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Getting the correct trench shield configuration is a combination of maths and physics

The depth, width and length of the trench, along with differing locations, soil types, equipment on site, site access, compliance, and sustainability, all need to be factored in.

Flexibility covers all bases

Trench shield options are available in a full range of widths and sizes to suit individual projects – whether it’s a small utility manhole or a kilometre-long sewer line.

No two jobs are the same which is why trench shields come in a wide range of sizes, some stackable, some with “feet”. Trench shields can also be configured to provide protection for pipe thrusts (thrust boring) where only a three-sided solution may be required.

Depending on project size, trench shields can be used as either ‘open’ trench shields or ‘closed’ box shields.

Over 200 configurations of trench shields are available.

The following tables summarise the top configurations, including what the configuration looks like and when it would be used for our 4 most popular shield types:

1.   2.4m trench shield

2.   3.6m trench shield

3.   2.4m manhole box

4.   2.4m modular manhole box

2.4m Trench Shield

Guardian aluminium trench shield 2.4m Long x 1.2m high — mostly used in shallow trenches for a safe working area when laying pipes. Suitable for all soil types within the kPa rating.

Shield Configurations Overview

1. Standard Shield

What You Need

• 2x 2.4m long by 1.2m high panels

• 4x struts (there are different sizes from 0.6m to 2.5m)

• Pins & R clips

What It Looks Like

Two side panels with struts holding panels apart.

Common Use Cases

You would use this in a common small trench that is 1.2m deep and has an internal width of 0.6-2.5m, for laying or fixing pipes.

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2. 3 Sided

What You Need

• 3x 2.4m panels

• 2x 1.2m struts

• 4x corner brackets

• Pins & R clips

What It Looks Like

Three-sided shield box placed on end with corner brackets to join the back panel to the side panels, and struts holding the panels apart at the front, making a 1.2m square box open at one end that is 2.4m high.

Common Use Cases

This is normally used when fixing laterals, putting a small manhole in or butting up against another shield, at the end of a row of shields.

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3. Vertical

What You Need

• 2x 2.4m long by 1.2m high panels

• 4x struts (there are different sizes to choose from)

• Pins & R clips

What It Looks Like

Two side panels with struts holding panels apart, placed on end to make the shield 2.4m high by 1.2m long.

Common Use Cases

This type of shield would be used in a deeper and skinnier 2.4m deep and 1.2m wide trench or used to be put between laterals in a larger job.

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4. Box

What You Need

• 4x 2.4m long by 1.2m high panels

• 8x corner brackets

• Pins & R clips

What It Looks Like

2.4m long by 1.2m high panels are joined at each end to make a square box shape.

Common Use Cases

This box would be used to put in a shallow (or not so shallow if stacked) manhole or tank in the ground.

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5. Stacked

What You Need

• 4-6x 2.4m long by 1.2m high panels

• 8-12x struts

• 4-8x vertical joiners

• Pins & R clips

What It Looks Like

Two or three lots of two side panels with struts holding panels apart, stacked on top of each other.

Common Use Cases

You would use this for laying or fixing pipes deeper in the ground in a common small trench that is 2.4m or 3.6m deep if stacked 3 high.

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3.6m Trench Shield

Guardian aluminium trench shield 3.6m long x 2.4m high — designed for use in subdivisions where space is tight and also used on larger jobs with bigger pipes and machines. Heavy Duty and well-constructed for larger jobs. Can also be moved with a smaller machine. Not recommended for running sand.

Shield Configurations – Larger Setups

1. Standard Shield

What You Need

• 2x 3.6m long x 2.4m high panels

• 4x 0.6–3.5m struts

• Pins & R clips

What It Looks Like

Two side panels with struts holding the panels apart.

When to Use

This would be used in larger job that would be laying larger pipes or longer lengths.

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2. Shield with Topper

What You Need

• 2x 3.6m long x 2.4m high panels

• 2x 3.6m long by 1.05m high extension panels

• 6x struts

• 4x vertical joiners

• Pins & R clips

What It Looks Like

Two side panels with extension box attached to the top with vertical joiners and struts holding all the panels apart.

