我国越来越多的地下工程揭示了地震系数法用于抗震计算中的局限性。当隧道埋深很小时,其计算结果偏小;埋深超过一定值后,该方法由于夸大了隧道上覆土柱地震惯性力的影响,使计算结果急剧增加,与实际震害现象严重不符,因此迫切需要对地震系数法进行修正以适应实际工程的需要。首先依据地震系数法进行抗震计算,分析其特点和存在的局限。并在Ⅳ级围岩条件下,分别采用地震系数法、反应位移法和时程分析法,对不同跨度的洞室进行抗震计算,并通过振动台试验结果验证,最终获得Ⅳ级围岩条件不同跨度下地震系数法的匕覆土柱合理计算高度,研究成果可供隧道工程抗震计算参考。
Seismic coefficient method shows its limitation used for seismic computation of underground constructions in China. The computation result is relatively small when tunnel is buried shallow very much, while the result increases dramatically when the buried depth of tunnel reaches a certain value because the inertia force of overburden soil is overestimated, so the results computed from this method is not in accordance with the seismic damage of tunnels. It is necessary to modify this method to make it better fit for the practical engineering. In this paper, the seismic calculation based on seismic coefficient method is carried out, and the limitation of the method is analyzed. Then seismic coefficient method, seismic deformation method, and time history analysis method are applied to tunnels' seismic calculation in surrounding rock of class Ivat different width of the cavity. The results of shaking table test are also used to verify the computation results. Finally, the advisable calculation heights of tunnel overburden soil with seismic coefficient method in surrounding rock of class Ⅳ are presented, which is helpful in seismic calculation of tunnel.