Development of a P-Wave Transponder System for Tracking Buried Objects in 1-g and Geotechnical Centrifuge Models

Abstract

Locating and tracking buried objects underground can be a difficult task especially in the case of plate anchors in soft clays. These plates, used offshore, gain their large vertical capacity by being embedded deep into the seafloor. Most commonly they are installed by either dragging horizontally tens to hundreds times their fluke length (drag embedment anchors) or by a suction caisson, which is then removed, and then dragging the anchor multiple fluke lengths, (suction embedded plate anchors). They can be extremely cost effective given their capacity to weight ratios, but they also have significant uncertainty in their capacity since plate anchor installation depths are exceedingly difficult to measure and predict. These difficulties exist not only in the field, but also in the laboratory. In the past decade significant progress has been made towards measuring plate anchor kinematics in 1-g laboratory experiments with the development of magnetometer tracking systems and translucent soil simulates. However, these methods are not easily transferable to the geotechnical centrifuge, where models with field scale effective stresses can be tested. In this paper we propose a new method for tracking plate anchors within a soft clay small scale model using an acoustic transponder attached directly to the plate anchor. We demonstrate the systems feasibility with analytical calculations and a prototype experiment in water. Though this active acoustic system is being developed for plate anchors in clay it could be used to detect the location and trajectory of any object buried in soil.