I have a plan area for constructing 1

[Maher8880]

I have a plan area for constructing a 20 storied building . In the plan area there are some problems with the soil. At one point there is hard rock layer nearer to the ground suppose 5-10m. So pile foundation can't be constructed, may be mat or raft foundation can be constructed. On the other end, there is loose soil in the deeper to the ground , so pile foundation should be constructed. but this will cause differential settlement. I can make underground basement, using shore piles at the boundary line. How to design the building? what is the solution?

 

[driftLimiter]

20 stories? A rigorous geotechnical / structural engineering effort by qualified individuals. Please consider the repercussions of such a design failing. This is not a problem left to anonymous individuals on a web forum.

 

[Maher8880]

Can you suggest some ideas?

 

[rb1957]

this is a school project, yes? The only one hurt by failure is the OP (yes, heartless aren't we).

This sounds to me to be a complicated situation (as one might expect in a school project) where there are probably several acceptable approaches/solutions (and no doubt several unacceptable ones too).
If a school project, then the point is to demonstrate how much you've learnt. And clearly you have learnt something, you seem to talk about some of the problem elements, and the things they impact in the solution, and the problems that arise. Ok, keep going ... how would you avoid/mitigate/minimise differential settlement (if part of the building is supported on piles to solid rock) ?

"Hoffen wir mal, dass alles gut geht !"
General Paulus, Nov 1942, outside Stalingrad after the launch of Operation Uranus.

 

[driftLimiter]

Fair enough this is the student forum.

With little information about the shpe of the building relative to the described soil profile it is difficult to provide much but in general...

Perhaps A large single mat foundation / pile cap could be designed to mitigate differential settlement.

If the structure is large enough in plan consider a seismic joint to separate the building into two that are each founded upon one soil type.

 

[BridgeSmith]

Why would dismiss a pile foundation due to shallow depth of rock under some parts of the building? This is where driven pile foundations shine. You drive all the piles to refusal, whether short or long, and you get consistent support across the entire foundation.

If you're not getting enough lateral stability from vertical piles, due to inadequate embedment, consider predrilling the rock or having some battered (driven at an angle) piles.