Question

You are responsible for the construction of a medium sized inner city building. The foundation material consists of hard, high quality shale overlain by three metres of clay and a metre of top soil. The site has a street at the front and the rear. Buildings adjoin the other sides of the property. These buildings do not have below ground levels, the basement slab is located just half a metre below the surface. Both buildings have pier fotings down to rock and they will not require underpinning. You first task is to prepare the site for structural foundation work by excavating to a level three metres below the rock surface. In your exam booklet write a task statenment for completing the work, list the equipment and techniques that you would use, explain the various reasons for your choices

Answer 1

In the given question, we can clearly say that both buildings have pier footings down to the rock. And there will be no requirement of underplanning. We can complete the task in the following manner.

1.Generally, there are many tools available for excavation of shallow depths. Those are mainly spade, shovel, hoe, trowel and rack etc. These are called hand tools.

2.When coming to the large depths, we can use bulldozers, wheeled excavators, drag line excavators and backhoe excavators. These are called machinery equipment.

3.Initially, we should excavate upto 3 mts. by using one of the machinery equipment which is mentioned in (point 2) .

4.Since the given building area is some how large, it's better to choose the mechinery equipment for excavation. Clean the site to make a proper work. We should remove the waste papers, stones and unnecessary things. Then, the surface should be leveled completely.

5.After that,an equipment called percussion driller is used to make the required holes in the soil strata. This equipment is simply suitable for the given soil type.

6.We have to provide the different type of piers as per the requirements.

7.Mostly, rcc piers can be preferred for the normal buildings.

8.We should provide the proper spacing between each piers by measuring with a metallic tape.

9.This is the main this we've to consider, because we can't change later once we started the work.

10.If we choose helical foundation,then sonotubes can be used at the work of installation of piers.

11.Sonotubes are the metallic spiral duct. We should apply the oil to the inner surface of the sonotube.

12.After digging hole. We should construct the individual footings first. Longitudinal bars also should be extended up to the ground level.

13.Then, we should place the sonotubes which consists the height up to the ground surface.

14.Make the proper concrete mix by using concrete and stone crushers,concrete mixtures or ready mix concrete trucks. Pour the concrete in that hole completely.

15.Then, remove the sonotubes.Now, the piers are at the ground level. Then, provide the longitudinal and transverse reinforcement and make the beams and slab which connects all the piers. This is the one of the best methods to prepare the site for structural foundation work. The type of installation varies from place to place.