ESS_K-16-ATA
| Type | Test |
|---|---|
| Ship | L'Atalante |
| Ship owner | Ifremer |
| Dates | 18/02/2016 - 23/02/2016 |
| Chief scientist(s) | WOERTHER Patrice |
RECHERCHES ET DÉVELOPPEMENTS TECHNOLOGIQUES Centre Ifremer Bretagne ZI Pointe du Diable CS 10070 29280 Plouzané +33(0) 2 98 22 41 41 |
|
| DOI | 10.17600/16000300 |
| Objective | The techniques of coring had little evolved since the works on the giant corer (Lancelot and Balut, on 1993) or the works on a really stationary piston (Montargès and al, on 1983). The works made by Ifremer since 10 years, with a support of the IPEV, brought real progress. The corer was instrumented with sensors who measure the vertical movements and the accelerations of various parts of the corer with enough resolution. The measures made during various trial campaigns allowed to understand the dynamics functioning of the various parts of the corer and highlight the key role of the work of the piston. According to the settings: the recovery may vary by a factor of 2, the position of the sedimentary levels are not at the real place in the core. The geometry of the layers is not well preserved, the sediment sampled by suction effect is changing with the water depth and the weight in water of the corer. It can reach 20 meters for a core of 40 meters by 4000 m depth. From the measurements, a mathematical model was developed in Matlab to calculate and predict the functioning of a coring operation and to calculate the position of sedimentary layers in the core. A software called Cinema was designed to: plot the kinematics coring operations from the measurements, calculate the position of the sedimentary layers in the core, model the coring operations with single or multiple soil layers models, calibrate the mathematical model with single or multiple soil layers models, calculate abacus for coring settings. This software is patented. The three offshore research vessels from Ifremer who perform piston coring are benefiting from this works. The recent replacement of the main cable from the Atalante vessel need to redo some corings at different depths to calibrate the mathematical model of Cinema software. The new cable that was supplied will have a different behavior. Its elastic rebound and its influence on the trigger arm damping has a direct impact on the quality of the cores. The works are done in northern Bay of Biscay on three spots where we cored before. Each coring operation is instrumented. The measures are used to plot the kinematics of the coring operations. The mathematical model from Cinema software is then calibrated with the kinematic obtained at different depths. Cores will be opened and then described by a sedimentologist to measure their exact length, estimate their quality and ensure that the perturbed sections may correspond to the sampling phases in stationary, over or under sampled mode. |
