Safety evo
Life saving tips
Excavation workers may know that type C soil is the least stable soil
But based on that, what can they do to secure their work ?
Works need to be accomplished whatever the risks are.
But the role of safety is to secure every activity using the proper means.
The selection of the most proper controls starts with hazard identification.
In this post, let us answer the following questions.
Why we need to know soil classification ?
What makes it crucial to know what class of soil we are working on are two reasons.
First is to plan the activity properly by selecting the suitable excavation technique
and excavation tools used
The other reason is for safety
As the difference between soil classes is related to their stability
A less stable soil means that it is more likely to collapse
This can help the workers to choose the most efficient controls to avoid cave ins
And save themselves from engulfment hazards.
There are many construction solutions that can be used to secure excavation
Each control is best used for a certain soil class, this can be determined when we know the soil class.
Type C soil requires more safety precautions as it is the least stable soil class.
What are the Excavation soil types ?
According to their stability, OSHA classified the soil into tree main classes.
And the stability here means the ability of soil to resist collapse.
The unit used to measure stability is tons per square foot (TSF)
Class A soil
Class A soil is the most stable soil. It has the least cave in risk
Clay and sandy clay are common examples of type A soil.
The soil stability is more than 1.5 TSF.
OSHA determined some conditions to consider this soil type A.
If the soil was fissured, subjected to vibration or has been disrupted it cannot be type A.
Class B soil
The stability of Class B soil is greater than 0.5 TSF but less than 1.5 TSF.
Angular gravel, silt and silt loam are some examples of type B soil
Also, the previously disrupted soil can be considered type B soil
And in some situations, fissured soils or that exposed to vibration with the stability of type A soil (more than 1.5 TSF)
Class C soil
If the unconfined compressive strength of soil is 0.5 TSF or less, they are considered type C.
Granular soils like gravel and sand and soil where water is freely seeping are type C.
We can consider also the material in a sloped excavation where the slop is (4H/1V)
What are Type C soil characteristics ?
The following are the properties and characteristics of type C soil:
- Low strength soil (the compressive strength less than 0.5 TSF)
- Poor cohesive soil, meaning that the bond between the particles is weak.
- High water content can weaken the bonds between the soil particles.
- Type C soil is Granular in nature.
- This cannot withstand even minor vibration or small slopes.
- Remember that even other cohesive soils can be considered type C
If they were exposed to aggressive vibrations or fissures.
How to secure type C soil ?
It was mentioned before the different ways for excavation protection.
Just as a reminder, we can do either shoring, Shielding, Sloping or benching.
The type of the soil determines the proper protection way and how to implement it.
For example, we cannot implement a sloping process for type C soil the same way for Type A.
The following table is describing the slop angle and ratio for each soil class as OSHA says.
One of the most commonly used way nowadays is Hydraulic shoring.
It can fit all types of soil because of its great advantages.
While OSHA does not recommend Benching for type C soil.
So, the selection of the most effective protection way depends mainly on the soil type
and the worksite nature, as sometimes the narrow work place cannot allow sloping
in this case, the most suitable way is hydraulic shoring.
Special Health and Safety Considerations for excavation are also needed
And we promise to discuss these precautions in a separate post ASAP.
Until this time, you can visit our related posts for more excavation safety tips
