Excavation works
Personal Protective Equipment
In work of this kind, PPE that is appropriate for the existing risks must be used; especially a safety helmet, safety footwear, goggles, protective gloves and reflective vest.
Within excavation works, we distinguish between two differentiated cases: trenches and pits (which, on account of their reduced dimensions may make working inside them hazardous) and excavations.
Trench and Pit Works
This type of excavation is associated with the type of buried linear works that comprise the variety of infrastructure works for utilities, sewage and channelling, including the construction of gas pipelines, whose works add other characteristics resulting from the installation of large lengths of steel pipes that must be welded and X-rayed.
Works of this type involve opening up a trench in the ground and introducing pipes, positioning and joining these together and subsequently filling in with compacted earth, in addition to including the laying of foundations for building work. Being able to carry out these works from the outside without human intervention at the bottom of the excavation would avoid many problems and a large number of mortal accidents.
Meanwhile, however, until new technologies exist that avoid the presence of workers inside trenches and pits, we must use the means available to us to control risks in accordance with the stipulations of the Regulations in force.
Preventive measures in trenches:
Design:
- As a general rule, consider all excavations that reach a depth of 0.80 m in unstable ground and 1.30 m in stable ground to be hazardous.
- Minimum width/diameter of the trench or pit. For each depth and phase of execution that requires the worker accessing the trench or pit, there is to be a circle with a diameter ≥ 0.80 m between the shoring or executed works for him to move around in.
- In stable ground without stresses from roadways or foundations, for H < 1.30 m, vertical cuts may be made without shoring. For greater depths, shoring is to be installed or a suitable slope is to be cut.
- In loose ground that does not reach this depth or solid ground with stresses from foundations or close to a roadway, shoring is to be installed or a suitable slope for the trench walls.
- Stepped slopes may be used employing shoulders, with horizontal sections of no less than 0.65 m and vertical sections of no more than 1.30 m in slope cuts at angles of between 60º and 90º for an admissible height that depends on the apparent specific weight of the ground and its simple compressive strength.
Maximum admissible height in metres in vertical cuts, free of stresses, for different specific weights of ground.
| Simple compressive strength Ru in Kg/cm3 | Apparent specific weight in g/cm3 | ||||
|---|---|---|---|---|---|
| 2,20 | 2,10 | 2,00 | 1,90 | 1,80 | |
| 0,250 | 1,05 | 1,10 | 1,15 | 1,20 | 1,25 |
| 0,300 | 1,30 | 1,35 | 1,40 | 1,45 | 1,50 |
| 0,400 | 1,70 | 1,80 | 1,90 | 2,00 | 2,10 |
| 0,500 | 2,10 | 2,20 | 2,30 | 2,45 | 2,60 |
| 0,600 | 2,00 | 2,70 | 2,80 | 2,95 | 3,10 |
| 0,700 | 3,00 | 3,15 | 3,30 | 3,50 | 3,70 |
| 0,800 | 3,40 | 3,60 | 3,80 | 4,00 | 4,20 |
| 0,900 | 3,90 | 4,05 | 4,20 | 4,45 | 4,70 |
| 1,000 | 4,30 | 4,50 | 4,70 | 4,95 | 5,20 |
| 1,100 | 4,70 | 4,95 | 5,20 | 5,20 | - |
| > 1,200 | 5,20 | 5,20 | - | - | - |
| Maximum admissible height in metres (H max.) | |||||
- It is also advisable to install shoring when using more pronounced slopes than are appropriate for the characteristics of the ground, or when executed with shoulders that do not satisfy the aforementioned conditions.
