沉管隧道–接头–场地土振动台试验研究

为了解沉管隧道及其接头在地震作用下的动力响应,以中国广州洲头咀沉管隧道工程为背景,在北京工业大学九子振动台台阵系统上开展了1∶60比例尺大型沉管隧道–接头–场地土振动台模型试验。试验中模型箱采用装配式连续体刚性模型箱,其尺寸为7.7 m(长)×3.2 m(宽)×1.2 m(高),试验中输入地震动时程采用El Centro、Taft、天津及广州人工地震动记录,输入方向为水平横向和水平纵向一致地震动激励。设计了用于模拟沉管隧道接头的构件,并利用拉压传感器和激光位移计测得接头处所受轴向力及变形。结果表明:不同段模型结构测得的加速度及其傅立叶幅值谱有差别,且隧道结构地震响应不是随其自身特性振动,而是服从于周围土体的地震响应;不同强度地震动激励下,不同接头的受力情况可以为沉管隧道的抗震设计提供有价值的参考;不同强度地震激励下,不同接头的位移变化趋势基本上遵循J1接头位移最大,J3接头位移次之,J2接头位移最小,由于J2接头位于中间,这样的变化规律使得整个隧道沿纵向变形更加协调;水平纵向和水平横向一致地震激励下,每个接头的正反方向位移变化趋势基本平行,本次试验结果换算到原型结构,隧道接头止水带处于安全范围不会漏水。

Shaking table tests on immersed tunnel-joint-soil

To obtain the dynamic response of the immersed tunnel and its joints under seismic action, with Zhoutouzui immersed tunnel project in China as the background, a series of shaking table tests on immersed tunnel-joint-soil with a scaling factor of 1/60 are conducted under uniform earthquake excitation by using the multiple shaking table test system in Beijing University of Technology. They are performed using a rigid prefabricated continuous model box with the dimensions of 7.7 meters long, 3.2 meters wide and 1.2 meters high. The test system is subjected to strong ground motions from El Centro record, Taft record, Tianjin record and Guangzhou artificial record through horizontal longitudinal and horizontal transverse uniform seismic excitations. The model tunnel joint components are designed to simulate the immersed tunnel joint, and the axial force and deformation of joints are obtained by using the pull-press sensors and laser displacement sensors. The test results show that the acceleration time histories and their Fourier spectra of different model tunnel segments are different from each other. And the seismic response of the tunnel structure is not vibration along with its own features, but is subject to the seismic response of the surrounding soils. Under the seismic excitation with different intensities, the force distribution of joints can provide valuable reference for aseismic design of the immersed tunnels. Under different seismic inputs with different intensities, the displacement of joint 1 is the maximum, and that of joint 2 is the minimum. Such change law makes the whole tunnel along the longitudinal deformation more harmonious. The change trend of displacements along the positive and negative directions at each joint is basicly parallel. The practical water stop of tunnels is in a safe range and will not leak by converting the test results to the prototype data.