How to Prevent a Trench from Caving In

22 September 2015
 Categories: , Blog


You may be worried that the drainage channel that you want to excavate on your property will cave in and injure you or those working for you. Read on and learn how professionals will handle the job to prevent this risk from happening.


Sloping refers to a technique of digging the trench at an angle instead of digging straight down. This descending angle reduces how much pressure is exerted onto the sides of the trench by the surrounding soil. For instance, you can make the upper parts of the trench wide then reduce the width as the depth of the trench increases. The narrower part below has more firm soil around it, so it will be less likely to cave in.


Benching refers to creating levels that look like benches. It is an improved form of sloping, since it creates levels (steps) within the trench. The pressure exerted by the surrounding soil is shared by the levels created, and the chances of a cave-in are reduced since each level will handle a limited amount of pressure.


The two measures above may not be very helpful if the drainage excavation exercise is aimed at digging a very deep channel. For instance, benching will make the lower parts of a deep excavation so narrow that the excavation may not serve its purpose. Shoring helps to keep a channel wide enough but safe for those working down there. Shoring involves using vertical, horizontal and cross braces to hold the sides of the trench/drain channel so that it does not cave in.

You need to know the type of soil at the site so that you design a shoring mechanism that is suited to the conditions present at the site. For instance, silt is a combination of sand and clay soil. It easily absorbs moisture and it cracks as it dries up. Such soil may need a more extensive shoring system than clay soil that absorbs very little water, because it has particles that are densely packed together. Thus, clay is less likely to cave in due to water ingress, unlike silt. That is why silt needs more shoring than clay.


A trench shield is a complete structure that is placed within a trench to prevent it from caving in. The shielding device may be portable, or it may be immovable. The portable one can be moved from one work site to another while the immovable one is destroyed as it is being removed from where it was placed.

Each jurisdiction has regulations aimed at making drainage excavation a safe activity for workers and the general community. The risks are serious and that is why you should let trained personnel, like those at Minpex Drainage, who understand the techniques for a safe excavation perform the excavation, so that you do not take unnecessary risks.