高铁列车荷载作用下桩网复合地基振动特性模型试验

桩网复合地基是高速铁路广为应用的基础形式之一，其在高速列车荷载作用下的振动响应对列车运营安全和周围环境有着至关重要的影响。基于此，以现浇X形桩为对象，建立了桩网复合地基大比例尺模型，开展了桩网复合地基在高铁列车荷载作用下的动力响应特性研究，揭示了加载频率、加载幅值及振次的改变对桩网复合地基振动速度影响的规律。试验结果表明：速度响应幅值沿着路堤横向衰减较快，路堤耗能作用显著，列车运行产生的振动对周边环境影响较小。速度响应幅值沿桩网复合地基深度方向的衰减规律与横向振动传播规律有所不同。速度响应幅值从轨道板与钢筋混凝土底座到基床表层，衰减最快；加筋碎石垫层次之，相当于一个隔震垫层；地基中桩的存在使振动衰减变得缓慢，使由列车运行引起的振动影响深度加大。速度响应幅值随着加载频率的增加而逐渐变大，在25 Hz时出现峰值；速度响应幅值随着加载幅值的增加逐渐变大；速度响应幅值随着振次增加而基本保持不变。

Piled embankment model test on vibration characteristics under high-speed train loads

A piled embankment with reinforcement is one of embankments widely used by high-speed railways. The effect of vibration velocity response under train loads of high-speed railways on train running safety and surroundings is crucially important. A large-scale piled embankment model was set up with X-section cast-in-place concrete pile as vertical reinforcement. The vibration performance of the piled embankment under train load of high-speed railways was investigated. The influence of loading frequencies, loading amplitudes, and the number of cycles on vibration velocity of the piled embankment model was revealed in this paper. The results show that it is faster for attenuation of vibration velocity along the transverse direction of the piled embankment. The impact of the embankment on energy dissipation is remarkable, so the effect of vibration induced by train running on surroundings is weaker. The attenuation of vibration velocity along the piled embankment depth is different from the transverse direction of the piled embankment. The piled embankment system shows the greatest attenuation of vibration velocity is from track slab and reinforced concrete base to surface layer of subgrade bed. The gravel cushion with geogrids attenuates less due to shock isolation cushion. The piles in the foundation make attenuation of vibration velocity by train running slower and influence depth deeper. Vibration velocity amplitude increases gradually with the increase of loading frequency, and reaches a peak at 25 Hz. It becomes bigger step by step with the increase of loading amplitude and stays the same with the increase of the numbers of cycles.