In this blog, we explore the different methods contractors can use to make trenches safer, from traditional sloping and benching through to modern shielding and shoring systems. We walk through each approach, explaining where it’s best suited. Whether you’re working in wide-open greenfield sites or tight urban spaces, we cover practical ways to protect your crew. 

The first solution we are going to explore is sloping:

What is sloping?

Trench slooping is a method used to prevent trench walls from collapsing by cutting the sides of the trench at an angle, rather than leaving them vertical. This reduces the pressure from the surrounding soil and helps keep the excavation stable and safe for workers.

The angle depends on the soil type: hard clay can be a steeper slope than loose sandy soil. So the looser the soil the more room that is needed to slope the trench.

The second solution we explore is Benching:

What is benching?

Trench benching is a method of trench wall protection that involves cutting the sides of a trench into a series of horizontal steps, or “benches”, instead of a continuous slope. Like sloping, benching is designed to reduce the risk of trench collapse — but it does so by breaking up the soil pressure with staggered levels, rather than a smooth angle.

These steps, like stairs, reduce pressure on the walls and make the trench safer. Benching works best in strong, stable soils like clay (Type A or B), but it’s not safe to use in loose or sandy soil (Type C). It takes up less space than sloping but still needs to be done properly.

Both sloping and benching aim to reduce risk of collapse by moving the soil away from the trench to reduce ground pressure. This is mostly used where space isn’t an issue – greenfield developments for example. So, as long as the soils are a known quantity, and there are no aquifers, (which add another level of complexity and unpredictability) and suitable equipment is available, you’re good to go.

The third solution we explore is soldier sets:

What are soldier sets?

Trench soldier sets (also called vertical shores) are compact trench support systems used to prevent trench walls from collapsing, especially in tight or confined excavation sites. They’re made up of vertical rails (called soldiers) and adjustable or fixed struts that push out against the trench walls to hold the soil back.

This lightweight manual soldier is specifically designed for small contractors, such as drain layers, who may not always have access to heavy machinery on-site. Weighing only 38kg per 2.4m set, its manageable size allows for easy man-handling without the need for a digger, making it ideal for confined spaces and quick setups. Click this link to see soldier sets: https://www.transquip.co.nz/Guardian-aluminium-manual-soldier-set-3.0mH-with-0.6-0.9m-struts

Click this link to see hydraulic soldier sets: https://www.transquip.co.nz/Guardian-aluminium-hydraulic-vertical-shore-set-2.4mH-with-0.58-0.92m-struts

The fourth & most common solution we explore is shielding: 

What is shielding?

A trench shield is typically placed inside the trench after excavation. It commonly consists of two strong, parallel sidewalls or panels (usually made from steel or aluminium) held apart by fixed or adjustable struts or spreader bars. These walls act as a barrier between the worker and any collapsing soil for the full depth and length of the trench, from ground level down (and sometimes above!) Unlike sloping or benching, shields can be used in any soil type.

As our shields are lightweight aluminium, they are easy to move into tight spaces, which means you can work in much smaller areas and will save time digging out a slope or creating benches. This makes them ideal for established residential areas when there is a lack of working room.

Find out more about aluminium shields here: https://www.transquip.co.nz/Guardian-aluminium-trench-shield-3.6m-x-2.4mH-with-1.0m-struts

The fifth solution we explore is half shielding: 

What is half shielding?

A half-shielded trench uses two proven safety methods in one practical design. The upper section is sloped or benched to reduce the risk of surface collapse, while the lower section is protected with a trench shield where soil pressure is greatest. This hybrid approach keeps workers safe, reduces how much you need to excavate, and saves on materials — ideal for sites where space is limited but not at a premium. It still needs to be engineered appropriately, making sure the transition between slope and shield stays secure and compliant.

The sixth solution we are going to explore is modular manhole boxes:

What are modular manhole boxes?

Modular manhole boxes are extremely versatile and can be configured so they work as a trench shield, 3-sided box, or a completely closed box. 

They work the same as a shield holding the soil back from collapsing in on workers and have the ability to remove up to 2 bottom panels to allow for services or pipes to pass through unhindered while still protecting personnel inside.

These, like small shields can be easily assembled, dismantled and transported on a Ute or a trailer as the panels are lightweight and easy to handle. These are mostly used to install manholes or to keep out running sand.

Find out more about manhole boxes: https://www.transquip.co.nz/Guardian-aluminium-manhole-box-3.0m-x-3.0m-x-2.4mH-with-1.8m-struts

Find out more about modular manhole boxes: https://www.transquip.co.nz/Guardian-aluminium-modular-manhole-box-1.5m-x-1.5m-x-1.8mH

Not without risk

As contractors will tell you, almost every job is different and getting engineering advice, and understanding the variables (soil conditions etc) are vital.

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, though there’s still a lot to consider – if the worker’s heads are ever going to be under the surface of that trench, or they’re bending or kneeling to complete a task, we say they should have adequate protection.

To find out more about excavation safety click here: https://www.worksafe.govt.nz/topic-and-industry/excavation/excavation-safety-gpg/

To sign up for an excavation safety course click here: https://www.transquip.co.nz/blog/trench-shield-safety-training-course

Or call the team at Guardian on 0508 31 31 31. We look forward to talking to you.

Disclaimer:

This blog is for general information only and does not constitute engineering advice. Trenching conditions vary widely — always consult a competent person or qualified engineer before starting any excavation work.

TransQuip is not liable for any injury, damage, or loss resulting from the misuse or incorrect application of trench safety products mentioned here. Use equipment responsibly and follow all WorkSafe NZ guidelines and regulations.