Trench Supports or Retaining Wall
For every deep excavation, it needs to be carefully assessed to decide whether trench supports or a retaining wall are required for that excavation.
To prevent the sides of the excavation from collapsing, shoring and bracing may need to be used. They are essential for deep or narrow trenches, where the risk of material collapse is higher and operatives could be inside the excavation.
The trench supports we use often consist of steel trench boxes, hydraulic or pneumatic shoring, sheet piles, bracing systems (struts) and trench jacks. There are other considerations that also need to be made when using trench supports which are detailed below.
Retaining walls are an alternative option to supporting excavations, with a variety of different types they are very versatile to different excavations. We construct a variety of types of retaining walls including:
- Gravity retaining walls
- Cantilever retaining walls
- Sheet pile retaining walls
- Anchored retaining walls
- Gabion retaining walls (Gabion baskets)
- Mechanically stabilised earth walls
Overall, we evaluate and plan every excavation to decide whether support systems are necessary and if so decide the most appropriate form of trench support or retaining wall.
Temporary Works Design
When constructing any temporary structures or systems that support construction activities that aren't part of a permanent structure, a Temporary Works Design is required.
Our site management team carefully plan temporary works ensuring utmost safety, stability and efficiency during the construction process.
Temporary works designs have a variety of applications including:
- Scaffolding, working at a height
- Formwork, concreting
- Shoring, prevents collapse of an excavation
- Falsework, temporary structures to support permanent structures
- Temporary bridges or access roads, facilitate deliveries of materials and movement of operatives and vehicles
- Site hoarding or fencing, site security and safety of workers and public
These temporary works designs evaluate the structures for load bearing capacity, the installation and removal process of the structures, safety compliance, cost effectiveness and prevention of excessive movement or collapse.
For deep excavations, a temporary works design is required for any excavations exceeding 1.2m. Each temporary works design includes:
- An investigation of the ground material/condition, excavation width and depth, site location and any other necessary calculations are taken
- Load calculations, calculations of the proposed design and detailed drawings are outlined
- Method statements and risk assessments are produced to show a comprehensive analysis and breakdown of the procedures for installation, inspection and removal
- Compliance checks are undertaken to ensure local building codes, H&S regulations and industry standards are met
- Inclinometers and ground settlement markers can be installed to monitor any movement in the structures and detect risks early on
For all of the reasons listed above, our operatives and management staff understand the importance of temporary works designs and take all the necessary precautions when performing works involving a temporary structure.
Permit to Excavate
For any excavation our site supervisors are required to submit a permit to excavate form through our app to ensure that the correct order of proceedings and relevant checks have been made before penetrating the ground.
Each permit to excavate form outlines important project information, makes sure that all relevant risk assessments and method statements are present in the site H&S file and the area has been correctly CAT scanned with a calibrated CAT4E scanner and a qualified operative. Any services that were previously unmarked are to be reported to the site manager. All permits are approved by the client and filed before works start.
Other Considerations
There are a lot of considerations when performing deep excavations. Our experienced and well-trained operatives and management team are well equipped to take reasonable precautions and act appropriately when encountering difficulties.
At the start of the project a ground investigation report is undertaken to establish the quality of the ground, any contaminants in the soil are identified and the groundwater presence. These factors all effect the planning and procedures when breaking ground.
There are a number of excavator modifications and attachments that we implement for specific tasks that require extra measures to be taken or if it can increase productivity. For example, if there are overhead cables on site then excavators are fitted with height restrictors to avoid any chance of a collision with a cable. Excavators can also have structural modifications such as a long-reach arm to extend the arm further into a deep excavation or a shortened boom and arm for operating whilst the machine is inside an excavation(confined space).
Before any works commence, an emergency rescue plan is completed. This outlines:
- All rescue equipment
- Potential hazards
- Risk evaluation
- Emergency response steps
- Evacuation procedures
- Incident reporting
- A location plan for isolation of any services
All of these measures are essential to the H&S of our operatives