When to Use

The extensions are used to add on top of the shields, to make it taller, so you can have a deeper trench and still be protected. This makes the total height 3.45m.

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3. Box

What You Need

• 8x 3.6m long by 2.4m high panels

• 16x corner brackets

• 8x vertical joiners

• You don’t have to stack 2 panels high, you can just do it just one layer high which would need half number of panels, corner brackets and no vertical joiners.

• Pins & R clips

What It Looks Like

3.6m long by 2.4m high shield box made of 4 medium shields stacked on top of another four medium shields, configured the same way all joined together to make a safe trench box.

When to Use

This is for larger Manholes or Tanks, or can be to get small machinery into the trench to excavate deeper.

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4. Shield with High-Rise Struts

What You Need

• 2x 3.6m long x 2.4m high panels

• 4x high-rise struts

• 4x strut joiners

• Pins & R clips

What It Looks Like

Two side panels with high rise struts holding the panels apart.

When to Use

This is used when you are put in large diameter pipe and need more clearance to work under.

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2.4m Manhole Box

Guardian aluminium manhole box 2.4m wide x 2.4m long x 2.4m high — used for installation and maintenance of manholes. Suitable for any soil type within kPa rating.

Shield Configurations – Box Setups

1. Box

What You Need

• 2x 2.4m long by 2.4m high U-shaped panels

• 4x fixed struts

• Pins & R clips

What It Looks Like

A square, almost fully enclosed box with four struts in 2 set pockets, holding the panels apart.

When to Use

These are commonly used to install 1050–1500mm manholes or similar size tanks.

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2. Adjustable Box

What You Need

• 4x adjustable 0.8–1.2m, 1.2–2.0m, or 1.4–2.4m struts

• 2x 2.4m long by 2.4m high U-shaped panels

• Pins & R clips

What It Looks Like

A square, almost fully enclosed box with a total of four adjustable 0.8–1.2m, 1.2–2.0m, or 1.4–2.4m struts holding the two U-shaped panels apart.

When to Use

This would be used to adjust the 2 sides with the gap in it to make it smaller or larger, as the pipe may differ. Also, with different size tanks you can make it longer one way, for example one side would be fixed 2.4m and the other side can expand to 3.6m.

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3. Stacked

What You Need

• 4x 2m long by 2m high or 2.4m x 2.4m U-shaped panels

• 8x fixed struts

• 4x vertical joiners

• Pins & R clips

What It Looks Like

A square, almost fully enclosed box with eight struts holding the four U-shaped panels apart. Stacked 2 high.

When to Use

These are commonly used to install 1050–1500mm manholes or similar size tanks that are being put deeper into the ground, e.g. 4m deep.

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2.4m Modular Manhole Box

Guardian aluminium modular manhole box — completely enclosed boxes, box with feet, 3 sided box, box with missing panels for pipes to pass through, or shield. These are ideal for running sand and installing manholes as they are light, flexible and easy to transport when not made up.

Shield Configurations – Modular Setups

1. Box

What You Need

One panel high box is made from:

• 4x individual panels

• 4x corner connectors

Or four panel high box is made up of:

• 16x individual panels

• 12x corner connectors

And so on.

• Pins

What It Looks Like

A square, 1 to 5 layered fully enclosed modular box with four sides.

When to Use

This is used to install a manhole or tank into the ground, depth can range from 0.6m to 3m deep box. Because it is modular you can use a smaller digger to lift parts around and make it as you are digging the hole out.

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2. Box with Legs

What You Need

4-panel high box with legs is made up of:

• 16x individual panels

• 12x corner connectors

• 4x legs

• Pins

What It Looks Like

4-layered, fully enclosed modular box with four sides, and legs to hold it up off the ground.

When to Use

This is used when you have pipes crossing over at the bottom, or if you are connecting a new pipe coming into a manhole, or can just be to lift 600mm up to make room for working in or laying material in.

