Application of end bearing and friction piles for geosynthetic-reinforced pile supported embankment method for high-speed concrete track

초록

The problems associated with constructing high-speed railways on soft soil led to the development and extensive use of many ground improvement techniques. Design criteria of residual settlement of embankment is limited to 30 mm or less for high-speed concrete track, it is very difficult to satisfy such standard using traditional method. Geosynthetic reinforced pile supported embankments (GRPS method) have been widely used throughout the world because of its settlement-constraining effect and reduction in construction cost and time. GRPS method consists of vertical columns that are designed to transfer the load of embankment through the soft compressible soil layer to a firm foundation and one or more layers of geosynthetic reinforcement placed between the top of the columns and the bottom of the embankment. As for the economical efficiency, cost reduction as much as 40%, compared to bridge is expected. Also GRPS is a very rapid for constructing embankment over soft soil. The mechanism of the technique allow for immediate embankment construction in a single placement stage. Pile supported embankments have been actively applied in China, more than 50 km for Situ line, Hada line and also Beijing - Tianjin high-speed line. Because the soft soil is widely distributed in the south-east region of China, even the friction piles (CFG) and geosynthetic with low tensile strength were found to have sufficient strength to contain track settlement. This study intends to evaluate the settlement characteristics of GRPS embankments by design condition (geosynthetic design, service load, pile spacing) as part of measurement to satisfy the requirement of allowable residual settlement as well as to develop the design technology. Numerical analysis was performed using the program Plaxis 2D and Plaxis 3D Tunnel.