Dynamic Response Of Retaining Embankment Under Seismic Excitations

The successful application of geogrid is hopeful to lessen some common embankment hazards in highly seismic regions and improve the earthquake-resistance capability of highways. By the Dali-Ruili railway's project. This dissertation studys reinforced earth embankment aseismatic research both here and abroad widely.For practical engineering problems, utilize Wenchuan earthquake's damage data, with vibration table test in-door, Use FLAC3D geotechnics software to analysis reinforced earth embankment's response law under earthquake, and use static method calculate embankments'safety coefficient of different slope gradient,and then comparison with the experiment data, some conclusions are made blow.1) The seismic hazard investigation of the embankment engineering in Wenchuang earthquake shows that embankments with geogrids's aseismatic is better than the embankments without geogrid,and its damage only display local deformation.With earthquake effect intensity increasing, the embankment's damage pattern form slope crack horizontally to local collapse and finally embankment whole slippage.So,guarantee the slope's stability is particularly important for the embankment's aseismatic. Certainly, the order of severity of the embankment are directly related to reinforcement measure,earthquake intensity2) Through safety analysis of embankments of different slope gradienst, compare with the computed results, further confirms the discovery of the seismic hazard investigation of the embankment engineering in Wenchuang earthquake—the embankments with geogrids's aseismatic is better than the embankments without geogrid. The current code for design of railway embankment formulate except adamant block stone stuffing, the slope gradienst of embankment is between 1.75 and 1:1.5. By calculating, under normal operating conditions, the embankments with geogrids and the slope gradienst is between 1.75 and 1:1.5, its safety coefficient have been much higher than 1.15. The embankments with geogrids and when its the slope gradienst is between 1.2and 1:1, with slope gradienst increasing, the safety coefficient of embankment reduce fast, non-linear. So in this range increase the slope gradienst needs carefully checking.3) Through the large shaking table simulation experiment, it is found:during earthquake.reinforced embankment surface seismic pressure peak along the embankment height is observed as curve sharp, most for "W" curve shape. To observe the peak pressure reach the maximum in 0.6 times slope height, toe of slope and the top are both observed decreasely relative central height. The static pressure of slope surface is near to zero, so in the earthquake effect, soil pressure reach its biggest value at 0.6 times height, and is designed to strengthen for protection as important part.4)Found by numerical simulation, the embankments with geogrids and when its slope gradienst is 1:2 between 1:1.25, as slope gradienst reducing, the dynamic earth pressure incremental of embankment's slope growing. On the one hand, the greater the slope, the smaller the gradient, and at the same height, the volume is bigger, then the seismic force affect the slope more. On the other hand,the smaller the gradient, the smaller the deformation under earthquake.the slope release, the less the seismic earth pressure the slope release and the bigger force itself bear.