Cohesive

The following properties are required or available for cohesive soil layers:

• Reduction Factors (%) – percent decrease in computed unit resistance for layer
  • Skin Resistance Loss
  • End Bearing Loss
• Unit Resistance Limits – maximum value of unit resistance
  • Skin Friction Limit
  • End Bearing Limit

Note that the skin friction resistance is capped by 5% of the entered Concrete Cylinder Strength in the pile properties.

The following parameters are required for each method as described below. For more information see Bored Capacity Theory Manual.

Total Stress Calculations – Alpha Method

Skin Friction and End Bearing Parameters:

• Undrained Shear Strength, Su

Skin Friction Parameters:

• Alpha (α)

The ultimate unit skin (frictional) resistance (f_s,ult) is computed as follows:

f_s,ult =α Su

End Bearing Parameters:

• Bearing Capacity Factor Nc

The ultimate unit end (base) resistance (q_b,ult) is computed as follows:

q_b,ult = Nc Su

Effective Stress Calculations – Beta Method

Skin Friction Parameters:

• Beta (β)

The ultimate unit skin (frictional) resistance (f_s,ult) is computed as follows:

Where:

End Bearing Parameters:

• Effective Cohesion, c’
• Bearing Capacity Factor Nc
• Bearing Capacity Factor Nq

The ultimate unit end (base) resistance (q_b,ult) is computed as follows:

Where: