Which risk increases when undermining a Roman fort's curtain wall reaches the talus?

💡 Explanation

When undermining reaches the talus, structural instability occurs because the talus provides sloping support to the foundation, so it weakens ability of the wall to withstand direct pressure from above and external forces. Therefore, premature wall collapse results , rather than catapult vulnerability, support removal difficulty, or flooding issues which arise from separate undermining factors or counter-measures.

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