5. Abutment Reinforced by Geogrid and Cement Treated Backfill with High Seismic Performance

      Large differences in level on embankments at the rear sides of abutments may arise due to the subsidence caused by the backfill and the inclination of the abutment itself under earthquake shaking (Fig. 1). Since such subsidence seriously affects vehicle running stability, the necessity of preventive measures has been pointed out. In particular there has been a growing demand for development of a new type of cost-effective abutment providing sufficient seismic performance against extreme earthquake motion. The Railway Technical Research Institute (RTRI) has proposed a completely new abutment structure concept offering dramatically increased seismic performance by conducting a series of model tests with shaking table on a range of abutment-reinforcing work.
      The proposed abutment, known as the abutment reinforced with geogrid and cement treated backfill by Geogrid and Cement Treated Backfill with High Seismic Performance, has a structure in which a cement-stabilized approach block is used for the embankment on the rear side, with the approach block and abutment body linked by geotextile reinforcing material (Fig. 2). This resolves the differences in level found in the boundary between abutment and embankment on the rear side, dramatically improving earthquake resistance. Since the body section and foundation can be made slimmer by sharing earthquake forces with the reinforcing material, construction costs can be reduced to between twenty and thirty percent less than conventional abutments.
      A design method for this abutment was proposed, and actual abutments were built for the Kyushu Shinkansen (Fig. 3). The abutment will be adopted as the standard structure for all projected Shinkansen lines.
      This research was conducted in conjunction with the University of Tokyo and the Japan Railway Construction Public Corporation (JRCC). The research results are regarded as a product of the basic research institution at the Corporation for Advanced Transport & Technology (CATT).

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