Model experiments for propellant embedded rock anchors

Summary Propellant embedded anchors can be used to secure offshore platforms by rapidly anchoring them in seafloor rock. Field tests conducted by the U.S. Navy showed inconsistent results. A more promising approach seems to be modelling of anchor penetration and pullout resistance in jointed rock based on first principles.In this paper, physical model tests are described with which the physical phenomena are investigated and which will serve as a basis for predictive analytical models. The laboratory experiments, conducted with fasteners to model the anchors and with jointed and intact rock models made from gypsum, showed that basic intact material properties, joint configuration and individual joint properties influence penetration and pullout resistance. If the behavior is brittle, penetration is accompanied by cracking, otherwise ductile continuum deformation occurs. Jointing affects cracking in that closer joint spacing restricts cracking to fewer joint bounded plates but increases the number of cracks in the individual plate. The increased cracking intensity leads to a reduced pullout resistance.For purposes of analytical modelling, one can therefore, in a first step, build upon established relations between intact meterial, joint geometry and individual joint characteristics.