水平层状围岩铁路隧道地震动力响应特征研究

Research on the Seismic Response Characteristics of Railway Tunnel in Horizontal Layered Surrounding Rock

研究目的:中国汶川8.0级特大地震中,均出现了大量隧道结构的严重震害。国内学者对隧道结构抗震进行了细致深入的研究,主要集中在复杂地质及破碎地段隧道地震反应、偏压隧道与隧道洞口段地震反应、隧道抗减震研究等方面。虽然目前关于隧道与地下结构抗震分析的研究颇丰,但大多是按照均匀连续介质模型进行模拟,考虑水平层状围岩特性的隧道结构动力响应分析还不多见。本文基于连续介质力学的离散元方法软件CDEM模拟水平岩层的结构面特性,主要针对不同水平岩层的厚度和不同地震动输入方向,共计12种计算工况,分析隧道衬砌关键部位的动力响应特性。研究结论:(1)结构面(层面)存在会引起主应力增加,产生相对位移,降低加速度,尤其对穿越中厚层状围岩的隧道要加强措施;(2)地震动方向对隧道衬砌大主应力的影响比较明显,特别对拱顶、墙腰、仰拱的大主应力(压应力)影响比较大,对拱顶的影响尤其明显,且岩层越薄,影响越大;(3)地震动方向对隧道衬砌拱顶的拉应力影响特别大,在竖向地震作用下,拱顶的拉应力将超过1.54 MPa,当岩层层厚为0.2 m时将超过2.66 MPa,已经超过了混凝土的抗拉强度,水平层状围岩隧道拱顶衬砌需加强;(4)该研究结论对类似地质条件下地下工程的建设具有指导意义。

Research purposes： During Wenchuan MS 8.0 earthquake in China, a large number of tunnel structures have serious damage. Scholars at home and abroad have carried on many detailed researches on the seismic behavior of tunnel. Most of those researches mainly focused on the seismic responses of complex geology and broken surrounding rock, the response of bias tunnels and tunnel portals, and the tunnel resistance and damping researches. Although studies on seismic analysis of tunnels and underground structures are quite abundant, most of them were simulated by using homogeneous continuum model, few researches had been dedicated to the dynamic responses of tunnel linings in consideration of the characteristics of horizontal layered surrounding rock. In this paper, 12 kinds of different working conditions were considered in the view of different thickness of horizontal stratum and different direction of the earthquake ground motion inputting, the effects of the seismic responses of railway tunnel linings and the most unfavorable seismic responses of the key parts of linings were analyzed by using the numerical simulations based on Continuum- based Discrete Element Method（CDEM） code.Research conclusions and the acceleration. ：（ 1 ） Structural plane can cause the principal stress increase, and produce relative displacement Therefore, when the tunnel had to cross through stratified surrounding rock, its supporting structure should be strengthened, especially when the thickness of stratified surrounding rock is thicker. （2） The direction of ground motion on the impact of major principal stress of tunnel lining is more obvious, especially to the vault, waist and back wall, the influence is especially obvious to the vault, and the thinner of the rock stratum, the bigger of the effect. （3） The direction of ground motion has a great influence on the tensile stress of vault. Under the vertical seismic action, the tensile stress in the vault will be greater than 1.54 MPa. When the thickness of horizontal rock layer reaches to 0.2 m, the tensile stress will come to more than 2.66 MPa, then it will beyond the tensile strength of the concrete. Therefore, the lining on the vault should be put more attention. （4） This study may be a reference for the design of this underground engineering in horizontal layered surrounding rock.