地裂缝场地下地铁振动荷载传播特性试验研究

Model test on surrounding rock vibrating response under metro tunnel crossing ground fissure

为了研究地裂缝场地下地铁列车振动荷载在围岩土体中的传播规律及其对隧道结构的影响,以西安地铁为工程背景,采用1∶20的几何相似比,开展了地铁隧道与地裂缝30°斜交的围岩动力响应物理模型试验,测试分析了在不同频率和不同振源位置下,围岩加速度及隧道应变的变化规律.结果表明:地铁列车振动荷载的频率为20 Hz时,围岩的振动响应最为明显;当振动频率大于40 Hz时,随着频率的增加,围岩振动响应变化不明显.地裂缝对列车振动荷载的传播有一定的影响,当振动位于上盘时,随着距离地裂缝越近,振动逐渐减小,在地裂缝处衰减更明显;当振动位于下盘时,同样随着距离地裂缝越近,振动逐渐减小,但穿越地裂缝进入上盘后,振动几乎没有衰减,即上盘对振动有一定的放大作用.研究结果可为研究地铁运营安全及地面建筑的防振减振控制提供参考.

To study the surrounding rock vibrating response and the influence of tunnel structure from metro vibration with tunnel crossing the ground fissure, a physical model based on Xi＇an Metro was tested. The tunnel crossing the ground fissure with 30° and a geometrical scale of 1： 20 was tested. The surrounding rock vibrating response and the deformation regulation of tunnel from different vibration sources or frequencies were studied. The test results show that the vibrating acceleration of the soil and tunnel is the strongest with its vibration frequency at 20 Hz, and the vibrating acceleration of the soil and tunnel does not change obviously when the frequency is more than 40 Hz. The ground fissure affects the surrounding rock vibrating response. The acceleration is decreased as the wave drift towards the fissure as the vibration source is in the upper plate, especially in the ground fissure. However, the acceleration in the upper plate is not changed as the vibration source is in the lower plate. The ground fissure has a magnifying effect on the vibration propagation of trains. Thus, it provide a reference for the metro studying of operation safety and vibration reduction of building.