这是从流沙层里露出来的马鞍的尖部。
It was the tip of a saddle protruding from beneath a sand drift.
论文发表网-摘要：井巷工程中出现流沙层，会给井巷工程的挖掘工作造成一定的干扰，严重时甚至会导致安全事故。
Summary: quicksand layer appears in the sinking and driving engineering will give well engineering excavation work caused a certain degree of interference, which can even lead to security incidents.
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