16、 根据位移-时间曲线判断 ,当d2u/d2t<0时,表明围岩已进入危险状态。×√恭

16、 根据位移-时间曲线判断 ,当d2u/d2t×√恭

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— I.d like to take a look first at those structura

— I.d like to take a look first at those structural support beams that were goin

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