Holdfast Training Services Trial Blog

It seems I do have time to add another blog.

As I have discussed in previous blog, the pile group for the buildings were next to a railway track. In order to excavate the ground next to the viaduct, a retaining wall was required. However the retaining wall could not be supported by props as there was nothing to prop against. A a result the retaining wall was supported by buttress’.

As you can see from the drawing above, the buttress’s are spaced by 13m and comprise of 4 x male piles and 3 x female piles. The spacing between the males are 1300mm. The original design allows for the  female buttress piles to be installed to the depth of the retaining wall piles, allowing the male ones to go deeper to provide the stability. I was interested to find out how they had designed the buttress wall toe depth for the male piles. Here is a quick sketch of the way I calculated the resistance of the buttress piles.

It seems to agree with Skanskas approach. However they had a toe depth of 11.6m, different to my 13m. I soon realised that they had made an error in their calcs, they had forgotten to work out the area of resistance correctly. Secondly I was concerned that if they were using L=4.65m, they should extend the length of the female piles to the same length as the male ones. The soil that is caught between the male-male piles would not create the same friction as male female pile combination. These factors have gone back to Skanska, I await their decision. I hope my suggestions are correct!