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The failure propagation of weakly stable sediment:A reason for the formation of high-velocity turbidity currents in submarine canyons

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Journal of Oceanology and Limnology 2023年第1期41卷 100-117页

作者： Yupeng REN Yi ZHANG Guohui XU Xingbei XU Houjie WANG Zhiyuan CHEN Shandong Provincial Key Laboratory of Marine Environment and Geological Engineering Qingdao 266100China Shandong Provincial Key Laboratory of Marine Environment and Geological Engineering Ocean University of ChinaQingdao 266100China key laboratory of marine environment and Ecology Ocean University of ChinaMinistry of EducationQingdao 266100China

The long-distance movement of turbidity currents in submarine canyons can transport large amounts of sediment to deep-sea plains.Previous studies show obvious differences in the turbidity current velocities derived from the multiple cables damage events ranging from 5.9 to 28.0 m/s and those of field observations between 0.15 and 7.2 m/s.Therefore,questions remain regarding whether a turbid fluid in an undersea environment can flow through a submarine canyon for a long distance at a high speed.A new model based on weakly stable sediment is proposed(proposed failure propagation model for weakly stable sediments,WS S-PFP model for short)to explain the high-speed and long-range motion of turbidity currents in submarine canyons through the combination of laboratory tests and numerical analogs.The model is based on two mechanisms:1)the original turbidity current triggers the destabilization of the weakly stable sediment bed and promotes the destabilization and transport of the soft sediment in the downstream direction and 2)the excitation wave that forms when the original turbidity current moves into the canyon leads to the destabilization and transport of the weakly stable sediment in the downstream direction.The proposed model will provide dynamic process interpretation for the study of deep-sea deposition,pollutant transport,and optical cable damage.

关键词： turbidity current excitation wave dense basal layer velocity WSS-PFP model

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Shear Strength and Dilatancy of Calcareous Sand in the South China Sea

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China Ocean engineering 2022年第5期36卷 781-790页

作者： PEI Hui-min WANG Dong Shandong Provincial Key Laboratory of Marine Environment and Geological Engineering Ocean University of ChinaQingdao 266100China Qingdao National laboratory for marine Science and Technology Qingdao 266100China

The shear strength and dilatancy of typical uncemented calcareous sand from the South China Sea are investigated by soil lab tests.According to drained triaxial tests at various relative densities and confining stresses,it is found that the constant volume friction angle is approximated as 39°and the traditional Bolton’s equations can be modified to estimate the peak friction angle and dilation angle.The reliability of the equation proposed for the peak friction angle is verified in terms of calcareous sands from more onshore and offshore sites worldwide,while the errors of the predicted dilation angles scatter in a relatively large range.Totally,the dilation angles of sands in the South China Sea are estimated by the equation presented with an error of±30%.The peak friction angle measured by the undrained is similar to that by the drained tests as the relative density smaller than 60%,while the former is slightly lower for denser samples.

关键词： calcareous sand triaxial tests friction angle dilatancy drained South China Sea

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An Innovative Approach to Predicting Scour Depth Around Foundations Under Combined Waves and Currents in Large-Scale Tests Based on Small-Scale Tests

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Journal of Ocean University of China 2023年第3期22卷 637-648页

作者： HU Ruigeng LIU Hongjun LU Yao WANG Xiuhai SHI Wei College of environmental Science and engineering Ocean University of ChinaQingdao 266100China key laboratory of marine environment and Ecology Ministry of EducationQingdao 266100China Shandong Provincial Key Laboratory of Marine Environment and Geological Engineering Qingdao 266100China School of Civil engineering Qingdao University of TechnologyQingdao 266033China

This study presents an innovative theoretical approach to predicting the scour depth around a foundation in large-scale model tests based on small-scale model tests under combined waves and currents.In the present approach,the hydrodynamic parameters were designed based on the Froude similitude criteria.To avoid the cohesive behavior,we scaled the sediment size based on the settling velocity similarity,i.e.,the suspended load similarity.Then,a series of different scale model tests was conducted to obtain the scour depth around the pile in combined waves and currents.The fitting formula of scour depth from the small-scale model tests was used to predict the results of large-scale tests.The accuracy of the present approach was validated by comparing the prediction values with experimental data of large-scale tests.Moreover,the correctness and accuracy of the present approach for foundations with complex shapes,e.g.,the tripod foundation,was further checked.The results indicated that the fitting line from small-scale model tests slightly overestimated the experimental data of large-scale model tests,and the errors can be accepted.In general,the present approach was applied to predict the maximum or equilibrium scour depth of the large-scale model tests around single piles and tripods.

