SMALL PROTOTYPE TEST IN TRONDHEIMSFJORD

Small prototype testing was performed in Trondheimsfjord in August 2003.  Two anchors of approximately 1/3 the expected average full size anchor i.e. 4.4m long and approximately 2.8 tons, were machined and fabricated at REINERTSEN Orkanger for testing and verification of the procedures involving prototype installation and anchor behavior during deployment and service. The test was carried out on borehole G08 in a proposed gas pipeline route through Trondheimsfjord to Skogn, about 5,5 nautical miles from Port of Trondheim.

The test program is divided into to parts i.e.

1. an installation part comprising preparation for anchor launching, anchor launching and drop to seabed, and
2. anchor pullout capacity as a function of drop height (penetration), consolidation time and direction of loading from chain/mooring line.

The anchor was instrumented with:

• one accelerometer for monitoring the anchor velocity changes throughout the drop and soil penetration phase in addition to determining the total penetration depth through the sediments,
• two pressure sensors for measurement of pore water dissipation with time at two points on the anchor,
• an inclinometer to determine verticality
• one depth sensor.

The tests were well carried out and satisfied its goals which are to implement and execute the proposed procedures and associated equipment for fabrication, transportation and installation of the anchor. Furthermore, the geotechnical assessment to verify the anchor penetration depth and holding capacities was conducted. The pull-out-tests were carried at time 0 (right after drop), 1 week after drop, and 2 weeks after drop, both laterally and vertically. In general, the results from the test conformed the expected capacity of such DPA.