地震荷载下砂层隧道围压分布响应与上浮机制离心模型试验研究

    Centrifuge Modeling of the Seismic Response of Lining Earth-Pressure Distribution and Uplift Mechanisms for Tunnels in Sand

    • 摘要: 围压是隧道设计、施工和运营安全评价的重要力学指标之一,目前埋置深度和地震荷载对隧道围压分布特征的影响与非线性变化规律,尚缺乏深入认识与探讨。设计开展了一组不同埋深砂层隧道离心模型试验,对比了各离心加速度下浅埋、深埋两种隧道的围压分布特征与变化规律,揭示了地震荷载对不同埋深隧道的围压分布影响及与周围土体的相互作用,阐明了不同的上浮机制和动力行为。结果表明:1)静荷载下浅埋和深埋隧道围压分别呈蝴蝶形与龟背形分布,最大和最小压力均位于下拱脚与拱顶;两种规范法的理论围压计算值随深度呈线性增长,实测值则为非线性分布,规范法整体趋于保守。2)动荷载下隧道围压发生重分布,浅埋和深埋隧道围压分别呈蝴蝶形与四角星形分布;浅埋隧道上拱脚围压增幅最大,拱顶增幅最小;深埋隧道上拱肩围压增幅最大,拱腰增幅最小。3)在0.1g、0.3gEl-Centro和0.1g等幅正弦荷载下,两埋深隧道围压各部位呈增长趋势,浅埋和深埋隧道围压分别在拱底和下拱肩显著增长,而规范法计算则偏于保守,经历多次震动后隧道服役安全性和寿命周期评估仍值得重视。4)在0.3g等幅正弦荷载下,隧道出现一定上浮和土-结相对运动,浅埋隧道除拱腰其余部位均呈负增长,推断为等效密度差引起的浮力上浮机制;深埋隧道下拱肩呈负增长,其余部位呈正增长,推断为等效密度差和隧道挤压引起的动力耦合上浮机制。

       

      Abstract: Earth pressure on tunnel linings is a critical mechanical factor for the design, construction, and safety assessment of tunnels. However, the impact of burial depth and seismic loading on the distribution and nonlinear variation of earth pressure remains insufficiently explored. This study presents a series of centrifuge model tests on tunnels in sand at different burial depths, comparing the distribution and variation of lining pressure under centrifuge scaling. The tests reveal how seismic loading influences earth pressure distribution, emphasizing soil-structure interaction, uplift mechanisms, and dynamic behavior at varying depths. The key findings are as follows:1) Under static loading, the lining pressure of shallow and deep-buried tunnels exhibits butterfly-shaped and tortoise-shell-shaped distributions, respectively; the largest and smallest pressures occur at the lower springline and the crown. Two code-based calculation approaches predict pressures that increase linearly with depth, whereas the measurements are nonlinear; overall, the code methods are conservative. 2) Under dynamic loading, the lining pressure redistributes: shallow-buried tunnels retain a butterfly-shaped pattern, while deep-buried tunnels develop a four-pointed-star pattern. For shallow-buried tunnels, the upper springline shows the greatest increase and the crown the least; for deep-buried tunnels, the upper shoulder exhibits the greatest increase and the waist the least. 3) Under 0.1g, 0.3g El-Centro, and 0.1g sinusoidal loads, the pressure increases at various tunnel locations. In both shallow and deep tunnels, significant pressure growth occurs at the tunnel floor and lower shoulder, respectively. Standard method calculations remain conservative. After multiple seismic events, the tunnel’s operational safety and life cycle assessment remain crucial. 4) Under a 0.3g sinusoidal load, some uplift and relative motion between soil and structure are observed. In the shallow tunnel, all sections except the waist show negative pressure growth, likely due to buoyancy uplift. In the deep tunnel, the lower shoulder exhibits negative pressure growth, while the rest show positive growth, attributed to dynamic coupling and compression.

       

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