Holdfast Training Services Trial Blog

On the Paradise Circus site there are a number of different types of foundations:

1. Rotary bored piles (900mm and 1200mm)
   1. Single pile caps
   2. Grouped pile caps
   3. Cantilevered pile caps with tension piles
2. Ground beams
3. Pad foundations
4. Ground bearing slabs
5. Suspended slabs

The last two are pushing it, but I thought I would throw them in as they are definitely in the future of this project.

I have been asked to investigate a request by the designer that the location of the Pad foundations be subject to a Plate Bearing test (Carillion are obsessed with these and so seems the industry as a whole – has anyone else experienced this?). The plate bearing test has been specified as a must have to us and due to my protests at this, I was given the task of liaising with the designer.

The need for this test is to qualify the assumptions made during design – happy with that. The test must be completed at the formation level of the pad foundation – not happy with that.

Although the pad foundations are nominally 1.2m deep, the formation level is the Sandstone strata that at it’s highest point is about 3.5m BGL. In order to conduct a plate bearing test there needs to be a technician with the equipment and a machine large enough to create the pressure needed on the plate.

Edit: The distance between the bottom of the pad foundation and the rock strata is made up with mass concrete fill (bonkers?)

I conducted a similar test on a 450mm dia plate at 550kPa and needed a 22T machine to Jack-off – this test has been specified to 1500kPa. Here is a photo of the former.

Take in  to account the excavation to 3.5m depth and a safe batter of 1:1.5 (Carillion standard for large excavations) and the requirement to do about 10 of these over the site – we’re looking at basically doing a reduced level dig to the sandstone across the site.

Now I have asked the question “What do you want to know, Mr Designer?” As I said previously, the aim is to qualify the assumptions made during design – these are regarding settlement. The designer has come back at me with “Stiffness”.

I now need a method of finding the stiffness of the sandstone between 3.5 – 10m depth across the site – without excavating enough material to fill Wembley stadium. I have made some suggestions but will keep these to myself for now – what would you have said or come up with?

I am responsible for the fitting out of a basement area and so I am trying to sequence the works, using the BIM model to decide the order in which stuff needs to be installed.  As such my works programme is becoming pretty complex.   Here is a 3D BIM model of the area I have to fit out including all pipework, ladder racks, trays, ductwork and basketry.  This task will involve the management of six separate sub-contractors and their interfaces.

BIM is a great tool but very slow and I am finding that the constraint on when I can start each work package is not the supply of materials or availability of sub-contractors but rather the production of construction drawings.  So now we are at the point where the drawing production programme is driving and dictating the MEP programme.  Due to a lack of coordination at the start of drawing production, the drawings are not being produced in the sequence of construction, causing further delays in several areas and messing with my programme.  We have now coordinated with the BIM Team and created a drawing sequence that better reflects what we plan to do on site.

Is this issue unique to our site or common place where BIM is the primary driver of the Building design?

Here is another pic of the basement area showing the complexity of the task:

Sadly, I will not be able to finish the fit out of this area before departing the project and so will not be able to install the whole of the ductwork, smoke extract system, fire alarm system and most of the cable racking.