新建隧道下穿高速公路动力响应及变形控制研究

为揭示上部重型汽车振动荷载对立体交叉工程结构稳定性的影响,依托祁家庄隧道近接下穿既有G6高速公路工程,结合重型汽车运动微分方程建立的基于现场振动实测激励输入模型,运用连续介质快速拉格朗日差分分析法,研究重型汽车振动荷载作用下公路路基体、围岩夹层和下部隧道结构的动力响应特性和变形规律。结果表明,在重型汽车进入和驶离目标断面时,路基监测点动位移曲线呈现周期性变化且存在汽车荷载叠加效应,最大动位移达2.93 mm;隧道开挖促进应力-应变滞回圈的形成,加剧振动波能量的损失,动应力累计衰减0.248 kPa;重型汽车荷载引起的振动效应是造成下部隧道拱顶沉降的主要原因,其最大变形达0.226 mm;采用循环进尺为2 m的上下台阶法,可保证交叉段上部公路及下部隧道的安全和稳定。

Study on Dynamic Response and Deformation Control of a New Tunnel under the Expressway

In order to reveal the influence on stability of the three-dimensional cross engineering structure induced by the vibration load form the heavy duty vehicle, the paper was based on the existing number G6 highway project undercrossed by Qijiazhuang Tunnel, and adopted the Fast Lagrangian Analysis of Continua and the differential equation of motion of heavy duty vehicle to build a numerical model by the field vibration measured excitation input. And the dynamic response characteristics and deformation laws of subgrade, surrounding rock interlayer and tunnel structure under the condition of vibration load are studied. The study shows that the dynamic displacement curve of subgrade changes periodically and vehicle load exist superposition effect when the heavy duty vehicle drives to the target section and leaves, and the maximum dynamic displacement is 2.93 mm. Tunnel excavation promotes the formation of stress-strain hysteresis loop and the energy loss of vibration wave, which reflects the cumulative attenuation of dynamic stress is 0.248 kPa. The vibration effect caused by the load of heavy-duty vehicles is the main cause of the settlement of the lower tunnel vault, and the maximum deformation is 0.226 mm. The safety and stability of the upper highway and the lower tunnel in the cross section can be guaranteed by using the benching method with the 2 m cycle rulers.