关键词: 预应力锚索桩板墙, 隧道洞口边坡, 降雨、地震, 动力响应, 振动台试验

Abstract: The tunnel slope is prone to be damaged under the action of earthquakes and rainfall. It is necessary to study the dynamic response characteristics of the reinforcement structure of the tunnel portal slope. A tunnel portal slope in southwest China is experimentally studied as an example. The dynamic response and failure mode of the tunnel portal slope reinforced by prestressed anchor sheet-pile wall under earthquakes and rainfall are analyzed through shaking table test. The main conclusions include: (1) The failure process of the slope can be summarized as: tension cracks at the slope crest-shear cracks shear cracking, the foot of the slope, and overall sliding failure of the slope. Under the seismic action, the local damage occurs easily near the slope surface due to the infiltration of rainfall. The failure mode is tension-shear. (2) The peak acceleration amplification factors along the pile shaft increase significantly with the increase of peak acceleration, thus the inertial amplification effect of the structure should be considered properly. (3) The peak earth pressures behind the pile increase as the input peak acceleration becomes larger and the earth pressure changes from the S-shaped distribution to the inverted triangle distribution. When the peak acceleration is greater than 0.4 g, the axial force of anchor cable increases gradually and the tension effect is fully exerted. (4) The amplitude of Fourier spectrum of soil pressure and acceleration of pile are concentrated in the low frequency band. There is a high-frequency filtering effect of seismic wave propagation along the elevation. (5) The displacement spectrum amplitude of the pile increases as the peak acceleration becomes greater and increases larger along the pile height. The main frequency of the displacement spectrum is 1–4 Hz and the dominant frequency is 2.5 Hz, which is close to the dominant frequency of the seismic load. (6) The correlation between pile accelerations is well related and the correlations of pile acceleration, dynamic soil pressure, strain and axial force of anchor cable decrease with the increase of peak acceleration.

Key words: prestressed anchor sheet pile, tunnel portal slope, earthquake and rainfall, dynamic response, shaking table test