| The interaction among piles, reinforced cushion and soil is strong within geosynthetic-reinforced pile-supported embankments. Especially when the height of embankment is low, the train load has a big influence on roadbed. The soil arching effect and tensioned membrane effect within the embankment will change under train load and it will disturb the function of geosynthetic-reinforced pile-supported embankments. So it is significant to research the soil arching effect and the characteristics of geogrids within the embankment under train load.The paper made a mesoscopic research on soil arching effect within simplified geosynthetic-reinforced pile-supported embankment by using PFC3d software firstly. Then the paper proceeded with a study on soil arching effect and characteristics of geogrids under train load within geosynthetic-reinforced pile-supported embankments constructed based on the test section of Sui-Yu line by using ABAQUS software. The main contents and conclusions of the paper show as follows.1. The paper has made a mesoscopic research on soil arching effect within simplified geosynthetic-reinforced pile-supported embankments by using PFC3d, the results show that the stress arch will appear in the subgrade while the differential settlement occurs between piles and soil among piles and there exist a few virtual arches under the stress arch. The dynamic arch will appear in the subgrade under train load. The height of dynamic arch is related to dynamic load and it is lower than the static soil arch. Within the scope of displacement arch, the horizontal displacement of particles on the top of piles is largest. The formation of plane of equal settlement is related to the displacement arch. Within the scope of displacement arch, the particles above piles squeeze into the area above soil between piles and it leads to the decrement of vertical displacement of particles above soil among piles and to the increament of particles above piles outside the displacement arch.2. The dynamic finite element model for geosynthetic-reinforced pile-supported embankment has been built by ABAQUS software. The conditions such as train load, dynamic boundary and so on are set by corresponding methods. The comparison between calculate results and test datas in situ verifies the viability of the model. 3. The paper has analyzed the change law of the vertical stress distribution, height of plane of equal settlement and pile-soil stress ratio within geosynthetic-reinforced pile-supported embankments under train load basing on the dynamic finite element model. The results show that soil arching effect can affect the dynamic distribution in embankment under train load. The dynamic stress above soil among piles transfers to top of piles, and this phenomenon is most obviously in the vicinity of geogrid. In the process of train load, the peak of the stress concentration ratio decreases to a stable value. The height of plane of equal settlement of longitudinal section which has piles is higher than that of longitudinal section which has no piles. The height of the plane of equal settlement of same longitudinal section decreases gradually along the center of embankment to shoulder of the embankment. After train load, the height of the plane of equal settlement in the center of the subgrade increase. Additionally, the influence of factors such as pile spacing, the height of embankment, the modulus of soil behind the end of piles on analysis parameters of soil arching effect and their variation after train loading has been analyzed.4. The deformation and stress of geogrids under train load has been analyzed. The results show that the vertical displacement of geogrids above soil among piles is larger than that above piles in the center of subgrade. The deformation and deformation variation of lateral geogrids is greater than that of longitudinal geogrids. The dynamic displacement of longitudinal geogrids which is perpendicular to edge of caps is larger than that which is parallel to edge of caps. The dynamic displacement of lateral geogrids decreases gradually along the center of subgrade to the toe of slope. In the center of subgrade, the stress and dynamic stress of geogrids above the edge of caps is larger than that above center of caps and soil among piles. The biggest stress and dynamic stress of lateral geogrids is larger than that of longitudinal geogrids. Compared to single geogrids, double geogrids can decrease the settlement and differential settlement of subgrade and improve the ability of subgrade to resist the differential settlement caused by train loading. Also double geogrids is benefit to the stability of stress under train loading. Additionally, the influence of factors such as pile spacing, the height of embankment, the modulus of soil behind the end of piles on deformation and stress of geogrids and their variation after train loading has been analyzed. |
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