Selection of stones for retaining walls — which property is most important for stability against earth pressure? Pick the most appropriate attribute.
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ASoft
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BHard
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CLight
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DHeavy
Answer
Correct Answer: Heavy
Explanation
Introduction / Context:Retaining walls resist lateral earth pressure through a combination of weight, geometry, and structural action. When using masonry or random rubble, the self-weight of the stones plays a critical role in preventing sliding and overturning.
Given Data / Assumptions:
- Traditional gravity or semi-gravity retaining wall using stone masonry.
- Primary concern is global stability under lateral soil loads.
- Material choices influence unit weight and durability.
Concept / Approach:For gravity action, higher unit weight provides larger stabilizing moments and frictional resistance. While hardness relates to durability and abrasion resistance, “heavy” directly targets the wall's self-weight, which is the main stabilizing factor against overturning and sliding in gravity-type walls.
Step-by-Step Solution:
1) Identify governing failure modes: overturning and sliding due to earth pressure.2) Stabilizing actions depend on wall weight and base friction; heavier stones increase both.3) Soft vs hard: Hardness affects wear and long-term durability but not weight-based stability as directly as density.4) Light stones reduce stabilizing weight and are undesirable for gravity walls.Verification / Alternative check:Design handbooks emphasize unit weight for gravity walls, often using dense stones or concrete to attain needed resisting moments.
Why Other Options Are Wrong:
- Soft: Suggests lower strength/durability; not preferred.
- Hard: Desirable for durability but secondary to unit weight for stability in this context.
- Light: Reduces self-weight; unfavorable.
Common Pitfalls:Equating surface hardness with structural stability; forgetting that gravity walls primarily rely on mass.
Final Answer:Heavy