Excavating on a building site poses the same risks as any other work, and although-statistics show that out of the more than 46,000 accidents on building sites each year, excavations are not the major hazard, they can often be serious. Indeed, about 10% of these accidents result in fatalities.
The Construction (Design and Management) Regulations, the Construction (Health and Safety) Regulations, the Confined Spaces Regulations, and Work at Height Regulations
Under these two acts, statutory instruments were drafted. The Design and Management Regulations were designed with the intention of decreasing operative injuries in the process of construction. The Health, Safety and Welfare Regulations detailed rules for excavations, shafts, tunnels, demolitions, and work near water. Lastly, the Confined Spaces Regulations covered chambers, pits and trenches. All four regulations applied to building operations and engineering construction because the risks faced by employees in the two industries are similar; therefore it is desirable to have a unified code of practice.
The Health, Safety and Welfare Regulations 12 and 13 mandate the standards for the supply and use of adequate support to excavations. They must be installed by qualified or trained operators, or supervised and inspected by a competent person. Construction work involving excavation must be inspected every shift, with reports filed detailing each inspection.
All employees and contractors have a duty to ensure the safety of their own workers. If you, as an employee, discover any defects or unsafe conditions in your workplace, it is your responsibility to report the facts to your employer, foreman, or designated safety supervisor.
Deep excavation trench
Deep trenches are those that are over 3 meters in depth. They are usually required for the installation of equipment like cables or drains because you don't need a deep foundation often. The excavation shouldn't be opened too far in advance of any proposed work, and it should be backfilled as soon as practical after the completion of the project. These two precautions will lessen the risk of falls, flooding and damage to completed work as well as releasing timbering for reuse at the earliest possible date. Great care must be taken in areas where underground services are present: they should be uncovered with care, protected and supported as needed. The presence of services in an excavation area may restrict the use of mechanical plant to the point where its use becomes uneconomical. Hand trimming should be used for bottoming out a trench, side trimming, end trimming and for form the gradient just before pipe laying or cable laying.
When excavating, it's necessary to close board or sheet the foundation to protect from any potential rock falls. However, the main exception is a hard and stable rock subsoil. Whenever working on a project in a rock layer, be sure to examine its stability closely. Fissures or splits that slope towards the cut face could lead to crumbling or rock falls when exposed to the atmosphere for long periods of time. If this is the case, than it would be prudent to timber the faces of your project according to how extensive and systematic the fissures are.
In areas with hard or firm subsoils, it might be possible to excavate the site before putting in timbering. The method of support for excavation sides is similar to that used for shallow and medium-depth trenches, except for the use of bigger sections to resist the increased pressure caused by being in a more deep area.
Driving timber and steel runners, trench sheeting, or interlocking precast concrete piles ahead of your excavation can be necessary when the subsoil is either weak, waterlogged, or running sand. Driving to a depth exceeding the final excavation depth or by using the drive-and-dig system will accomplish this. Long runners and steel piles will require a driving frame, while tucking and pile framing methods allow shorter members to be driven. All these methods require that both ends of consecutive members be secured with a single strut.
Timbering refers to any form of temporary support for the sides of an excavation. Some common purposes include:
- prevent the walls of your excavation from caving in;
- To complete the task, keep the excavation open for the necessary time period.
The term "timber" is often used when the material itself is employed, but it can also refer to different materials that fulfill the same function.
