This application allows the user to calculate percent deflection in buried flexible pipe utilizing the Modified Iowa Equation:

Where, % ∆Y/D = % pipe deflection, dimensionless

This equation has been used since the late 1950’s to accurately calculate expected maximum deflections. The application allows the user to choose each of the input variables based upon specific known conditions and also offers the option of selecting inputs from recommended values.

Parameters

Deflection Lag Factor:

DL = Deflection lag factor, dimensionless; Use 1.0 when using prism load for dead load calculation.

Bedding Angle Constant, K
0.110
30° 0.108
60° 0.103
Recommended 0.100
90° 0.096
120° 0.089
150° 0.085
180° 0.083
Your Value

K = bedding constant, dimensionless; 0.1 is generally accepted as a conservative value.


400,000 modulus

500,000 modulus

Enter Custom Value:

PS = pipe stiffness, psi

Soil Modulus:
Soil Class E' for Degree of Compaction of Bedding, in psi
Dum-ped Slight, <85% Proctor, <40% relative density Mod. 85% - 95% Proctor, 40% - 70% relative density High, >95% Proctor, >70% relative density
Crushed Rock 1000 3000 3000 3000
Sand and Gravel (no fines) 200 1000 2000 3000
Sand and Gravel (with fines) 100 400 1000 2000
Fine Grained Soils 50 200 400 1000

E’ = modulus of soil reaction, psi

Add. Live Load:
No Live Load
Single-Wheel Load
Two Passing Trucks
H20 Highway
E80 Railway
Airport
Max Wheel Load (lbs)
Pipe Diameter (in.)

W’ = live load, psi

lbs/Ft3 κμ Material
100 0.1650 Dry Sand
115 0.1650 Ordinary (damp) Sand
120 0.1650 Wet Sand
120 0.1300 Damp Clay
130 0.1100 Saturated Clay
115 0.1500 Saturated Topsoil
100 0.1650 Sand & Damp Topsoil
105 0.1924 Granular Materials Without Cohesion
Your Value

P = vertical soil pressure due to the prism load, psi.

The prism load represents the maximum soil load on flexible pipe.

Depth of Burial:
Start End Increment

Results