₦airaland Forum

Good day nairalanders,

My soil test report just came out as shown below, can I build a story on this kind of land using conventional raft foundation?

The test suggest conventional raft or piling. Surely, I can't afford Pilling but I still have to be sure that raft is good.

 0 – 1.50m - Brown to reddish to rust brown silty, sandy clay.
 1.50 – 2.25m - Dull brown to dark grey stiff clay.
 2.25 – 3.75m - Dull brown to dark grey stiff clay with organic materials.
 3.75 – 9.75m - Dark grey soft clay.
 9.75 – 12.75m - light grey (fmc) soft sandy clay.
 12.75 – 18.75m - Brownish grey to dark grey silty stiff clay.
 18.75 – 30.00m -yellowish brown to brown fine medium to coarse
dense sand.
Groundwater was at a depth of 1.80m at the time of the investigation.

N-value for the sandfill as presently existing can be taken as 2.
Peck, Hanson and Thornburn have related standard penetration values (N), allowable
net bearing capacity, and settlement as follows in sands:
qa = Cw (0.41)NΔH
where qa = allowable net bearing capacity
N= 1 (from standard penetration test results)
ΔH = Settlement in mm (limiting settlement to 50mm)
Cw = water table correction factor (0.5)
qa = 0.5 × 0.41 ×2 × 50
= 20.5 KN/m2