EFFECTS OF THRUST PROTECTING METHOD FOR BURIED PIPE USING GEOGRID GABION OF DIFFERENT SIZES

Abstract

On the bend of a buried water supply pipeline, the thrust force is applied to the ground. A concrete block is typically installed at the bend section of the pipeline as a thrust protection measure. However, a concern exists that the stability of the concrete block might not be maintained when the ground around the concrete block liquefies during an earthquake. In this study, thrust protection using a gabion composed of a geogrid basket and gravel as a pressure-receiving structure to protect against thrust force is proposed. Further, the effects of this method are evaluated by conducting model experiments. In the model experiments, a constant load simulated thrust force was applied laterally to a buried pipe model in the model ground where the internal effective stress was decreased by increasing hydraulic gradient stepwise. Gabion models of several widths were placed on the ground in the direction of the thrust force. Results revealed that the gabion stabilizes the pipe even when the effective pressure of the surrounding ground decreases significantly and that the behavior of gabions in the ground is affected by their width. Moreover, the requirements for a gabion to improve a pipe’s stability will be discussed herein, based on the results of several test cases.