Guo-lin Yang

Seismic response of embankment slopes with different reinforcing measures in shaking table tests

In order to study the seismic response of the embankment slopes with different reinforcing measures, shaking table tests were performed on three embankment slope models (i.e., unreinforced embankment slope, 2-layer reinforced embankment slope and 4-layer reinforced embankment slope). Wenchuan earthquake motions and white noise excitations were performed to investigate the change of the model parameters, the horizontal acceleration response, the vertical acceleration response and the dynamic earth pressure response of embankment slopes. A comparison was made on the seismic response among the embankment slopes with different reinforcing measures. The results show that the natural frequency of reinforced embankment slope is larger than that of unreinforced embankment slope, and the reinforced embankment slope is less sensitive to seismic excitation. Horizontal acceleration response is obviously amplified by embankment slope. Horizontal acceleration magnification presents a decreasing trend with the increase of the peak value of input horizontal acceleration, and the decreasing ratio is higher for reinforced embankment slope. The vertical acceleration magnification of reinforced embankment slope is much smaller than that of unreinforced embankment slope, and the nonlinear characteristic of embankment slope in vertical direction is not as obvious as that in horizontal direction. Residual earth pressure is mainly induced at the upper part of embankment slope.

Dynamic behavior of railway embankment slope subjected to seismic excitation

To reveal the dynamic behavior of a railway embankment slope subjected to seismic excitation, a shaking table model test was performed on a 1:8 scale embankment slope. Different types of seismic wave of differing amplitudes were applied to study the dynamic behavior of the embankment slope, and white noise excitations were interspersed among the seismic waves to observe the changes of dynamic characteristics of the embankment slope. Residual deformation behaviors of the embankment slope were also investigated. The results of the tests show that the natural frequency of the embankment slope exhibits a decreasing trend and that the damping ratio exhibits an increasing trend. The embankment slope exhibits a significant amplification effect on the input acceleration, and the acceleration response differs greatly when subjected to different seismic excitations of differing spectrum characteristics. The filler of the embankment slope affects the changes of the spectrum characteristics of the seismic wave. The filler performs a filtering effect on high-frequency seismic waves and amplifies the energy of low-frequency seismic waves, especially when the frequency is close to the natural frequency of the embankment slope. A bidirectional excitation creates a greater acceleration response than a unidirectional excitation does. The seismic residual deformation of the embankment slope occurs under the seismic subsidence mode.

Test Study on Engineering Properties of Gabion Structures

In order to study mechanical characteristic of gabion meshes, engineering properties of reinforced gabion retaining wall and green reinforced gabion retaining wall, tests including air tensile tests of gabion meshes, fatigue and aseismatic tests on gabion structures were carried out. The main tensile mechanical indexes of gabion meshes, fatigue property and seismic behavior of these two gabion structures were obtained. Test results showed: Air tensile curves of gabion mesh showed a zigzag shape; Main factors influencing the dynamic deformation behavior of gabion structures were amplitude of dynamic load, vibration times and so on, and vibration frequency had no significant influence; In fatigue tests, the maximum accumulated lateral deformation occurred in the third layer for reinforced gabion retaining wall, and the fifth layer for green reinforced gabion retaining wall; Accumulated deformation ratios of gabion structures were less than 1% under fatigue load; Both of these two gabion structures were excellent aseismatic structures, and they could bear earthquake action with seismic intensity of eight.

Pullout Test Study on Interface Friction Characteristics of Reinforcements with Red Sandstone as Filler

In order to study interface friction characteristics between reinforcements and red sandstone, pullout tests were carried out. Three reinforcements were chosen: 2.2 mm gabion mesh, 2.7 mm gabion mesh and 70RE geogrid. The pullout coefficient, cohesion and friction angle of these three reinforcements were obtained. The curves of pullout friction coefficient and normal stress, shear stress and pullout displacement were established. Test results showed: Pullout friction coefficient decreased nonlinearly with the increase of normal stress; When the pullout displacement reached a certain value, shear stress tended to be stable, and most of which presented a peak value; Pullout coefficients of different reinforcements differed greatly; Double twisted hexagonal gabion mesh had better interface friction characteristic than geogrid; The smaller the diameter of gabion mesh was, the better the interface friction characteristic would be; In general, the pulling-out process of reinforcements could be divided into three stages: initial stage, developing stage and yield stage. During the test, special clamping system was installed to limit lateral deformation of specimen.