沉管隧道振动台模型地震反应试验研究

为研究沉管隧道在饱和砂土场地中的地震反应规律,以某超长沉管隧道为研究对象,设计了装配式柔性橡胶接头,开展了饱和砂土中的多段式沉管隧道振动台模型试验。沉管隧道模型由3节微粒混凝土管段和两节装配式柔性橡胶接头构成。试验通过孔隙水压力计、加速度计和应变片监测了地基的孔压、结构及其周围土层加速度和结构应变。试验结果表明:中小震时地基土并未液化,大震时模型表层地基土发生液化。地基土液化后,低频地震波对结构影响更大。结构与周围土体的加速度及其傅里叶谱形状吻合较好,结构加速度小于土体加速度,沉管隧道结构的地震反应受地基土的影响较大。靠近接头监测点的加速度反应更大,管段之间出现相对运动,接头是沉管隧道抗震设计的关键部位,模型结构的中墙、侧墙与结构顶板节点为此类型隧道的不利位置。试验研究成果为隧道抗震研究提供参考。

Shaking table model test study on seismic response of animmersed-tube tunnel

In order to study the seismic response law of the immersed － tube tunnel in the site of saturated sand，an extra-long immersed-tube tunnel is taken as the study object，and then a type of prefabricated flexible rubber joint is designed for carrying out the shaking table model test of the multi-segment immersed-tube tunnel. The model of the immersed-tube tunnel consists of three micro-concrete tube segments and two prefabricated flexible rubber joints. By means of pore pressure gauge，accelerometer and strain gauge，the pore pressure and the structure as well as the acceleration and structural strain of the surrounding soil layer of the foundation are monitored through the test. The test results show that the foundation soil is not yet liquefied during mid-small earthquake，but the model foundation surface soil is liquefied during large earthquake. After the liquefaction of the foundation soil，the impact from the low-frequency seismic wave on the structure is even great. The structure is better coincided with the acceleration of the surrounding soil mass and the shape of its Fourier spectrum，while the structural acceleration is less than that of the soil mass，thus the seismic response of the structure of the immersed-tube tunnel is largely impacted by the foundation soil. The acceleration response near the monitoring point of the joint is larger along with the relative motion between the tube-segments，thus the joint is the key position for the seismic design of the immersed-tube tunnel，while the nodes among the mid-wall，the side wall and the roof of the model structure are the unfavorable locations for this kind of tunnel. The study result can provide references for the seismic study of tunnel concerned.