During a siege, risk to tunnel stability increases significantly when which mechanism occurs?

💡 Explanation

Soil liquefaction increases the risk because it eliminates grain-to-grain contact, allowing the sandy tunnel walls to suddenly flow like liquid, therefore quickly leading to tunnel collapse, rather than soil consolidating, as a result of the intense localized vibration during siege weapon bombardment.

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• Which risk increases when unslaked lime is used in Roman mortar recipe during hydraulic concrete production?