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Difficulty: MediumDrawing Logical Conclusions

Read the passage about railway track engineering. Based on the provided facts, what term logically completes the concluding deduction?

Answer:Continuous welded rail (CWR) expands longitudinally as ambient temperatures rise. To prevent track buckling, maintenance crews anchor the steel rails at a calculated neutral temperature and reinforce them with compacted crushed-stone ballast, which provides lateral restraint against expansion forces. When routine maintenance disturbs the surrounding ballast during cool weather, the track's lateral resistance is significantly compromised. Consequently, if seasonal temperatures rise sharply before the ballast has fully reconsolidated, the expanding rails are under severe risk of 【buckling】.

Answer

buckling (or track buckling)
The text states that compacted ballast is necessary to supply the lateral restraint that prevents expanding rails from buckling. Because the passage specifies that the ballast was disturbed (reducing lateral resistance) and temperatures subsequently rose (increasing expansion), the direct and necessary logical deduction is that the track will experience buckling.

Step-by-Step Solution

1
Identify the cause of mechanical stress and the role of the safety mechanism.
Rising temperatures cause longitudinal expansion in the rail, which induces buckling unless compacted ballast provides sufficient lateral restraint.
Establishes the foundational relationship between thermal expansion and the structural support needed to keep the track aligned.
2
Evaluate the specific vulnerability introduced by the scenario.
Disturbing the ballast during maintenance removes the lateral resistance required to counteract expansion.
Identifies that the critical protective condition has been disabled before thermal expansion occurs.
3
Deduce the inevitable physical consequence when temperature increases.
With expansion forces active and lateral restraint compromised, the rails will buckle.
Synthesizes the active expanding force with the compromised restraint to reach the only supported conclusion.

Key Concept

Synthesizing cause-and-effect relationships and physical constraints in a technical passage to deduce a logical outcome.
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Drawing Logical Conclusions

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