Question 1

What is a Trench Box?

Accepted Answer

A Trench Box is a structure usually consisting of two walls or panels; its purpose is to protect workers from injury in the event of an excavation collapse. Different sized Trench Boxes can be used depending on the depth and length of the excavation, and a range of strut types accommodate the width. Core components of a Trench Box typically include:

Steel or aluminium panels
Top Boxes, depending on the excavation depth
Spindles or struts, either incrementally or fully adjustable
Strut and Top Box pins and connectors

Question 2

What size Trench Box do I need?

Accepted Answer

The required size of Trench Box will firstly be determined by the size of the excavation: Groundforce supply four trench box sizes, all with adjustable struts. Mini Trench Boxes start with a plate length of 3m, and the Mega Trench Box has 5m plates. All Trench Box sizes can be fitted with a top box to achieve greater depths. Other factors that influence the size of a Trench Box include:

Type of soil (sand, silt etc.)
Any utilities work within the trench
Excavator size (weight limitations)

Question 3

What does a Trench Box do?

Accepted Answer

A trench box holds back the earth on two sides but is open at its ends. Using more than one trench box can facilitate the installation of long pipe runs or similar, as they can run parallel to one another.

Question 4

When should a Trench Box be used?

Accepted Answer

A Trench Box should primarily be used to protect workers from excavation wall collapse while undertaking groundworks. Ease of installation means Trench Boxes are the industry’s first choice for the rapid shoring of excavations and extended trench runs. Trench boxes can be used in most ground conditions but are not recommended for use in unmanaged, waterlogged ground.

Question 5

How much does a box weigh?

Accepted Answer

The aggregate weight of a trench box will essentially be determined by the size of panels used together with the type of struts and associated accessories. In conditions where a lightweight solution is required, the Groundforce range of backhoe trench box products provide an excellent option. All our user guides provide information on the weights for different configurations of boxes and this is useful to know for transportation purposes, but also essential information for the hirer as it dictates the excavator class and capacity required in order to lift or position the box.

Question 6

Can a trench box be stacked?

Accepted Answer

Depending on the soil pressures acting on the panels, a trench box allows for up to two additional top boxes to be stacked on the base box. A simple connection system using a cassette and pin system quickly and easily connects the boxes.

Question 7

How do you install a trench box?

Accepted Answer

On site, the trench box panels and struts will be safely assembled at ground level prior to setting in the partially dug trench. The trench box can then be installed using the traditional dig and push method, connecting any additional top boxes as the excavation proceeds and finally fitting any edge protection barriers.

Question 8

How deep can a trench be without shoring?

Accepted Answer

Regardless of depth, we recommend shoring equipment is installed in all excavations and that a site specific risk assessment is carried out.

Question 9

What is the difference between a trench and an excavation?

Accepted Answer

An excavation is any hole in the ground, of any shape. A trench is similar but is linear in nature.

Question 10

Does a trench box prevent cave-ins?

Accepted Answer

Yes, providing a temporary works design has demonstrated that the box is suitable for the specific application and ground conditions present.

Question 11

What depth do you need a Trench Box?

Accepted Answer

What depth a Trench Box should be ultimately comes down to the engineer’s design and any site specific requirements. If pipes and utilities are being installed this will also be factored into the depth requirement. Trench Boxes can be installed leaving an upstand to provide a safety barrier which will also determine the overall depth.

Question 12

How do I build a Trench Box?

Accepted Answer

Assembling a Groundforce Shorco Trench Box is a simple process due to its modular design and minimal components. Typically a plate is laid on the ground and 4 pre‑adjusted struts are secured with pins to face upwards. The second plate is then raised and lowered onto the struts, completing the assembly: the Trench Box is then ready to be manoeuvred and placed into an excavation.

Question 13

Why hire a trench box?

Accepted Answer

The modular design of Trench Boxes means the equipment can be assembled and installed very quickly to get your project moving without fuss or delay. In contrast, fabricated shoring solutions involve costly equipment, skilled welders and more time to implement. Modular Trench Boxes however benefit from cost‑effective versatility together with built‑in design features that comply with safety legislation. Trench Boxes can also be easily relocated onsite as a project progresses.

Type	Mini Multi Box		Standard Multi Box		Mega Multi Box
Type	Base	Top Ext	Base	Top Ext	Base	Top Ext
Plate Length (m)	3.0		3.5		5
Plate height (m)	2.0	1.0	2.6	1.3	2.6	1.3
Plate thickness (mm)	60		100		127
Overall trench width (m)	0.66 - 4.41		0.73 - 4.53		0.79 - 3.90
Internal width (m)	0.54 - 4.29		0.54 - 4.29		0.53 - 3.64
Weight (kg)*	1160	632	2084	1232	3090	1840
Distance between struts	2.50		3.0		4.53
Strut Clearance Height (m)	1.19	N/A	1.44	N/A	1.4	N/A

Groundforce Verbaulösungen

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Trench Box: Typical Installation Methodology

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