the factors that the Competent Person must consider are:
- Soil classification – the Competent Person needs to identify correctly the type of soil to decide the kind of protection to utilize. Sometimes, more than one soil type can be encountered at a site.
- Other factors – water content in soil, the cut depth, changes in weather or climate, other operations occurring in the work site.
General safety rules should be implemented and followed, not only by the Competent Person, but by everyone on the job site. Each worker should be aware of his or her responsibilities at all times and should not be afraid to ask a supervisor or the Competent Person for clarification, if necessary. It is better to ask than to assume when in doubt.
Proper use of safety equipment should be emphasized at all times on any job site. Workers should always use proper eye and ear protection, as well as respirators, fall protection equipment, safety boots or shoes, and a hard hats as required by OSHA regulations. For excavations near road traffic, workers should wear bright vests so that they will be visible to passing cars. When shoring, always make sure that the trench walls are reinforced heavily and securely utilizing one of the above methods. In emergency situations, always follow OSHA regulations.
Shoring involves a certain degree of risk, but by following safety rules at all times, accidents can be prevented, and trench work can be completed safely and efficiently.