Hello Aneesh,

Happy New Year!!!!

Just some thoughts to share with you.... First of all your building is a "light" one so from my experience footing pressures should be around 70-100 kPa. The SPT values are quite low especially in the critical zone of influence below the footings. 2 things will control the foundation type for your structure, bearing capacity and settlements. Please also bear in mind that in case of footings, foundation level should be below 1.20- 1.50 m free surface so in this case you could suggest an excavation of 2 meters in order to reach the sand layers but again at 4m and 5m I see extremely low N values. How did you obtain the mechanical parameters?

So, first check your bearing capacity and then estimate settlements. Check this for single footings or strip footings (I am personally in favor of single footings with strong interconnection beams for small structures) and if any of the calculations does not meet your design criteria then you should consider other foundation types e.g. piles or footings with micropiles although your investigation depth (always in my opinion) is not deep enough

Regards

Hello Johnnix,

Thanks a lot for your inputs.

As I mentioned earlier I dont have any technical knowledge in soil mechanics. I can see from the soil test reports that the shear parameters (CKg/cm2 and Phy Degree) are calculated using the following methode

at 1 meter depth : Triaxial method is used to calculate the parameters.

at 3 meter depth: Direct Shear methode is used to calculate the parameters

at 6 m depth:Direct Shear methode is used to calculate the parameters

at 9 meter depth: Triaxial method is used to calculate the parameters.

I also noticed that there are three two storied houses which are almost 30 meters, 40 meters and 120 meters away from my proposed house site. All of these structures were made on footing foundation and there are no issues for these houses (all are new houses neary 2 to 3 years old). So can I assume that the soil profile is almost similar for these house then I can also go for footing design?

I have only the values reported in my first posting. Is it possible for me to calculate the bearing capacisty and settlements from these numbers?

Once gain your support is highly appreciated. Thank you and have a very nice day.

Aneesh

 

Hello Aneesh, You may perform the calculations you need but you will need to estimate Young's modulus from the SPT data you have as I cannot see any oedometer tests performed on your cohesive samples. Previous experience of your site from nearby structures is a good sign although in our profession 30 meters is a quite large distance! You could search for additional site investigation data from the nearby houses and see how they correlate with your profile. Regards

Thanks again. As you suggested, I will check the soil profile from near by locations. I also have a plan to reduce the dead weight. I am planning to use the rapid wall (made of Gypsm)

http://www.rapidwall.com.au/

By doing this, I can achive less pressure on foundation and may be only a low foundation will support the two storied house. Best regards aneesh 

It is very important to have proper drainage behind the wall as it is critical to the performance of retaining walls. Drainage materials will reduce or eliminate the hydrostatic pressure and will therefore greatly improve the stability of the material behind the wall, assuming that this is not a retaining wall for water.