ABSTRACT The poor performance of jetting and trenching techniques in non-cohesive soil was the incentive for KS EPL to develop another technique specifically designed for pipeline burial in areas where the sea or river bottom consists mainly of sand. In this new technique the bottom adjacent to the pipeline is fluidised over such a length that the pipe, having lost its support, sags to the desired depth owing to its flexibility and the load exerted by the fluidising device resting on the pipeline. The pipeline can be buried to considerable depths in one pass and is covered immediately. INTRODUCTION All submarine pipeline 'burying methods and equipment that have appeared in ever increasing numbers in recent years have one thing in common: t hey require the preparation of a ditch or trench in which the pipe is lowered during the operation oil afterwards. Most methods can be applied successfully in sea beds consisting of cohesive soil such as clays. In cases where the sea bed is noncohesive (e. g. sand) the trench will fill up rapidly, resulting in a too small burial depth of the pipeline. A new method has now been developed at Koninklijke/Shell Exploration Productive Laboratorium, Rijswijk (the Netherlands) for thoseareas where the sea bottom consists mainly of sand. This method involves fluidisation of the bottom adjacent to the pipeline over such a length that the pipeline, having lost its support, sags to the desired depth, aided by its flexibility and the load exerted by the fluidising device resting on the pipeline. The sea bottom under the pipeline is fluidised by water flowing under low pressure from holes in the lower girders of the horse-shoe shaped device straddling the pipeline The device may be equipped with submsersible pumps, although in shallow waters supply by hoses from a workship is to be preferred. APPLICATION The method was applied for the first time for burying a 12.5 mile long 6×0.280" gas line in the Dutch Waddenzee in 1971. The device used was about 24 m long and water was fed to the device via hoses from the work barge. The water consumption for fluidisation was approximately 2000 US gal/min at 20 psi. After some teething troubles the method proved to work very satisfactorily: the pipeline was eventually buried to a depth of 6 ft at a rate of 13 ft/min. As the Waddenzee is a tidal sea, burial was only possible during high tide. The total operation took 21 days. After burial the sea bed was found to be perfectly flat and it was difficult to locate where the pipe had been buried. In 1973 some flowline crossings had to be buried in Nigeria. Although laboratory tests had demonstrated that both bundles of pipes and single lines can be buried by the fluidisation technique, it was decided to bury the flowlines individually.