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Front. Struct. Civ. WDemands and challenges for construction of marineinfrastructures in ChinaHuajun LIa,b*, Yong LIUa,b, Bingchen LIANGa,b, Fushun LIUa,b, Guoxiang WUa, Junfeng DUa, Huimin HOUa,Aijun LIa, Luming SHIaaCollege of Engineering, Ocean University of China, Qingdao 266100, ChinaShandong Province Key Laboratory of Ocean Engineering, Ocean University of China, Qingdao 266100, China*Corresponding author. E-mail: huajun@ouc.edu.cnb The Author(s) 2022. This article is published with open access at link.springer.com and journal.hep.com.cnABSTRACT The oceans are crucial to human civilization. They provide core support for exploitation and utilizationof marine space, resources, and energy. Thus, marine infrastructures are vital to a nation’s economic sustainabledevelopment. To this end, this article first describes the main challenges in current ocean utilization, and then reviews theChina’s ocean engineering progress. As such, six major sectors are evaluated: 1) global climate change and marineenvironment, 2) comprehensive utilization of marine space, 3) marine transportation infrastructure interconnection,4) ocean clean energy development and maricultural facilities, 5) ecological crisis and marine engineeringcountermeasures, and 6) marine infrastructure operation safety and maintenance. Finally, perspectives on futuredirections of ocean utilization and marine infrastructure construction in China are provided.KEYWORDS marine infrastructures, ocean engineering, exploitation of marine resource, coastal development, emergingmarine industries, technological challenges1 IntroductionThe oceans occupy 71% of the earth’s surface, about 40%of the world’s population lives within 100 kilometers ofthe coast, 70% of economic activities occur in coastalzones, and more than 80% of international trade is carriedout by the seas. Meanwhile, the oceans contain abundantresources relating to biology, energy, minerals, medicine,water, space, etc. The demand for marine resourcesresults in expansion of human activities, from coastalzones and continental shelf shallow waters to deep seasand polar regions. Furthermore, the oceans play anincreasingly essential role in national political andeconomic strategies.Marine infrastructures provide the key support forocean space utilization, resources exploitation, andenergy recovery. They, are crucial to the sustainableeconomic development and maritime defense security.Marine infrastructures mainly include seaports, artificialislands, coastal protection structures, oil & gas platforms,Article history: Received Feb 19, 2022; Accepted Mar 19, 2022offshore wind power installations, mariculture pastures,cross-sea bridges, subsea tunnels, etc. [1]. These infrastructures are bulky, expensive, and operate in complexand harsh environments. Failures and instabilities ofmarine infrastructures may cause serious casualties,economic losses, and environmental pollution. Buildingmaritime defense, advancing marine ecological civilization, and implementing the “Belt and Road Initiative”,etc., have all created new demands for construction ofmarine infrastructures. The design, construction, and safeoperation & maintenance of marine infrastructures aresubjected to new technological challenges. To this end,this article assesses the urgent needs and technologicalchallenges in construction of offshore infrastructures,with the aim of providing a perspective for future oceanutilization in engineering practices.This article is organized as follows: Section 2 describesthe challenges and recent progress made in marineutilization; Section 3 elaborates the urgent needs anddevelopment opportunities of marine infrastructureconstruction in terms of six key sectors. A summary thenpoints out some future directions for technology innovation for marine development.