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3. 3 Sided Box

What You Need

• 9x modular panels

• 4x corner connectors

• 2x modular struts

• 4x shield connectors

• Pins

What It Looks Like

A square, 3-layered, enclosed on three sides modular U-shaped box with two modular struts holding the shield sides apart on the open end.

When to Use

This type of shield would be used if you are laying a large pipe into a manhole, if you are needing one side open for drill shots or thrusting, or can be used for end of the trench caps.

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4. Missing Panels

What You Need

• 14x modular panels

• 12x corner connectors

• Pins

What It Looks Like

4-layered, fully enclosed modular box with four sides, and one (or you can do more) panels on the bottom layer taken out to create space under the shield.

When to Use

You would use this when installing a new manhole and have pipes running in or out of it, or if laterals are crossing through.

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5. Modular Shield

What You Need

• 10x modular panels

• 8x modular struts

• 16x shield connectors

• Pins

What It Looks Like

5-layer modular shield with only two enclosed sides and four modular struts at each open end, keeping the shield sides apart.

When to Use

This is used for when laying pipe and you are needing certain sizes between pipe or laterals, or can be used if you have a smaller site and needing a lighter and easier shield to manhandle.

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Struts are a contractor’s superpower

Struts (and adjustable spreader bars) allow trench shields to be adjusted to varying widths to suit a particular job or even changing widths within a trench. They ensure that the trench shields have the correct support to do their job.

Adjustable spreader bars will shore numerous different trenches with a telescopic strut system minimising the gaps between shields and the trench sides, to prevent unnecessary movement of the shield. This is especially handy when working around services.

Most shields can be set up in different configurations. The most common panels used are listed in the graph below with their most common strut sizes. Various strut sizes are used to accommodate many different pipe sizes and positions.

Practical applications

Click the following link to see how different Guardian trench shields helped Fulton Hogan:

https://www.transquip.co.nz/blog/guardian-supporting-the-fulton-hogan-teams-down-in-the-trenches

By WorkSafe New Zealand guidelines, any trench deeper than 1.5 metres is considered high risk and must be shored, battered, or benched, unless a competent person (e.g. a geotechnical engineer) has assessed and confirmed it’s safe without it. Our Guardian experts would go further and say that any time a worker’s head is below ground level (when bending down or kneeling), there should be a certified trench shield in place, as even a collapse in a shallow trench can be very dangerous.

Little to large

Popular 2.4m x 1.2m trench shields are an excellent maintenance unit that fits on the back of a Ute. These can be assembled or dismantled in minutes and carried into backyards or restricted areas.

Click to see Huntley and Harley, the Guardian experts demonstrate how to make a small shield: https://www.transquip.co.nz/blog/Learn-how-easy-it-is-to-make-up-a-2301-Lightweight-Aluminum-Trench-Shields

3.6m trench shields are also frequently used, along with modular manhole boxes – which protect workers while permanent manholes are installed.

Click to see Huntley and Harley, the Guardian experts demonstrate how to make a modular box: https://www.transquip.co.nz/blog/Learn-How-To-Make-the-Guardian-Modular-Trench-Shields-video

Click to see Huntley and Harley, the Guardian experts demonstrate how to make a large trench shield: https://www.transquip.co.nz/blog/Learn-How-To-Make-the-Guardian-Modular-Trench-Shields-video

The Guardian team are always on hand, for advice. Or for regulations, click here https://worksafe.govt.nz/topic-and-industry/excavation/excavation-safety-gpg/

Call us today on 0508 41 41 41 to discuss your needs or check out our extensive product range for hire/ buy here: https://www.transquip.co.nz/Hire

Disclaimer: All Guardian products are engineered and manufactured to comply with applicable industry standards and safety regulations in New Zealand, including those related to excavation support and ground stabilisation. However, it is the sole responsibility of the end user to ensure that all equipment is used correctly, safely, and within the limits for which it is designed. By purchasing or using our products, the user acknowledges and accepts full responsibility for ensuring the equipment is used appropriately and in compliance with all applicable regulations and best practices. Always consult a qualified engineer or competent person before use.