Design of a Robot and Test Procedure for the Dynamic Testing of Anchorages in a Geotechnical Centrifuge

The design of a novel robot for the dynamic testing of ground anchorages in a geotechnical centrifuge is presented. The structure tested comprises nine pretensioned anchorages in a 3×3 array, installed in dry sand, supporting a retaining wall. The anchorages are partially threaded and have washers and nuts installed so that the amount of load can be varied by tightening the nuts against the wall. The purpose of the robot is to move to the head of anchorage during operation of the centrifuge, locate onto the nut, rotate it by a prescribed amount to change the load, disengage from the nut, and then apply an impulse to the end of the length of anchorage protruding from the wall. The resulting vibration response is measured by an accelerometer and captured by a data acquisition system for processing to investigate the effect of load on the dynamic response of the anchorage. The robot has four degrees of freedom, three linear motions, and one rotation and includes a solenoid operated impulse-generating device. The design specification and detailed structure of the robot are presented along with commissioning tests to prove the effectiveness of the system before deployment on an extensive test program.