Spontaneous combustion of a coal seam was mainly caused by oxygen in leaked air.

矿井煤层自燃主要是由于漏风供氧引起的。

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This seam of coal reposes on a layer of clay.

这个煤层处于一层黏土岩之上。

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The structural deformation is the principal geological factor that affects the thickness variation of coal seam on a mine field scale.

构造作用是控制井田范围内煤层厚度变化的主要地质因素。

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The drill also went through a coal seam at 660m that nobody knew existed.

BBC: Newcastle University borehole project strikes hot water

The concept of heating underground coal to a combustion point may lead one to recall Centralia, PA, an abandoned town in Pennsylvania sitting on a coal seam which has been burning for 50 years, but the UCG controlled process makes that outcome highly unlikely.

FORBES: Underground Coal Gasification: A Trend Worth Watching

Two more men escaped unaided from the drift mine - a mine cut into the side of a hill where the coal seam is accessed horizontally - before emergency services arrived.

BBC: Trapped miners: Bid to rescue men in Swansea Valley