Earthworks - excavations

Earthworks
(excavations, preparation of the construction site, reclamation, land improvement)

The rules for assuring occupational safety and health during the performance of earthworks are governed by the Resolution of the Minister of Infrastructure of 6 February 2003 on occupational safety and health during the performance of construction works (Journal of Laws 2003, No. 47, item 401)


Earthworks related to the erection of a building include: excavations produced in order to build foundations and basements and also excavations for various types of installations.
The most frequent threats that appear include:
  • Burying workers as a result of the collapse of the walls of the excavation (serious accidents have been recorded, even in excavations of a depth of up to 1 m - on an inclined terrain)
  • Falling into the excavation e.g. as a result of being hit by a moving part of a construction machine (e.g. excavator scoop), landslide on the edge of the excavation or slipping
  • Falling lumps of soil, rocks etc. onto those working in the excavation.
One of the fundamental requirements of occupational safety and health is the obligatory securing of the walls of the excavation of a depth greater than 1 m.
The walls of the excavation of depth in excess of 1 m (with the exception of excavations in compact rock) are secured be means of:
  • Producing the excavation with inclined (escarpment) walls
  • Installation of reinforcements to the vertical walls

Excavations with escarpments are produced in order to secure the walls against subsidence.  The gradient of the escarpment depends on the type of land, the atmospheric conditions and the duration fore which the excavation is to remain.  It can be assumed that a safe gradient of the escarpment for land of medium cohesion is approximately 45°.  Sandy soil embankments should have a gradient of no greater than the angle of the incline of the natural slope.
Excavations with vertical walls must have reinforcements of walls through expansion and support.  The type of reinforcement used depends on the size of the excavation, the type of land and the duration for which the excavation must remain.  The reinforcement of the walls to a depth of 4 m is installed as typical reinforcements on condition that no loading is anticipated in the immediate vicinity caused by structures, means of transport, stored materials, excavated materials, etc.
Excavations greater than this depth or the lack of adherence to the above conditions in securing the excavations should be specified in the technical documentation.
Furthermore, the following requirements should be observed:
  • An incline should be produced in the strip of land adjacent to the upper edge of the escarpment, at a width of three times the depth of the excavation enabling rainwater to be directed away from the excavation
  • The escarpments and the lining should be checked after every rainfall and after a long break in work, as well as every time before starting work
  • Changes in the structure of escarpment land as a result of the movement of this land should be liquidated while maintaining a safe slope to produce a safe entrance and exit into and out of the excavations
  • Construction materials and excavated materials should not be stored less than 1 m from the edge of the excavation, if the walls are lined; in the case of non-reinforced slopes, it is permissible to store materials beyond the soil wedge
  • Safe distances must be maintained between the excavations and existing buildings
  • The state of the lining or the escarpments must be inspected each time before works start in the excavation.
When excavating with the use of mechanical equipment, the danger zone related to the work of these machines must be marked.  It is necessary to become familiar with the technical documentation of the earthworks before starting these works.
In small construction works, e.g. construction of a house, the documentation is limited to the technical design of the building and the topographical map, being the site development plan.
The contractor of the earthworks should familiarise himself with the map on which the whole of the utility supply network is marked, and with the decision on the building permission.
In the event of conducting building works in the neighbourhood of electrical, gas mains supplies etc., the safe distance should be defined for conducting the works - in consultation with the operator of these devices (e.g. the electricity company).
Works in excavations and quarries or a depth of greater than 2 m and earthworks conducted not using the open pit method must be performed by at least two people [29].

 

 
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Module of the STER System supporting selection of personal protective equipment

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