关键词： scour scour depth prediction Froude similarity scale effects combined waves and currents

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Liquid-plastic Limit of Surface Sediments in North Slope of South China Sea

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Acta Geologica Sinica(English Edition) 2017年第S1期91卷 259-260页

作者： JIANG Jun ZHU Chaoqi SHEN Zhicong ZHANG Bowen ZHANG Xiatao WANG Xinquan JIA Yonggang Shandong Provincial Key Laboratory of Marine Environment and Geological Engineering (Ocean University of China) laboratory for marine Geology Qingdao National Laboratory for Marine Science and Technology

1 Introduction China has a vast area of continental shelf and is very rich in marine resources,but because of the complex geological environment and frequent geological disasters,the utilization of marine resources an... 详细信息

关键词： soil Liquid-plastic Limit of Surface Sediments in North Slope of South China Sea

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Surface Sediment Density and Moisture Content in North slope of South China Sea

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Acta Geologica Sinica(English Edition) 2017年第S1期91卷 155-156页

作者： ZHANG Bowen ZHU Chaoqi JIA Yonggang ZHANG Xiatao DAI Xinnan SHEN Zhicong JIANG Jun WANG Xinquan Shandong Provincial Key Laboratory of Marine Environment and Geological Engineering( Ocean University of China) laboratory for marine Geology Qingdao National Laboratory for Marine Science and Technology

marine engineering geology is mainly based on the actual project to study the seabed.This provides a variety of engineering geological parameters for the development of marine engineering(Zhu et al.,2016).This is an e... 详细信息

关键词： Surface Sediment Density and Moisture Content in North slope of South China Sea

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In-situ Observations of engineering geological environment during Hydrate Production Tests in Deepwater

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Acta Geologica Sinica(English Edition) 2017年第S1期91卷 193-194页

作者： ZHU Chaoqi JIA Yonggang Shandong Provincial Key Laboratory of Marine Environment and Geological Engineering (Ocean University of China) laboratory for marine Geology Qingdao National Laboratory for Marine Science and Technology

Gas hydrates are ice-like combinations of methane and water.The global inventory of gas hydrates appears to be very large.Recent estimates of the total amount of methane contained in the world’s gas hydrates range

关键词： estimates contained inventory methane hydrate mankind recovered fossil resistivity Siberia

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Runout of submarine landslide simulated with material point method

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Journal of Hydrodynamics 2017年第3期29卷 438-444页

作者： Youkou Dong Dong Wang Mark F.Randolph Centre for Offshore Foundation Systems the University of Western Australia Shandong Provincial Key Laboratory of Marine Environment and Geological Engineering Ocean University of China

Most of the present knowledge on submarine landslides relies upon back-analysis of post-failure deposits identified using geophysical techniques.In this paper,the runout of slides on rigid bases is explored using the material point method（MPM）with focus on the geotechnical aspects of the morphologies.In MPM,the sliding material and bases are discretised into a number of Lagrangian particles,and a background Eulerian mesh is employed to update the state of the particles.The morphologies of the slide can be reproduced by tracking the Lagrangian particles in the dynamic processes.A real case history of a submarine slide is back-analyzed with the MPM and also a depth-averaged method.Runout of the slides from steep slopes to moderate bases are reproduced.Then different combinations of soil and basal parameters are assumed to trigger runout mechanisms of elongation,block sliding and spreading.The runout distances predicted by the MPM match well with those from large deformation finite element analysis for the elongation and block sliding patterns.Horst and grabens are shaped in a spreading pattern.However,the current MPM simulations for materials with high sensitivities are relatively mesh sensitive.

关键词： Submarine landslide runout morphology material point method large deformation

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Occurrence of Different Forms and Implications of Compound Specific Sterols in Continental Sediments of the Northeast South China Sea

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Acta Geologica Sinica(English Edition) 2019年第2期93卷 420-429页

作者： QIU Hong ZOU Li ZHANG Minsheng ZHU Chaoqi JIA Yonggang College of environmental Science and engineering Ocean University of China Education key laboratory fo r marine environment and Ecology Ocean University of China The Shandong Provincial Key Laboratory of Marine Environment and Geological Engineering Ocean University of China

