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

The Detection System of Geotechnical Multi-parameter for Test-mining Area of Natural Gas Hydrate
Ziqiang Rena,b , Jiawang Chen a,b, Xiaohui Hua,b, Hang Zhoua,b, Feng Gaoa,b, Yuhong Wang a,b,*aHainan Institute, Zhejiang University, Sanya, China
bOcean College, Zhejiang University, Zhoushan, China*Corresponding author: Yuhong Wang

These features can cope with the problem of insufficient accuracy ofhydrate investigation and identification by conventional methods.
Therefore, it has a very broad application prospect in the field ofhydrate exploration (Wang et al, 2019). In addition, investigation andresearch of seabed soil mass properties are essential important parts ofocean engineering construction such as offshore oil platforms, seabedtunnels, oil and gas pipelines, optical cables and the like (Mckay et al,2018).
At present, most static sounding technical equipment adopts a straightrigid probe rod with the whole length to directly press a probe into thesurface of a seabed, so that radial instability and operation
inconvenience are caused, and the static sounding technical equipment
is not suitable for exploration of deep seabed sediments; and in addition,
due to the adoption of a segmented probe rod mode, manual butt joint isneeded, large operation labor requirements exist, and the detection
method is only limited to shallow water operation environments and is
not suitable for deep sea areas (Lunne et al, 2010).
Therefore, a seabed geotechnical in-situ multi-parameter detection
system is designed, the requirements of accurate survey technology andequipment for seabed soil mass properties are met, survey work of theseabed soil mass properties is carried out under the large working water
depth of the deep sea, meanwhile, the survey depth is further improved,
and the level of marine geotechnical engineering in-situ survey
equipment in China can be improved.

ABSTRACT.
This article mainly presents the mechanism of a new method of seabed
cone penetration test (CPT) in acquiring soil properties for Natural Gas
Hydrate (up to 30 m depth). This new method of seabed CPT system
can realize the automatic docking and dismantling of the probe rods
underwater, which greatly reduces the workload of manual docking andimproves the survey efficiency.

KEY WORDS: Natural Gas Hydrate, seabed CPT, soil
properties.
INTRODUCTION
Natural gas hydrate (NGH), commonly known as "combustible ice", ischaracterized by wide distribution, abundant reserves, and high energy
density (Ren et al., 2020). However, the sediments in which gas
hydrates are stored may be subject to explosive decomposition due tocertain factors, or the free gas may cause changes in the soil propertiesof the sediments, such as the compressibility, shear strength andpermeability of the sediments, which may lead to secondary
engineering geological hazards such as drilling safety, methane leakage,
ground subsidence and submarine landslides (Lunne et al, 2009; Koh etal, 2012).
Assessment of the risk of engineering geological and environmental
hazards require a good knowledge of the mechanical behaviour of soils
and of their spatial variability. In-situ survey techniques can detect
different physical properties of sediments with different probes, which
can assess risk of engineering geological and environmental hazards(Seifert et al,2008). Such information can be best obtained from aproperly planned program of both laboratory and in situ tests. The two
methodologies are very much complementary rather than competitive.
However, in situ tests can often be preferable to laboratory tests
because of important advantages such as cost—time effectiveness, theability to assess the soil in its natural environment and the possibility toestimate the spatial variability of the deposit (Lunne et al 2007; Ron etal, 2011).
The interpretation of test data can be applied to survey of NGH.
Different data can reflect sediment type, temperature gradient, acousticproperties, presence of natural gas, state of emplacement, influence
factors affecting seismic data discrimination, chemical anomalies, etc.

COMPOSITION AND MOVEMENT MECHANISM OF
DETECTION SYSTEM
Such detection system is designed for depths of 4,500 m and canachieve survey depth of 30m. As shown in Fig.1, the seabedgeotechnical in-situ multi-parameter detection system mainly includes
an integral frame, the constant-speed penetration mechanism of proberods, the storage mechanism of large-capacity probe rods, the transfer
mechanism of probe rods, the automatic docking and dismantlingmechanism of probe rods, counterweight, as well as the supporting
hydraulic drive system and control power supply system. The constantspeed penetration mechanism is set at the center of the overall
installation to push the rod into and out of the soil. The automatic
docking and dismantling mechanism is placed at the top of theconstant-speed penetration mechanism. The transfer mechanism and thestorage mechanism are respectively fixed on both sides of the constant-

1537