Safety evo
Life saving tips
In this excavation safety toolbox talk, we shall discuss some techniques
by which we can ensure the safety of an excavation.
Excavation collapse became very common the last years.
For this reason, OSHA increased the safety precautions for trenching in US.
Excavation collapse is a form of engulfment hazards that can cost lives.
Let’s explain some of the most widely used excavation techniques.
Check them in the following elements list.
But first, we have to know the different soil types.
Soil Types
Soil can be classified into 3 main types according to their stability.
Type A, B or C.
Where type A soil is considered the most stable and type C is the least stable one.
And while excavation, you can pass through many types not only one.
Latter we will explain in deep the difference between each soil type.
But for now, enough to know that Type A is very cohesive like clay and sand clay.
There is a factor called unconfined compressive strength used in soil classification.
For type A, this unconfined compressive strength factor is more than 1.5 ton /square foot.
Unconfined compressive strength factor for type B soil is between 0.5 to 1.5 ton /square foot.
If this unconfined compressive strength is less than 0.5 Ton/square feet, this is type C soil which is least stable.
Now it is time to start what we are aiming through this excavation safety toolbox talk
and identify the 4 main methods to secure an excavation.
Shoring, Sloping, Benching and shielding
What is shoring
Shoring is done by installing a type of support to prevent soil movement .
It also can be used after earthquakes to stabilize the damaged structures.
there are many types of shoring:
One of these types is called soldier pile and lagging
where, soldier piles are inserted into the ground then wood planks are inserted to make a wall.
Other type, is pressure grouting, where concrete layer is injected into the soli
This concrete fills the cracks and stabilizes the excavation sides.
Hydraulic and pneumatic shoring can also be used, by using hydraulic jacks or air bags for supporting the excavation walls.
Sloping sides of excavation
This method is available if we have adequate space around the excavation.
The slope has a certain ratio, can be determined according to the classification of soil.
If we are trenching in a type A soil, the degree of slope is approximately 54 degree.
Here the ratio between width to depth is 3/4 to 1.
While, for type B, the ratio becomes 1 to 1. Same depth same width.
The ratio becomes 1.5 to 1 when digging in type C soil.
trench benching
It is the least common used type of protection.
It can be used only on type A and B soils
And it has the same limitation as the sloping, it needs wider space around the excavation.
OSHA classified benching into simple and multiple benching according to the depth.
benching systems are prohibited in type C soil as it is the least stable type.
Now, let’s move to the last type for today ……
shielding excavation
This one is the most effective way for excavation protection.
Used for all soil types, the most proper for narrow areas where sloping and benching cannot be implemented.
It is typically using a shield to prevent the soil collapse.
The main target of shoring is to protect workers from cave-ins and engulfment.
This method can be done using trench boxes.
Shielding can be used alone or side by side with sloping or benching if we need more protection layers.
This was just a small excavation safety toolbox talk
You can consider that it is the beginning and we promise we will provide more details later
Until this time,
