During the drivage of main-gate in long-wall face with fully mechanized caving mining, the gate is hard to support due to its loose and broken roof, large cross-section and long span.

在综采放顶煤工作面顺槽掘进过程中，由于顺槽煤层顶板松动破碎，并且顺槽采用矩形断面，顶板跨距较大，不利于巷道支护。

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This paper analyzes the success application influence factors about the roof caving technology of cantilever support and summarized it's main factors.

对影响悬移支架放顶煤技术成功应用因素进行了系统分析，并总结出了其主要影响因素。

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Forward support bolt combined with roop rock by bolting can play a roll of combined beam, which can prevent roof rock caving immediately after explosion.

超前支护锚杆锚固后与顶板岩石构成一体，这样使超前锚杆形成组合梁作用，放炮后，能够阻止顶板岩石冒落。

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Now, I say all this not to re-litigate the past, but it's simply to state that the component parts of the Recovery Act are consistent with what many of you say are important things to do -- rebuilding our infrastructure, tax cuts for families and businesses, and making sure that we were providing states and individuals some support when the roof was caving in.

WHITEHOUSE: President Obama Takes Questions at GOP House Issues Conference | The White House