TOP CITY , WATTALA, SRI LANKA

Two Storied house in 8 perch land plot.

foundations:
According to the outcome of the soil test , Structural engineer advised to construct 12 Nos. Column bases from the steady sandy soil layer which found 12 feet from the existing ground level.
According to his advice, and close supervision by our technical staff, the excavation was done up to Fourteen feet from the existing ground level.
Down to 6 feet depth filled laterite soil found and water could found at 5 feet level, but it rise up to 3 feet level with the time.
at 6 feet level, thin layer of yellowish grass residues could found and from that level to 12 feet level black colour peat was there.
the peat layer is without water, hence some what easy to excavate. 
had to do shoring to avoid filled loosed soil comes with the water and used 2" sub-immersible electric pump for de-watering.
In almost all pits, we found tree logs or huge roots. most of the could cut and remove with the use of a axe. But in four cases we had to use electric chain saw to cut those and had to spend a whole day for that. In one case the Log was so huge and harden, we have to shift the column position, with the advice by the structural engineer.
At the 12 feet level, coarse sandy soil very similar to River sand was found with several, unstoppable water fountains, we had to use 2 Nos. 2" 1.5 HP sub-immersible water pumps for de-watering.
at the 14 feet level while doing de-watering ,our team could make a tank like area in the form work , using 1000 Gage thick polyethylene, and put the base, while de-watering.

this could prevent water come in to the base concreting, and had to keep the pumps running over night . According to the Structural engineers recommendations, we put 2'-6" X 2'-6" X 9" Column bases using Grade 25 concrete mixture and 10 No. 10mm SLS Certified Tor steel. On these bases, 10" X 10" columns using grade 25 concrete and 4 Nos. 12mm SLS certified Toe steel with stirrups at 8" intervals we constructed using steel form work. This was done under close supervision of our technical staff.