Step 4 - Making the foundations - Laying the steel for the foundations

Phew our soil passed our plate load tests with flying colours.... onto stage 4.



Once the soil has been compacted and the tests have been done, we cover the bare soil with a thin layer of concrete to stop it getting wet and soggy as this would weaken the soils ability to take the pressure of the building.







The foundation is made up of around  1440 tons of steel reinforcing bar (Rebar) which is twisted and shaped into boxes. (using our earlier elephant analogy that 288 big ones..)

The rebar has different names depending on its diameter. For this foundation we use 7 types of rebar

R6 - 6mm round Bar - mild Steel
T10, 13, 16, 20, 25, 32 - which is t for torsional and the diameter of the bar in MM.

You can see the steel rebar being laid out to form a grid, and if you look closely you can see were we put more rebar at the column positions, to prevent the columns "punching" through the foundation (the punching shear). The punching shear of these these columns positions is around 600 tons of pressure...most of our columns will be around 1m x 1m in diameter.

Laying the first layer of rebar, its a very unpleasant job under the sun all day!

The final project - A complete mesh (not mess) of steel, like a box, ready to have concrete poured into it...

Step 3 - Making the foundations - Testing the soil

well we finished Step 1 and step 2 and now we need to tackle

Step 3.......

Once we have excavated the soil down to the right level, it is time to do some more tests which will help us confirm the design of our raft foundation.

The test we do here is called a plate load test...

For this test we put a plate under load..... (you see its not that hard, is it?)

We choose around 10 areas around the site and then construct a series of pads, we place plates on the ground and then slowly in a series of cycles place the plates under increasing pressure using an hydraulic jack. We test these plates up to a pressure of 800 Kpa  (kilopascal) ... 80 tons to the ordinary man on the street.

This is 3 times the ultimate planned weight of the building on the ground





The plate itself is only 30cm x 30 cm  and this weight is the equivalent of around 16 full grown african elephants balancing on this single point...

I have heard a rumour that in the olden days, before the hydralic jack this service was an important source of revenue for circuses with elephants.

 Almost there,  80 tons of pressure.

For the test to pass we allow only a deflection of a maximum of 2.5 cm into the soil! If the soil fails the test, this area of the site will need to have this soil removed and a better quality of bearing material added in its place.








More detailed information on this process can be found here!

Step 2 - Excavation - Preparing the foundations

Preparing the foundations...Digging a hole....

In the last step we decided to build a raft foundation, a big "raft" of concrete that is going to support the building, the first step to this is to dig out the existing soil...

Part of this building is an extension of the current basement carpark which is semi - underground (at the very front it is a ground level).

The site excavation size is about 67m x 81m with the depth ranges from 2.55m to 5.95m ( at the tent plaza end)

 This means we need to excavate about 16500 m3 of earth to get down to the start of the level of the foundations.

Each big earth moving truck that you see in Singapore can carry between 6 - 9 m3 of earth, depending on how well the earth is compacted when it is dropped in by the excavator.

So this means we need to remove around 2532 individual truck loads of soil from the site.......

Our soil goes to an earth dumping ground at Marina South and might be used for reclaiming more land around Singapore..More information on earth dumping in Singapore




Once the soil is removed and we have got to the final level that will form the foundations, we then compact the ground with 10,000 Kg vibrating roller. You can feel everything shake when this is working...