02c. Model Soil Properties with Soil Calculator and Underground Piping in AutoPIPE

Attention: Please see the following AutoPIPE help sections:

Help > Contents> Contents Tab>

1. Reference Information> Pipe Soil

This section will provide information on

a. Model Discretization

b. Defining Soil Points in AutoPIPE

c. Soil Restraint Properties in AutoPIPE

d. Calculation of Soil Restraint Properties - AutoPIPE Method

e. Calculation of Soil Restraint Properties - ASCE Method

f. Calculation of Soil Restraint Properties - PRCI Method

g. Comparison of Soil Restraint Properties

h. Soil overburden stresses application on AutoPIPE points

 2. Modeling Approaches> Example systems> PIPE-SOIL Interaction: Transition Example.

The purpose of the following example system is to demonstrate the procedure required to

a. Calculate soil properties using AutoPIPE and ASCE method

b. Verification of values with hand calculations

c. Determine the location of critical piping points to be defined for the above to below ground (transition) piping system shown in the Figure below.

In this example, the piping system is subjected to a temperature rise of 230°F, and an internal pressure of 100 psi. For simplicity, a single soil will be assumed to interface with the pipe over the entire length of the buried portion of the system.

This online help section will provide step by step procedure of modeling soil properties in AutoPIPE.

3. Procedure described in AutoPIPE Workbook was developed by SSD for piping systems and pipelines who also help write ASCE “Guidelines for the design of buried steel pipe”.

4. Soil parameters Definitions

k1 – soil stiffness value at yield displacement of the soil (lb/in/ft) –  notice as this value decreases, the Yield Displacement will increase – Yield Disp. = p1 / k1

p1 – maximum soil resistance per unit length of pipe

k2 – stiffness of soil after yield has occurred (conservative to assume a small value)

Comments, Questions, and Answers about Soil Properties, Soil Calculator, and Underground Piping:

A. Pipe Soil Calculator issues:

1: Yield displacement value

2: Difference between AutoPIPE and hand calculations related to Qu term (vertical up) for sand, why?

3: In the Virtual Anchor Length equation, can the value for Co be adjusted?

4: Define soil properties after the node point La (i.e., in Zone 3)?

5: "Outside diameter" and "Depth to Center-line" affect on soil properties calculation when method = User

6: Calculate slippage length and virtual anchor length

7: Account for the weight of the soil acting down on the pipe

8: Calculate soil properties for a buried pipe on a 45 deg angled slope

B. Soil Over Burden issues & Buried Pipe Result Options:


1. These dialogs are only available for the following piping code years:

a. B31.1-2004 or higher
b. ASME B31.4 Liquid Trans. 2004 or higher when ASME CC N-755-1 (HDPE) option was enabled.
c. ASME B31.8 Gas Trans. & Dist 2004 or higher when ASME CC N-755-1 (HDPE) option was enabled.
d. ASME NC 2004 or higher
d. ASME NC 2004 or higher .

2. See AutoPIPE help for reference to Adams et. al.

1: Soil Overburden and Seismic Wave Propagation in AutoPIPE

2: Soil Overburden : dialog does not retain the entered inputs for the Soil Overburden Categories, why?

C. General Soil / Pipe issues:

1:  Fault line crossings

2: Long underground pipeline with traffic loading and large radius bend

3: Horizontal buried piping going under roadways / railways

4: Vertical Air Shafts or large diameter vertical underground piping

5: Node point on segment with soil settlement already defined make a big difference in the results

6: Alternative of performing buried piping analysis by using DeltaT equivalent

7: Determine pipe length needed for underground design

8: Stress on pulling a pipe into a directional drilled hole

9: Little more weight the results increase exponentially to become severally over-stressed, why?

10: Fully restrained piping, does the program make the necessary corrections for this condition?

11: Underground piping above / below the frost line

D. Seismic Wave Data issues:

1: Seismic Wave Data reference for default values

See Also

Modeling Approaches

Bentley AutoPIPE