In-flight Simulation of Pile Installation in Slopes in Centrifuge Model Tests

A new device was developed to simulate the in-flight installation of jacked displacement piles in slopes using centrifuge model tests. In the modularization-based design of this device, the pile installation process is divided into combinations of five-axis movements, which are realized by corresponding electric motors. New structures consisting of combined cubes and cylinders are proposed for the pile top and the picking-up unit. In addition, this device utilizes a series of techniques, such as the use of linear guideways, to increase digital control and the local stiffness of key structures. These measures provide a high degree of automation with good accuracy in determining the locations and vertical extents of piles during installation. The structures and electric motors in the device were optimized to provide high capacities for the load (10 kN) and displacement (260 mm). This device was designed with hollow components to control the size and mass of the entity (only 50 kg) and to satisfy rigorous requirements regarding the allowable deformation and stability levels during centrifuge model tests. The effectiveness of the device was verified using pile installation tests under various conditions. The test results were compared with results that were obtained using pre-flight pile installation. Overall, the pile installation method influenced the responses of the pile-reinforced slopes. For example, the loading-induced displacement of the slope with piles installed in-flight was considerably greater than that in the slope with piles installed at the 1g level when the load was near the limit.