To help you decide what large trench shield is best for your needs, we compiled a list of shields that are the most popular sizes and strengths we get asked about.

This article explores the benefits of each shield and how they can help you in different real-life situations. Please note that this blog does not list the shields in any particular order and all information is to the best of our knowledge. 

How these features help in real life: 

Size & Project size: This affects the size projects the shield would suit. Smaller shields are better because they are lighter, easier to use, and move around compact sites. Also, normally (depending on material and how the shield is made) the smaller the shield the lighter the machinery needed. The larger the shield, the more efficient for large-scale projects as you can set up one shield instead of multiple in a long trench, speeding up project timelines and saving money on hiring multiple shields.

Load Capacity: The load capacity is determined on the strength of the shields and is shown in the kPa ratings. Load capacity is determined on many things, like thickness of shields, length of shields, material type, grades and most importantly the design. The design of the shield is the most importance factor as it affects all variable of a shield eg some small smartly designed shields can have a higher kPa than poorly designed large shield.

A civil engineer would need to check the ground conditions at the site to determine the kPa rating required for shields.

Weight & Recommended Machine size: The heavier the shield the larger the machine is required to be able to lift it. The rule-of-thumb calculation we use for the recommended machine sizes is 5.5 times the weight of the shields. For example, a shield weighing 1 tonne would require a 5.5 tonne or more digger to lift it. The smaller shields are lighter and easy to use in smaller urban areas and cost less. Whereas larger shields are heavier, more heavy-duty and are built to be handled with larger machines.

Material: This affects a range of things including the weight and portability, corrosion resistance, strength to weight ratio, cost effectiveness certification and long term effect of damage.

Lifting Points: These are where the hooks on lifting chains would attach to, when moving a shield around. Not all shield designs have these built in. Some designs also have less points than others to use which gives less flexibility as to how you lift the shield.

Stackable: If you need to create a deeper trench configuration (like the pictures below), you can stack the shields as needed, adapting to project requirements. Please note when stacking shields, they can only go to their max depth capabilities. If the shield’s max depth is exceeded, you are exposing yourself to the risk of the shield failing and collapsing, putting workers at risk and having potential fatalities.

Max depth: The max depth is the deepest the shield can go in the ground for based on its kPa rating, because as you go deeper, the greater the ground pressure against the shield becomes. Generally speaking, the higher the shield kPa rating, the better, as they are stronger. However, this strength comes at a price as it can increase the weight of the shield, which is not always the most efficient approach.

Wall thickness: Thicker walls enhance the shield's durability and allows them to withstand larger amounts of pressure. This is why longer shields have thicker walls. The thinner the walls the better, as they have more internal working space, but a trade-off of them becoming longer is that this usually makes them weaker giving a lower kPa rating.

 

Strut Type & Size: There are 3 different options which all have pro’s and cons.

Solid struts have less parts and are easier to use, lighter and easier to fit to the shields with no moving parts. They are generally also cheaper.

Adjustable strut gives you the flexibility to accommodate various trench widths ensuring the right fit for more jobs and for unexpected changes to your trench width when digging. These cost more than solid strut. And are heavier.

Hire rise stuts are specifically designed so that the under strut clearance is higher. If you're working with pipes larger than 1.35m you may need to consider using these as they increase clearance to 1.9m. There are more parts to these and they weigh a lot more than the other kinds, so they take longer to set up and a larger machine would be required. These cost a lot more also.

Under Strut Clearance: This is the distance from the bottom strut to the bottom of the shield. The larger the shield the more that can fit under it making it easier to fit pipes. You need to take this into consideration if a pipe being laid has a large Diameter or is longer. For example, on the 2375 shield, there is a 1.35m clearance which means that’s the biggest pipe diameter you can lay under it. So this is when you would have to increase this height & somethines width of the shield to fit the pipes under it.

User Friendly: A user-friendly shield has less components and less room for error. Most shields that are easy to use typically will only need the shield panels, struts, pins and R-clips so can easily be put together by any contractor. Shields that are not so user friendly may involve making sure everything is 100% lined up, or special equipment is needed to put them together, and lot more parts to make them, which normally increases the weight. The easier it is to use and make, the less time it takes; it also means that you can transport the shield as panels meaning less bulky transport. 

Certification: Each country has guidelines on what specs the shield needs to meet. All our shields meet British, European, Australian and New Zealand standards, with the European standard generally recognized as being the highest. Find out more about what these standards mean here https://www.transquip.co.nz/blog/extreme-shield-testing

 

What trench shield suits your unique project requirements?

Whether you need a lightweight shield for tight urban spaces, a high-capacity solution for challenging soil conditions, or a versatile system for deeper excavations, Guardian has options to suit your needs.

Our team is here to help keep your crew safe and your projects moving. Explore our full range of trench shields or connect with one of our shield experts to find the best fit for your next job.

For North Island contact: ben.m@guardiancivil.co.nz

For South Island contact: ht@transquip.co.nz

Or call: 0508 41 41 41