Proceedings of the Thirty-second (2022) International Ocean and Polar Engineering Conference
Shanghai, China, June 5–10, 2022
Copyright © 2022 by the International Society of Offshore and Polar Engineers (ISOPE)
ISBN 978-1-880653-81-4; ISSN 1098-6189

www.isope.org

Design of In-situ High-precision Terrain Deformation Data Acquisition System on the SeabedPeng Zhou, Xiaoqing Peng, Dongrui Ruan, Chen Cao, Jiawang Chen*
Ocean College, Zhejiang University.
Zhoushan City, Zhejiang Province, China

method combining global positioning and navigation system detection
system uses the sensor array to send a wide range of sound waves to theseabed, and then uses the receiving sensor array to receive narrow beamsound waves. The advantage is that the operation is relatively simple andcan accurately describe the three-dimensional characteristics of seabedterrain (Jreng, 2012), but it needs to be carried by scientific research
vessels, ROVs or AUVs, which is difficult to achieve real-time, longterm and in-situ monitoring. In view of the topographic survey in the testarea of gas hydrate in the South China Sea, some scholars have proposed
topographic subsidence measurement schemes, including gravity
acceleration measurement system and water pressure measurement
system (Yokoyama.2012; Woolsey, 2006). The gravity acceleration
measurement system is used to monitor the seabed settlement before andafter the hydrate test. The measured acceleration value is used for thesecondary integration to obtain the seabed settlement. In the waterpressure detection system, the pressure sensor is installed on the seabedsurface, and the measured pressure directly reflects the depth of the water
body. Both gravity acceleration measurement system and water pressure
measurement system are only single point measurement. At present,
there is still a lack of an in-situ and long-term surface morphology
monitoring system that can well monitor the topographic subsidence ofthe hydrate test mining area.

ABSTRACTWith the gradual depletion of non-renewable energy sources such as coaland oil on the earth, natural gas hydrates, which are abundant in marine
sediments, are considered to be a clean strategic replacement energy inthe future. In this paper, a set of in-situ high-precision terrain
deformation data acquisition system for seabed is designed, and thesystem can also be used for monitoring and early warning of geologicaldisasters in active areas of seabed geological plates. The system caneffectively monitor seabed terrain deformation in gas hydrate mining
area, and provide data support for seabed safety assessment in gas
hydrate mining process.

KEY WORDS: Seabed terrain deformation; data collection; hardware;system design.

INTRODUCTION
Natural gas hydrate, also known as combustible ice, is a solid substanceformed by methane gas and water dissolved in sediment pores at a certain
low temperature and high pressure. Its reserves on the earth areconsiderable, which is about twice as large as those of oil, natural gas
and coal. Especially in the ocean, it has been detected and found in morethan 80 oceans around the world so far (Kvenvolden, 2001). However,
the exploitation of natural gas hydrate in the ocean is faced with severe
security problems, because the decomposition of natural gas hydrate will
greatly disturb the structure of sediments containing natural gas andwater, and greatly reduce the strength of sediments, which is extremely
likely to cause large-scale landslides, earthquakes and serious instability
and destruction of marine structures on the seabed (Locat, 2002; Sultan,2004).

The seabed in-situ high-precision terrain deformation data acquisition
system designed in this paper uses high-precision MEMS sensors andencapsulates them. According to the arrangement of multiple nodes infour directions, the multi-node array is composed. The collection anddischarge function of seabed in-situ is implemented through thematching winch, and it is placed in the gas hydrate test area in the South
China Sea for six months of seabed in-situ real-time monitoring. The
original characteristic data of submarine terrain deformation in the testarea are successfully collected. The successful acquisition of highprecision terrain deformation data shows that the system has the ability
to collect and store in-situ data at a certain depth. It provides reliable
technical support for commercial exploitation of natural gas hydrate in
the future.

At present, the seabed terrain subsidence monitoring technology includes
satellite remote sensing monitoring, multi-beam sonar, side-scan sonar,
and the detection method combining global positioning and navigation
system detection system. Satellite remote sensing monitoring, multibeam sonar and side scan sonar have the advantages of all-weather, large
monitoring range and easy processing of image data. They can be used
for real-time, continuous quantitative and fixed-point monitoring. The
disadvantages are low resolution and high cost of long-term observation,
which are not suitable for underwater terrain monitoring. The detection

System design
Structure and process design592