可液化地层狮子洋盾构隧道横向地震响应规律及减震措施研究

Transverse seismic responses of Shiziyang shield tunnel in liquefiable soil and its shock absorption measures

基于有效应力分析法,运用有限差分程序FLAC2D对可液化地层狮子洋盾构隧道在不同地震波激励、不同入射方向下的地震响应和地基加固减震效果进行研究和评价,为类似工程抗震设计和施工提供理论指导。结果表明:在等强度的不同地震波作用下,结构地震响应的总体规律基本相同,只是由于地震波的频率特性和持时不同,结构响应峰值到达时刻亦不同;同一地震波、不同入射方向下,结构内力的分布、发展规律差异较大,水平地震作用对结构的破坏性明显比竖向垂直地震波大;在100年2%概率水平地震作用下结构最大拉、压应力分别为1.61MPa和10.13MPa,分别发生在拱顶和右侧环偏下约45°的位置;结构满足抗震要求,但衬砌顶部拉应力达到了结构抗拉强度的85.2%,应采取加固措施;基于多种加固方案的对比研究,认为狮子洋隧道地基加固范围取5m,地基强度参数提高至原来的2倍较为经济合理。

Based on the effective stress analysis method, the seismic responses of Shiziyang shield tunnel in liquefiable soil, under the condition of different seismic excitations and different incident directions, are studied by a finite difference code--FLAC2D, along with shock absorption effect of strengthening the foundation soil. The results of numerical simulation indicate that the characteristics of seismic responses of linings under different types of seismic waves with the identical intensity are in substantial agreement, except that the time when the maximum responses occur is not consistent because of different waves with different frequencies and durations; the distribution and development of structural internal force vary much with the incident direction of waves. It is obvious that the damage due to horizontal earthquake action is much heavier than that due to vertical earthquake action. The crown and the position at an angle of about 45 degrees to the vertical central axis of lining structure are the very place where the maximum tensile stress, 1.61 MPa, and the maximum compressive stress, 10.13 MPa, appear respectively. Shiziyang shield tunnel meets the requirements for transverse seismic resistance but the reinforcement is still needed for the tensile stress at the crown, which has reached 85.2 percent of its tensile strength. According to the comparative studies on several layouts of reinforcement, the economical and rational way for Shiziyang shield tunnel is 2 times the strength of the soil surrounding lining at the range of 5 m.