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Assalam O Alykum I want opinion from seniors on the following 1. I am working on raft pile cap and piles will be designed by company name swiss boring most probably. If I reduced the stiffness of of raft pile cap to 0.25 and compare that reaction value with the pile capacity is it good approach what do you suggest. Its over conservative I know, but the problem is that geotechnical specialist who gave the values of pile capacity etc. not having good reputation. 2. Any code that recommends the safe boring distance between piles. Apologise small addition, I also ignore the subgrade reaction under the pile raft and consider 7500 Kilonewton per meter cube. However, in geo tech report it's mentioned 20,000. Thank you

Hi All, I'm trying to model the behaviour of pile-raft (250mm thk. slab and 300mm dia. piles) supporting a 1-storey building with the piles modelled as spring support. The software I'm using is ROBOT structural analysis. After running the analysis, as you would expect, the support at the centre where the loads are at its highest gives a larger reaction than the ones on the edge. Once I reduce the spring constant value, the reactions still exhibits a similar behaviour, however I realized that now the loads redistributes itself in a way that the support receiving higher loads at the centre are now giving a lower reaction (as compared to the case with larger spring constant value), and the edge supports are giving a higher reaction (as compared to the case with larger spring constant value). I have also created various other models as experiments, and it seems to be giving the same trend. It's almost like the loads try to ''even out'' itself everytime I reduced the spring constant value. So I'm just wondering, is this the sort of behaviour we should be expecting from a geotechnical point of view? From what I understand, the load distribution should be the same if the spring constant value for all supports are the same as the stiffness are all equal. And regardless of what value of spring constant you use, the sum of reactions should be the same. Replies will be much appreciated, many thanks in advance.

Dear Seniors! I designed a shallow raft foundation but it seems to be unstable due to low SBC. Therefore, I decided to design a deep foundation (Piles beneath the Raft). Can somebody tell me how to design a deep foundation that is Piles+Raft in ETABS. I need urgent help, please.