Check the fluctuation of mud level whenever 20 strings pulled out.

每起钻20柱，要核对泥浆的升降情况。

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Freezing mud that reached track level could derail a train, and rock salt kept the mud soft.

铁轨周围结冰的泥土会造成火车脱轨，岩盐可以使泥土保持松软。

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The level of mud liquid goes up or down as its temperature changes.

泥浆液面随温度的变化而升降。

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The obstacles increase at each level and can involve water, mud, hills, walls, fire, even learning Greek and answering riddles.

FORBES: Spartan Racing Series Drawing Huge Numbers, Clearing All Obstacles