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How Temporary Works Design Can Give Excavation Works A Solid Foundation

What is Temporary Works Design, and how can it help you get your construction project off to a successful start?

Posted 24 January 2024 by the SEL Team

Excavations are an important first step in any construction project. Whether the site is large or compact, this process is essential for site preparation and to lay solid foundations before a construction project can commence.

No construction job or site is the same and therefore excavation works can face many complications. Forward planning is a key component to avoid pitfalls and ensure the success of this part of the construction programme.

Temporary Works Design, done in consultation with a reputable Engineer, is a means to secure the desired outcome. It can give your construction job that solid foundation to deliver a successful and safe method. At Site Equipment Ltd (SEL), we always recommend getting an expert Engineer’s solution for on-site construction works.

What Is Temporary Works Design?

Temporary Works Design is about forward planning. It can be applied to a number of construction jobs, such as formwork, structural support and groundworks, which include excavations.

By definition, “Temporary Works”, is a widely used expression in the construction industry for an “engineered solution”. It is used to support or protect an existing structure or the permanent works during construction; to support an item of plant or equipment; the vertical sides or side-slopes of an excavation; to provide access.

Depending on the construction job and the nature of the site, the site excavation phase of the job can become rather complicated. Therefore the expertise of an Engineer could be a good investment.

Temporary Works Design provides assurance to the safety and buildability of a solution used on site; often, designs are required to satisfy Health and Safety requirements, but can also be instrumental in a Contractor’s method statement and risk assessment (RAMS) – it generally gives the Contractor the confidence to do the job.

Depending on the construction job and the nature of the site, the site excavation phase of the job can become rather complicated; therefore, the expertise of an Engineer could be a good investment.

Planning Excavation Works Is About Safety

Key considerations when it comes to planning your excavation works should include the type of excavation needed for the job, the equipment needed for the type of excavation required, and any health and safety measures to put in place for the safe execution of the excavation works.

According to the Health & Safety Executive (HSE), every year many people are either seriously injured or killed during excavation works by collapses and falling materials. 

Site workers are at risk from:

  • Excavations collapsing, resulting in being buried under soil and debris
  • Incurring injury from such a collapse
  • Materials falling in from the sides into an excavation
  • People or heavy Plant falling into excavations.

As an example, accidents can occur when site workers have not considered the risks from an open excavation and attempt to dig without adequate or any shoring and/or where shortcuts are being taken.

An Engineer designing your excavation works through a Temporary Works Design will review and recommend the equipment best suited to the job and the safest way forward for the type of excavation required.

What To Consider When Instructing An Engineer For Temporary Works Design

Standards Matter.

When instructing an Engineer where Temporary Works Design is required, it’s important to check the standards that are being worked to. At Site Equipment Limited (SEL), the Engineers work to the BS5975 UK standard for Temporary Works Procedures and Design.

The BS 5975 Standard provides recommendations and guidance on the procedural controls to be applied to all aspects of temporary works in the construction industry; it also gives recommendations and guidance on the design, specification, construction, use, and dismantling of falsework.

The main role of the engineers designing Temporary Works is, ultimately, to provide safe and buildable projects that “design-out” risks as much as possible.

The other standard to consider is ensuring the engineer works to the Construction Design Management (CDM) regulations; the Construction Design Management Regulations 2015 aims to positively impact health and safety in construction.  CDM regulations were developed to prevent construction accidents and fatalities; the regulations ensure that all tasks are carefully planned from start to finish and that all staff are competent to perform the tasks allocated to them.

The main role of the engineers designing Temporary Works is, ultimately, to provide safe and buildable projects that “design-out” risks as much as possible.

Engineer’s Considerations For Excavations

When it comes to excavations, the engineer will in the first instance determine the ground conditions, any underground structures and water courses, and the location of existing services.

The key issues the engineer would consider when planning out the design for Temporary Works for excavations will also include:

  • Collapse of excavations
  • Falling or dislodging material
  • Falling into excavations
  • Undermining nearby structures
  • Underground and overhead services
  • Inflow of ground and surface water
  • Damage to trees
  • Other aspects of excavation safety

Correct Equipment For The Type Of Excavation

The engineer will also decide on and recommend the best equipment needed for the type of excavation; for example, when you need to support deep, vertical-sided excavations, a safe solution would be excavation bracing struts – the brace excavation systems from Site Equipment Ltd (SEL) can provide temporary support to ensure that the site team is safe throughout all stages of the work. 

Depending on the job, the Engineer will be able to provide solutions from the complete range, which includes the Single Acting Brace System, the Double Acting Brace System and the H-Series Double Acting Manhole Frame.

The Single Acting Brace System

This is light and simple to use and ideal for excavations with a sheet-to-sheet range of 1.8m to 2.7m and where a small machine is being used – the excavation can be up to depths of 3 metres in good ground. The Single Acting Brace System utilises a simple pin-and-joint connection method to brace the trench or hole; consisting of a series of single piece hydraulic legs, the system is easy to assemble and can be installed and disassembled on site.

The AA brace system available from Site Equipment Ltd (SEL) offers a max permissible load of 38 kN/m.

The Double Acting Brace System

The Double Acting Brace System is a robust and adaptable solution that can be used for excavations, such as the installation of an earthwork support system to maintain a safe working environment for the construction of pumping chambers and manholes.

The Double Acting Bracing System features legs, which can be interchanged to form the correct brace dimensions; for example, Type A legs (2m to 3m) and Type E legs (6m to 7m) form a brace which is 7m x 3m.

Site Equipment Ltd (SEL) has a range of sizes and systems available with sheet-to-sheet ranges from 2m to 7m and permissible loads up to 65 kN/m to suit the requirements for the job.

The H-Frame Series Double-Acting Manhole Frame is a robust and high-capacity shorting system

H-Frame Series Double Acting Manhole Frame

Designed for larger excavations, the H-Frame Series Double Acting Manhole Frame is a tried and tested bracing system with interchangeable manhole brace leg sizes; this high-capacity shoring system is an extremely robust and adaptable system that can be used alongside trench sheets to create manholes or larger tank excavations at depth.

When digging excavations, always remember to take into account the measurements for the Trench Sheet pan depth as well as the Manhole Frame section – the engineer at Site Equipment Ltd (SEL) will be able to recommend the correct system and dimensions required.

Equipment Safety

 All the equipment is regularly checked by the experienced team at Site Equipment Ltd (SEL), meets the relevant health and safety standards and is complete with test certificates where applicable.

The engineers at Site Equipment Ltd (SEL) will also supply the relevant technical drawings and calculations to ensure that the appropriate bracing system is used for the job. Calculations will also take into account surcharge loads from roads, railways, and buildings. It is then the Contractor’s responsibility to implement the woks correctly according to the recommendations, drawings, and calculations supplied.

Contractor’s Responsibilities

It is the Contractor’s responsibility to implement the Temporary Works Design correctly and for the works to be managed by the Temporary Works Co-ordinator or Temporary Works Supervisor on site.  The Temporary Works Co-ordinator takes responsibility that what has been installed is correct to the drawing and to issue a Permit to Work or a Permit to Load if the temporary works is supporting something.

Site Equipment Ltd (SEL) also provides demonstrations on site if further assistance is required.

How To Instruct An Engineer For Temporary Works Design At Site Equipment Ltd (SEL)

Give your construction programme the best start with a Temporary Works Design for excavation works. You can enquire about the engineer’s solutions provided by SEL by contacting the nearest SEL depot or by calling 0117 982 8236.

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