Pressure conduit laid underground: which action is typically negligible? A pressure conduit (pressurized pipeline) installed below ground may be subjected to several actions. Which of the following it may generally not be subjected to in significant magnitude under normal design assumptions?

Introduction / Context:
Underground pressure conduits are designed for multiple actions, including internal hydraulic pressure, soil overburden, traffic loads, and forces from fittings. This question checks awareness of which action is generally negligible for buried lines: longitudinal temperature stress.

Given Data / Assumptions:

• Pipeline is buried below ground level.
• Normal civil engineering conditions (no extreme temperature cycling such as steam lines).
• Fittings (bends/tees) may create thrust that must be resisted.

Concept / Approach:
Temperature-induced axial strain in buried water pipelines is typically restrained by surrounding soil and, more importantly, daily/seasonal soil temperature variations at burial depth are small. In contrast, internal pressure, external loads, and unbalanced hydraulic thrusts are real and must be designed for.

Step-by-Step Solution:

Verification / Alternative check:
Design manuals for buried water mains emphasize pressure class, ring stiffness, and thrust restraint; temperature considerations focus on expansion joints primarily for above-ground runs.

Why Other Options Are Wrong:

• Internal pressure (a) is fundamental for pressure-class selection.
• External loads (b) drive ring buckling and wall stress checks.
• Unbalanced pressure at bends (d) requires thrust blocks/anchorage.
• “None of these” (e) is incorrect since (c) is the best answer.

Common Pitfalls:
Confusing above-ground pipelines (where thermal movement can be large) with buried lines; ignoring thrust at fittings; assuming soil load is negligible.

Final Answer:
Longitudinal temperature stress