Excavation Shoring
Shoring is a type of temporary prop or support that is used in the repair or construction of buildings, as well as in excavations. For example, temporary support may be needed to ease the weight on a masonry wall while it is being repaired or reinforced.
What is Shoring
Shoring is a type of temporary prop or support that is used in the repair or construction of buildings, as well as in excavations. For example, temporary support may be needed to ease the weight on a masonry wall while it is repaired or strengthened. Shoring the wall with large timbers sloping upward at around 65° to 75° can provide stability. The top of the wood is framed onto a base to transmit the weight to the ground with little distortion, while the lower end of the timber is framed onto a base to transfer the load to the ground with minimal deformation. Wedges can be employed to bring the coastline into close proximity to the wall. If the wall is many storeys tall, a vertical is the best option.
Type of Shoring.
1. Dead Shoring
This type of shoring is used to support dead loads that act vertically downwards. In its simplest form, it consists of a vertical prop or shore leg with a head plate, sole-plate, and some means of adjustment for tightening and easing the shore.
1. Carry out a thorough site investigation to determine.
- A number of shores required by ascertaining possible loadings and window positions.
- Bearing capacity of soil and floors.
- Location of underground services that may have to be avoided or bridged.
2. Fix ceiling struts between the suitable head and sole plates to relieve the wall of floor and roof loads. The struts should be positioned as close to the wall as practicable.
3. Strut all window openings within the vicinity of the shores to prevent movement or distortion of the opening.
The usual method is to place timber plates against the external reveals and strut between them; in some cases, it may be necessary to remove the window frame to provide sufficient bearing surface for the plates.
4. Cut holes through the wall slightly larger in size than the needles.
5. Cut holes through ceilings and floors for the shore legs.
6. Position and level sleepers on a firm base, removing pavings if necessary.
7. Erect, wedge, and secure shoring arrangements.
Upon completion of the builder’s work, it is advisable to leave the shoring in position for at least seven days before easing the supports, to ensure the new work has gained sufficient strength to be self-supporting.
2. Raking Shoring
This shoring arrangement transfers the floor and wall loads to the ground by means of sloping struts or rakers. It is very important that the rakers are positioned correctly so that they are capable of receiving maximum wall and floor loads.
The operational sequence for erecting raking shoring is as follows:
- Carry out site investigation as described for dead shoring.
- Mark out and cut mortises and housings on a wall plate.
- Set out and cut holes for needles in an external wall.
- Excavate to a firm bearing subsoil and lay grillage platform and sole-plate.
- Cut and erect rakers, commencing with the bottom shore. A notch is cut in the heel so that a crowbar can be used to lever the raker down the sole-plate and thus tighten the shore (see below figure). The angle between sole-plate and shores should be at its maximum about 89° to ensure that the tangent point is never reached and not so acute that levering is impracticable.
- Fix cleats, distance blocks, binding, and, if necessary, cross-bracing over the backs of the shores.
3. Flying Shoring
These shores fulfill the same functions as a raking shore but have the advantage of providing a clear working space under the shoring.
They can be used between any parallel wall surfaces provided the span is not in excess of 12.000 m when the arrangement would become uneconomic.