The South China Sea(SCS) is one of the most productive and accumulative marginal shelves of organic carbon in the world. To expound the transformation and preservation of organic carbon in the Northeast SCS, where abundant oil and gas resources have been reported, compound specific sterols in free(FR), base hydrolytic(BH), and acid hydrolytic(AH) forms were analyzed in surface and columnar sediments in May, 2016. The results showed that the total contents of sterols detected ranged from 0.15 to 3.74 ppm dry weight in the surface sediments, and gradually decreased from 3.41 to0.17 ppm dry weight from surface to deep sediments, in which cholesterol(27^(△5)) was the most abundant component. Sterols mainly existed in the BH form(54.51%-74.20%), followed by the FR form(25.50%-45.49%) and then the AH form(0-3.77%) in turn, in the surface sediments. BH and FR sterols accounted for 0-49.08% and 50.92%-100% in the columnar sediments, while AH sterols were undetectable. The contents of specific sterols indicated that, the primary source of marine organic carbon was about 5 times as much as that from terrestrial input. More and more FR sterols transformed into BH sterols with increasing sedimentary depth, and BH sterols absolutely dominated in sediment depths under 25 cm. The forms of Sterols C27 were maintained at a relative consistence state, but Sterols C28 to C30 degraded gradually during the sedimentation process. It was suggested that the stability of sterols, based on the chemical structures, might be the primary factor controlling their degradation and preservation in deeper sediments. These results would help to understand the organic carbon(OC) transformation in a hydrate formation area in a marginal sea.

关键词： sterols sediments occurrence forms transformation northeast South China Sea

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Experiment and analysis of the formation,expansion and dissipation of gasbag in fine sediments based on pore water pressure survey

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Acta Oceanologica Sinica 2022年第4期41卷 91-100页

作者： Shiyun Lei Xiujun Guo Haoru Tang College of environmental Science and engineering Ocean University of ChinaQingdao 266100China Shandong Provincial Key Laboratory of Marine Environment and Geological Engineering Ocean University of ChinaQingdao 266100China key Lab of marine environment and Ecology of Ministry of Education Ocean University of ChinaQingdao 266100China

Deep-seated gas in seabed sediments migrates upwards from effect of external factors,which easily accumulates to form gasbags at interface of shallow coarse-fine sediments.Real-time monitoring of this process is important to predict disaster.However,there is still a lack of effective monitoring methods,so we attempt to apply multi-points pore water pressure monitoring technology when simulating forming and dissipation of gasbags in sediments through laboratory experiment.This study focuses on discussion of sensitivity of pore water pressure monitoring data,as well as typical changing characteristics and mechanisms of excess pore water pressure corresponding to crack generation,gasbag formation and gas release.It was found that the value of excess pore water pressure in sediments is negatively correlated with vertical distance between sensors and gas source,and the evolution of gasbag forming and dissipation has a good corresponding relationship with the change of excess pore water pressure.Gasbag formation process is divided into three stages:transverse crack development,longitudinal cavity expansion,and oblique crack development.Formation of gasbag begins with the transverse crack at the interface of coarse-fine sediments while excess pore water pressure attenuates rapidly and then drops,pressure remains almost unchanged when cavity expanses longitudinally,oblique crack appeared in final stage of gasbag evolution while excess pore water pressure accumulated and dissipated again.The variation curve of excess pore water pressure in gas release stage has saw-tooth fluctuation characteristics,and the value and time of pressure accumulation are also fluctuating,indicating the uncertainty and non-uniqueness of gas migration channels in sediments.

关键词： pore water pressure monitoring technology excess pore water pressure gasbag cracks gas migration

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Dynamics of Bottom Boundary Layers in the Yellow River Subaqueous Delta Based on Long-Term In-Situ Observations

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Acta Geologica Sinica(English Edition) 2017年第1期91卷 369-370页

作者： ZHU Chaoqi JIA Yonggang WANG Zhenhao GUO Lei SHAN Hongxian LIU Xiaolei ZHANG Minsheng Shandong Provincial Key Laboratory of Marine Environment and Geological Engineering (Ocean University of China) Qingdao 266100 Shandong China laboratory for marine Geology Qingdao National Laboratory for Marine Science and Technology Qingdao 266061Shandong China

Objective In geo-marine science,the generalized bottom boundary layer（BBL）represents a layer between sediments and seawater.The BBL plays an important role in geological,geobiochemical,geophysical and geotechnical r... 详细信息

关键词： Dynamics of Bottom Boundary Layers in the Yellow River Subaqueous Delta Based on Long-Term In-Situ Observations

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