In recent years, it has often been necessary to reinforce existing foundations to perform track addition work, remodel stations or improve the earthquake resistance of existing structures. It has been difficult, however, to execute such work using existing large construction machines as work sites are normally confined, have limited overhead clearance and are located close to existing tracks. The RTRI therefore developed a method of reinforcing foundations using a battered pile composed of a small-diameter steel pipe inserted into soil cement at an angle (Fig. 1). For this purpose, the RTRI first implemented a horizontal loading test on a 1/10-scale foundation model, confirming that the bearing capacity of a vertical pile foundation was drastically improved when remodeled as a compound foundation with a battered pile (Fig. 2).
   To confirm the ease of execution of this method, the RTRI performed execution and horizontal loading tests using a 5m-long battered pile inclined at 45º. The results verified that the method is suitable for spaces with low overhead clearance located close to tracks, and substantially improves the characteristics of existing foundations, even with a comparatively short battered pile. The RTRI implemented wide-ranging numerical analysis and created a chart to calculate the number and inclination of battered piles required to reinforce existing foundations against earthquakes. It was also confirmed that, compared with the conventional technique, the new method cuts reinforcement costs by 10%, makes reinforcing work easier and reduces levels of noise and vibration.