Model Test Study on Dynamic Response of Expressway Plastic-Reinforced Earth Embankment under Earthquake

Aiming at the seismic response of plastic geogrid-reinforced embankments, with Zhounan Expressway as the research engineering background, a self-designed seismic-rainfall coupled slope model test system was designed and used to produce 1 : 20 scale plastic geogrid-reinforced embankments. Moreover, the physical model of the unreinforced embankment under Hanshin wave, Wenchuan wave, Tianjin wave, etc. was also studied to carry out comparative analysis on seismic response and dynamic response on test model. The dynamic characteristics and dynamic response of the embankment model were tested from low to high seismic intensity; the changes of the embankment’s natural frequency, damping ratio, acceleration at the measuring point, and dynamic earth pressure were analyzed; and the main influencing factors and damage to the embankment seismic response feature were discussed herein. The test results showed that the initial natural frequency of the reinforced embankment was 42.4% higher than that of the unreinforced embankment, and its initial damping ratio reduced by 19.4%. The attenuation effect of the natural frequency and damping ratio of the reinforced embankment with the loading history was significantly lower than that of the unreinforced embankment. Embankment reinforcement exhibited a very good inhibitory effect on the PGA amplification effect of the embankment, and the inhibitory effect on the interior of the slope was more significant than that on the slope. Moreover, the type of seismic wave, the amplitude of the seismic wave, and the frequency of the seismic wave significantly influenced the PGA amplification effect of the embankment. The peak dynamic soil pressure of the unreinforced embankment at the same location was significantly greater than that of the reinforced embankment. The two embankment models showed significantly different antivibration damage performance. After the peak acceleration of 2 m s-2 was loaded, no cracks were seen on the surface of the embankment model. When the peak acceleration of 3 m s-2 was loaded, on the slopes of the two embankment models, smaller cracks were observed in the middle and upper parts of the face. When the peak acceleration of 4 m s-2 was loaded, the failure of the unreinforced embankment model was obvious. Large cracks on the top of the slope could reach 16 mm in width, and 27 mm settlement appeared at the top, and the slope was convex. The reinforced embankment model was only on the slope shoulder. Moreover, there were fine cracks on the top, and the slope top settlement was less than 5 mm. The research results provide theoretical support for preventing and controlling the road embankment vibration diseases and improving highway durability design.