In situ instruments

Information concerning the shallow water free-fall CPT probe (SW-FF CPT, maximum depth of operation: 200m) can be found in the following article:

Stegmann et al., 2006 (Sea Technology)

 seatech_stegmann_copy.pdf

Article published in Sea Technology, v. 47/2, p. 27-33

The maximum depth of operation for the deep water free-fall CPT (DW-FF CPT) is 4000m. Until now it has operated at depths of max. 2000m off Chile, Uruguay, in the Mediterranean Sea (Cretan Sea, Ligurian Sea), and in the North- and Baltic Sea.
Containing two differential and one absolute pressure sensors, it can measure pore-pressure at two different depth levels and hydrostatic pressure.
To facilitate a maximum degree of flexibility, the DW-FF CPT was designed to run either autonomously or by telemetry via a ship's wire. The system has been recently improved with a 1 kHz data logger and improved design (v2).

Since 2009, a piezometer probe developed at IFREMER Brest, France is part of the equipment pool of MARUM Marine Geotechnics. The instrument, a version 2 design, is modularly designed and reaches u to 7m length. The individual piezo modules comprise KELLER differential pressure transducers and thermistors, which are connected by cabled metal rods of 75 cm or 150 cm length. Deployment is achieved using a weight set (IFREMER) either by winch on a wire, or as long-term deployment. On the base plate, pressure housings contains the batteries as well as data logging unit and the hydrostatic pressure port for reference. The instrument is used to monitor typical decay curves of pressure after deployment, or processes such as seismicity, deformation or fluid flow.

At the FINO1 research platform, the MARUM Bremen runs an underwater docking-station, which can supply up to 10 instruments with power- and data connections.
The FINO1 platform represents a sea-bed observatorium, where instruments and sensors can be long-term tested. The docking station wa sretrieved in July 2009 for maintenance and will later be deployed again in the North Sea.

NIMROD is a self-contained shallow water (200m) free falling penetrometer to characterize the sea floor with regard to its stiffness. It is handled very easily owing to its low weight and independence from ship equipment (e.g. winches) Thus, it is especially designed for rapid deployments from small boats and in areas where a deployment of standard-instruments is difficult because of high waves, strong currents, vicinity to installations, etc. Strong ship movements are not critical anymore because NIMROD is free falling.

The penetrometer is equipped with acceleration sensors (1.7 g, 18 g, 70 g, 250 g), tilt sensors, a pressure sensor, and a 1kHz data logger. It offers a choice of three different tip geometries (cone, cylinder, hemisphere) to allow a better adjustment to different types of sediments. Previous deployment include areas such as North Sea, Baltic Sea, and several harbours.

In September 2006, a pore pressure-lance was connected to the underwater docking station, which itself is attached sea-bed near to a steel-girder of the FINO1 platform. This lance can measure pore-pressure and temperature in the first 2 meters below the sea-bed. It was developed to investigate if pore-pressure changes can be detected when the platform moves (e.g. during stormy events) and if the movement of the platform has any impact on the stability (liquefication) of the sediments close to the foundation.

In 2007, a 360° scanning sonar tower equipped with an Imagenex 881L sonarsystem was developed at MARUM Bremen. It scans a radius of up to appx. 200 m at programmed intervals to monitor sediment dynamics and remobilisation. The modular tripod allows the user to install teh sonar 3 m or 5.5 m above sealevel to monitor over tidal cycles or even months. Areas of interest include estuaries, tidal inlets and dune fields in German Bight and North and Baltic Sea.

Two instruments were installed in July 2007 in Azerbaijan, to monitor the activity of Dashgil mud vulcano close to teh Caspian Sea coastline:
- a 2m-long pore-pressure and temperature lance
- two gas flow-meter,
all in teh main crater lake of the actively venting feature.

For details, see chapter in Projects and Research areas.

Borehole-Monitoring using so called CORK systems (Circulation Obviation Retrofit Kits) has been successfully carried out for almost two decades within the scientific marine drilling programmes ODP and IODP As a simpler approach preceding the CORKs, two "smart plugs" were developed together with colleagues from Pacific Geoscience Centre, Canada (Earl Davis, Bob Macdonald, Alison Labonte, Bob Meldrum) and Pennsylvania State University, USA (Demian Saffer) in 2009. The instruments measure pore pressure and temperature variations in the cased, partially perforated Borehole before the final CORK is installed.

The so called "smart plugs" are part of a mechanical separation in teh casing (bridge plug) that decouple the ocean water body from the well hydrologically. They are self-contained instruments which are retrieved prior to CORKing. The aims include monitoring of pore pressure variations in fault zones. Each "smart plug" contains 2 Paroscientific absolute pore pressure transducers with Bennest period counters as well as 4 temperature transducers. The first deployment occurs during IODP Expedition 319 with the NanTroSEIZE (Nankai Trough Seismogenic Zone Experiment) project, whose foremost objective is to unravel seismogenic processes in teh subduction zone offshore Japan.