RESISTANCE FORCE AND GROUND BEHAVIOR IN THRUST PROTECTION FOR BURIED PIPES USING GEOGRID GABION

Abstract

The bend section of a buried water supply pipeline transfers a thrust force to the ground. Thus, a concrete block is typically installed at the bend for protection. However, the concrete block may become unstable when the ground around the concrete block liquefies during an earthquake. In a previous study, we proposed the use of a geogrid gabion composed of a geogrid basket and gravel as a thrust-protection method. In this method, the geogrid gabion is placed on the ground in the direction of the thrust force. It is desirable for a geogrid gabion to be installed close to the pipe. However, the pipe and gabion must be separated for the effective compaction of soil around the pipe during construction. In this study, the effects of the horizontal distance on the thrust force protection performance of the geogrid gabion were evaluated by applying a horizontal force on a buried pipe model in a saturated ground model. The results revealed that the resistance force acting on the pipe increased regardless of the horizontal distance; the resistance force acting on the pipe was highest when the pipe moved close to the geogrid gabion. Based on the relationship between the resistance and the ground behavior, the resistance force was modeled as the sum of the passive earth pressure acting on the pipe and the resistance increment due to the passive earth pressure acting on the geogrid gabion.