Macadam type bases involving successive layers of crushed rock bound with rock dust were also used.

人们曾经使用“石结”基层——几层由石粉黏结在一起连续的碎石层.

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For example, it required payment for workers with black lung disease from coal and rock dust.

比如说, 他要求矿主为工人提供因为灰尘导致的黑肺病的治疗.

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