Pile Load Capacity Calculation Using Static Cone Penetration (SCPT) Test Data
The safe load capacity of bore cast in situ piles can be calculated using test data obtained from Static Cone Penetration Test as described below.
We know that the final load capacity of a pile consists of two terms, namely
- end bearing resistance
- skin abrasion resistance
So we need to calculate the above two parameters, then by adding these two parameters we can get the final load capacity of the pile.
Step-1 (Calculate the end-bearing resistance of the pile)
The final end bearing resistance of the pile is calculated using the formula below.
WhyYou = final end bearing resistance, kN/m . In2
Whyc0 = kN/m . Average static cone resistance at a depth of 2d below the pile tip in2
WhyC1 = kN/m . Minimum static cone resistance at the same 2D below the pile tip in2
Whyc2 = in kN/m, the average of the envelope of minimum constant cone resistance values over a pile length of 8D above the pile tip2
d = diameter of the pile
Step-2 (Calculate Skin-Abrasion Resistance)
For a variety of soils, the ultimate skin abrasion resistance (f.)s), kN/m. In2, can be obtained using the table below.
|soil type||Skin abrasion resistance (fs), kN/m . In2|
|WhyC 1000 kN/m . less than2||WhyC/30 to QC/10|
|Soil||WhyC/25 to 2qC/25|
|silty sand and silty clay||WhyC/100 to QC/25|
|Sand||WhyC/100 to QC/50|
|coarse sand and gravel||WhyC/150 to QC/100|
where, whyC kN/m . has cone resistance2,
Step-3 (Calculate Safe Heap Load Capacity)
Add end end bearing resistance (QYou) and ultimate skin abrasion resistance (f.)s) as calculated in step-1 and 2 respectively, and divide it by the appropriate factor of safety (minimum 2.5) to obtain the safe load capacity of the pile, i.e.
WhySafe = (QYou+fs) / FOS
WhySafe = safe load capacity of the pile
WhyYou = End end bearing resistance of pile
Fs = final skin abrasion resistance of the pile
FOS = heap protection factor (usually 2.5)