One of the major concerns for longw

One of the major concerns for longwall mining is the extent of surface subsidence and its
induced surface structural damages. The experiences have been that room and pillar reining with
low recovery, eg, no pillar mining can be implemented such that no measurable surface
subsidence occurs during the period of underground mining, although subsidence may occur Long
after ( say 40~50 years)mining. In contrast, the general concept about longwall mining is that
since there is a complete extraction of coal in a longwall panel, there will be much larger surface
subsidence and thus structural damages. This is to same extent justifiable because past research
has demonstrated that surface subsidence due to longwall mining occurred even when the seam
Depth was close to 1000 ft .and that minor crackings could occur in a residential house depending
on the type and location of the residential house within the panel.In other words under longwall
mining there could be some damage to some surface structures such as houses. But it can be
protected such that the damages are so minor that except minor crackings, the houses are
practically the same before and after mining.

結果 (中文) 3:

一种长壁开采的主要问题是地表沉陷的程度及其
诱导的表面结构的损伤。的经验，房柱式控制与
回收率低，例如，可以实现无煤柱开采，地下开采过程中发生不可测量的表面
塌陷发生，虽然长
后可能下沉（40 ~ 50年）挖掘。相比之下，对长壁采煤法的一般概念是
既然是一个完整的提取在工作面煤，将有更大的表面
沉降，结构损伤。这是因为过去的研究同样程度的正当
表明地表沉陷发生当煤层长壁开采甚至
深度接近1000英尺。和小裂缝可以视
在面板的类型和位置的住宅住宅出现。换句话说，在长壁开采
可能有一些表面结构如房屋损坏。但它可以
保护，损害的是如此的小，除了轻微的开裂，采前和后的房屋是
几乎相同。