Scheduling the work |
Clients often ask how many vibracores can be collected in a day. The coring itself -- vibrating the tube in and pulling it out -- takes only a few minutes. The great majority of time in a vibracoring survey is spent on other activities: moving from point to point, negotiating bridges, locating the station, 3-point anchoring, preparing to core, handling the sample, delivering it to shore, resupplying, etc. To the extent that all of these logistics can be streamlined, the vibracoring goes faster. On the average, under "normal" conditions, the sampling takes about an hour per station. Of course, this does not include the usual "mob" and "demob" activities at the beginning and end of the survey: launching and retrieving the boat, setting up and breaking down the rig. At project sites with difficult access, extra deployment time may be needed. For example, if no boat launch facilities are available, the boat may be lifted in and out by mobile crane, with additional set up required. Or multiple launches may be neccessary if the waterway is blocked to navigation in places. Finally, it is always prudent to schedule an extra "weather day" or more to cover any unforeseen delays in the field. Fortunately, sediments are a conservative medium, and generally their sampling need not be scheduled around some short term event. |
