Buried Plastic Pipe Wall Crushing Equations Formulas Design Calculator Pressure

Fluid Mechanics Hydraulics

Problem:

Solve for pressure on pipe.

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Solution:

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wall crushing - pressure on pipe

	pressure on pipe
	pressure due to soil weight
	pressure due to wheel load
	internal vacuum pressure

wall crushing - thrust in pipe wall

thrust in pipe wall

wall crushing - required wall cross sectional area

	required wall cross sectional area
	thrust in pipe wall
	allowable long term compressive stress

References - Books:

National Resources Conservation Service. National Engineering Handbook. 1995. United States Department of Agriculture.

Background

Engineers must consider various forces acting on the pipe when designing underground plastic pipelines, such as soil weight, traffic loads, and internal vacuum pressures. Understanding these pressures ensures the pipe's integrity and longevity. These equations were developed based on extensive research documented in the USDA's National Engineering Handbook.

Equation

The fundamental equation for determining the pressure on a buried plastic pipe is:

P = PS + PW + PV

where:

P is the pressure on the pipe.
PS is the pressure due to soil weight.
PW is the pressure due to wheel load.
PV is the internal vacuum pressure.

How to Solve

Identify Inputs:

Pressure Due to Soil Weight (PS): This pressure comes from the weight of the soil above the pipe.

Pressure Due to Wheel Load (PW): This pressure arises from traffic or other surface loads.

Internal Vacuum Pressure (PV): This internal pressure is within the pipe, usually due to fluid dynamics or vacuum.

Convert Units:

Ensure all pressures are in the same unit system for accurate computation (e.g., Pascal, pound per square feet).

Apply the Equation:

Substitute the identified pressures into the equation: P = PS + PW + PV.

Compute the Result:

Solve for P to determine the total pressure exerted on the pipe.

Example

Let's consider an example to illustrate the application of this equation:

Pressure due to Soil Weight (PS): 2000 pounds per square foot (lb/ft²)

Pressure due to Wheel Load (PW): 500 pounds per square foot (lb/ft²)

Internal Vacuum Pressure (PV): 300 pounds per square foot (lb/ft²)

Using the equation:

P = PS + PW + PV

P = 2000 + 500 + 300

P = 2800 lb/ft²

Thus, the total pressure on the pipe is 2800 pounds per square foot.

Fields/Degrees it is Used In

Civil Engineering: For designing and evaluating buried infrastructure.
Environmental Engineering: Ensuring water and waste management pipelines can withstand external pressures.
Mechanical Engineering: Understanding mechanical stresses on buried pipelines.
Geotechnical Engineering: Studying soil-pipeline interaction.
Chemical Engineering: Pressure integrity is crucial for pipelines transporting chemicals.

Real-life Applications

Water Distribution Systems: Designing pipelines to transport water under roads and ground.
Sewage Systems: Ensuring sewer pipes can withstand soil and traffic loads.
Gas Pipelines: Calculating pressures in buried gas transport pipelines to prevent leaks.
Telecom Ducts: Protecting fiber optic cables laid underground from physical damage.
Irrigation Channels: Ensuring durable piping systems in agricultural fields.

Common Mistakes

Ignoring Unit Consistency: Failing to convert all pressures into the same unit system.
Overlooking Traffic Loads: Not considering external pressures from surface loads.
Incorrect Soil Pressure Calculations: Misjudging the soil's weight and its distribution.
Underestimating Vacuum Pressures: Neglecting the impact of internal vacuum pressures.
Wrong Pipe Material Assumptions: Using equations suitable for plastic pipes on non-plastic materials.

Frequently Asked Questions

Q: What is the primary purpose of the buried plastic pipe wall crushing equations?
A: These equations help compute the total pressure on buried plastic pipes, ensuring they can withstand external loads and internal pressures.
Q: How do you convert between different pressure units when using these equations?
A: Utilize pressure conversion tools or equations to ensure all pressures are in the same measurement unit before solving.
Q: Can these equations be used for materials other than plastic?
A: No, these specific equations are optimized for plastic pipes and may not provide accurate results for other materials.
Q: Why is it essential to consider wheel load pressure (PW) in the calculations?
A: Wheel load pressure accounts for external forces from traffic or heavy vehicles impacting the pipe, which is crucial for accurate pressure analysis.
Q: Where can I find the reference material for these equations?
A: The primary source is the USDA's National Engineering Handbook (1995), which provides detailed insights and guidelines.