The Lance Insertion Retardation meter (LIRmeter): An instrument for in situ determination of sea floor properties-technical description and performance evaluation

摘要

Within this paper we present the Lance Insertion Retardation meter (LIRmeter) as an instrument to determine the strength of marine sediments by a measurement of the deceleration of a probe during penetration into the seafloor. The instrument has been designed for the penetration of the upper 4 m of marine sediments and is therefore suitable for site investigation applications such as cable route surveys. The LIRmeter can be easily deployed from a floating platform in water depths of up to 4,500 m. The system is suitable for long lasting missions (more than 12 h) with pogo-style measurements due to a rugged design and a special selection of sensors and electronics. The LIRmeter provides a custom data acquisition software and a web interface for acquisition setup, data download and system administration. An adaptation of the instrument to specific problems (i. e. extremely soft sediments) is possible due to interchangeable tips and adjustable weights of the lance. The specifically developed user interface and the rugged design make the instrument very easy to handle and to maintain. The sensors and the data acquisition were tested in the laboratory as well as in the field. Field measurements took place in the North Sea, where numerous measurements were performed. This paper gives an extensive description of the design of the LIRmeter (mechanics, electronics and data acquisition) supplemented by a description of data analysis and results of field- and laboratory-tests.