This shift is due to both improved safety standards and technology as well a move away from underground mines towards surface mining and controversial mountaintop-removal mining.
这种数据上的提高在于安全标准的提升和技术的进步，同时，地表开采和富有争议性的削山开采也使得地下开采也逐渐走到地上。
The roof shape optimization is one of the important means to control the ground pressure. A long strip of exposed roof surface shape can improve productivity of the stope and ensure mining safety.
优化采场顶板暴露面积形状是控制地压的重要手段之一，采用长条形顶板暴露面，能提高采场生产能力和保证回采的安全性。
It is the most common way to remain coal safety pillar for protecting surface buildings from mining damage.
留设保护煤柱是防止建筑物受采动损坏的最常用方法。
It is the most common way to remain coal safety pillar for protecting surface buildings from mining damage.
留设保护煤柱是防止建筑物受采动损坏的最常用方法。
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