Weak Layer under mat foundations

Dear Friend,
I wonder if anybody has any openion on how to handle relatively thin weak layers encountered under the mat foundation in the shear wedge region. These type of layers are very weak (N<5) and compressible.
thanks a lot

 

[Sean2]

The information you provide is very limited. However, I will try to help, based on what you have provided.

Assess the load (and the resulting stress in the layer) and the tolerance of the structure to movement or to differential movement. It may be that the movement caused to your structure, taking a worst case combination of properties for the weak stratum, is well within tolerance.

Given that your soil is compressible as well as &quot;weak&quot;, and assuming that the settlement of your structure would be unacceptable, you either have to remove the material, replacing it with suitable material, or you have to treat the ground, or you have to pile the structure. The most appropriate ground treatment will depend on the nature of the weak layer and on the overlying ground.

I have used &quot;balanced foundations&quot; before for large structures, but the compressible strata were not at shallow depth.

I suggest you obtain direct specialist advice. If your structure is either populated or relatively large, the risk is too great for you to rely solely on advice obtained in this forum at a distance from your project.

 

[Focht3]

Ditto Sean2's advice.