框架梁与锚索桩板墙加固隧道洞口边坡的动力响应特性

Dynamic Response Characteristics of Tunnel Portal Slope Reinforced by Frame Beam and Anchor Cable Pile Sheet Wall

针对山岭隧道洞口在降雨、地震等因素作用下易产生变形破坏的问题,以某处采用框架梁与锚索桩板墙支护的隧道洞口边坡工程为原型,开展几何比尺为1∶50的振动台模型试验,分析降雨后地震作用下边坡的动力响应特性及失稳变形规律。结果表明:降雨后坡面无局部破坏,地震作用下边坡的破坏过程可归纳为坡顶张拉破坏—坡脚剪切溃裂—坡体整体失稳滑动,边坡表现为张拉—剪切型破坏;边坡峰值加速度放大系数呈层状分布,“高程效应”与“趋表效应”显著,均随输入正弦波频率、幅值的增加而增大;边坡土体峰值应变分布与坡体滑动破坏面较吻合;桩体锚索轴力与输入正弦波频率、幅值呈正相关,强震作用下锚索轴力增幅显著;桩后峰值土压力近似呈三角形分布,桩体嵌固段内桩土压力最大;桩体弯矩呈“b”型分布,嵌固段内桩体峰值弯矩最大,抗震设计中应注意验算其抗弯强度;桩后土压力与桩体加速度FFT谱幅值主要集中于低频段,结构动力响应主要受地震波低频段部分影响。

In order to solve the problem that the mountain tunnel portal is prone to be deformed and damaged under rainfall,earthquake and other factors,based on a place taking the tunnel portal slope project supported by frame beam and anchor cable pile sheet wall as the prototype,a shaking table model test with a geometric ratio of 1∶50 is carried out to analyze the dynamic response characteristics and instability deformation law of the slope under earthquakes after rainfall.The results show that there is no local damage on the slope surface after rainfall,the damage process of the slope under earthquake can be summarized as tensile damage at the slope crest-shear collapse at the slope foot-the instability and sliding of the overall slope,and the slope exhibits the mode of tension-shear failure.The Peak Ground Acceleration(PGA)amplification factors of the slope present a laminar distribution,and the“elevation effect”and“skin effect”are significant,which amplify with the increase of frequency and amplitude of input sine wave.The peak strain distribution of slope soil is consistent with the slope sliding failure surface.The axial force of pile anchor cable is positively relative to the frequency and amplitude of input sine wave,therefore,its axial force increases significantly under strong earthquakes.The peak earth pressures behind the pile are approximately triangular in distribution,and the pile earth pressure is the highest inside the embedded section of the pile body.The bending moment of the pile body exhibits“b”type distribution,and the peak bending moment is the highest inside the embedded section,so attention should be paid to verify its bending strength in the seismic design.The amplitudes of FFT spectrum of earth pressure behind pile and acceleration of pile body are mainly concentrated in the low-frequency band,and the dynamic response of structure is mainly affected by the low-frequency band of seismic waves.