2Front. Struct. Civ. Eng.2 Challenges and recent progress made inocean utilizationGlobal climate change and marine-related human activities threaten the ecological environment and sustainabledevelopment of the oceans. Current ocean explorationsystems are not perfect in terms of energy efficiency,environmental friendliness, and sustainability [2]. Oceanexploitation and utilization are facing brutal challengesfrom climate change and associated environmental issuesincluding: 1) aggravating marine pollution and itsassociated secondary disasters; 2) misfunctioning ofmarine ecosystems; and 3) growing intensity and frequency of extreme sea conditions. For example, under theinfluence of global warming, the frequency of highintensity storms is expected to rise, resulting an increasedpotential damage from extreme water levels such as stormsurges. Sea level rise has been accelerating saltwaterintrusion and water pollution in coastal areas and hasincreased the risk of coastal flooding and beach erosion[3]. Frequent occurrence of extreme sea conditions maylead to heavier environmental loads, damage of coastalinfrastructures, and may threaten the safety of offshoreengineering facilities [4]. Therefore, it is urgent to buildan efficient, safe, stable, and environment-friendly marinedevelopment model and framework [5].Offshore and coastal engineering facilities feature highrisk, high-investment, and high-tech characteristics andexhibit strong sensitivity and susceptibility to changes ofocean environments. First, the marine environment ishighly complex, imposing a continuous, destructive, anduncertain load on man-made infrastructures. Secondly,marine infrastructures have various structural types fordifferent water depths where strong fluid-solid couplingand interactions exist. Lastly, offshore construction andoperation are highly risky and require high standards ofsafety design and disaster prevention. Specifically, wind,waves, currents, sea ice, etc., have a continuous couplingeffect on offshore engineering facilities and require thehigh strength and durability of main structures. Besides,more unpredictable forces such as earthquakes, tsunamis,may also devastate some marine infrastructures. Marineinfrastructures differ significantly in structural types fordifferent water depths and sea conditions. It is difficult touniform the safety assessment standards of variousmarine infrastructures, and there are high risks duringconstruction and service operations. In addition, theglobal ocean governance system is not complete, and thedevelopment of ocean resources is treated as eachcountry’s own affair. Scientific development and ecological conservation concepts are still lacking in practice.Due to the lack of scientific and reasonable MarineSpatial Planning (MSP), the conflict between oceanresource development and ecological environmentconservation, and that between short-term economicinterests and long-term living environment, have not beenwell addressed. Present-day innovative capabilities ofocean technology and equipment are insufficient to copewith the harsh environment and the high-risk challengesof deep sea. It is urgent to raise the level of oceanawareness, innovate engineering technology, upgradedevelopment concepts, develop new technologies, newequipment, and to boost the emerging ocean-relatedindustries. It is imperative to boost scientific developmentand utilization of ocean resources and build fair andsustainable blue economic conditions [6] for 1) theharmonious coexistence of humanity and ecologicalresources, 2) the sustainable development of economicand ecological resources, and 3) the balancing ofmaritime infrastructure with spatial pattern and ecologicalresources. It is important to promote sustainable oceandevelopment by switching from the “high-speed andlarge-scale” type to the “high-quality and high-benefit”type and to increase the marine “green GDP” [7].At present, China has made remarkable achievementsin ocean exploitation and utilization, especially inmaritime transportation, marine equipment and facilitiesmanufacturing, and the utilization of ocean renewableenergy. For example, several cross-sea bridges (e.g.,Hong Kong-Zhuhai-Macao Bridge, the Donghai Bridge)and subsea tunnels in coastal cities (e.g., Xiamen,Qingdao, and Shantou) have been put into service. In2020, the “Striver” submersible dived 10909 meters, arecord for China’s manned deep diving, indicating thatChina has reached the world’s leading level in the field ofultradeep manned diving [8]. Furthermore, up to 2020,China’s total installed offshore wind power capacityranked first in Asia and second in the world, and theannual installed capacity in 2020 reached 3.1 GW,ranking the first in the world [9]. In 2020, China’s firstindependently developed 10 MW offshore wind turbinewas connected to the national power grid at the XinghuaBay Phase II offshore wind farm in Fuqing, Fujian. It isthe largest offshore wind turbine in the Asia-Pacificregion and the second largest in the world [10]. Whilebreakthrough progress has been made in the design andconstruction of high-end offshore equipment, thefundamental science and technology that support thehigh-end equipment is still relatively weak, and need tobe improved, especially for design and analysis softwarewith independent intellectual property rights. TheStatistical Bulletin of China’s Marine Economy shows anoverall upward trend of marine gross production value inthe period from 2009 to 2020. However, the relativecontributions from high-tech and value-added marineemerging industries are relatively low compared to those
Huajun LI et al. Demands and challenges for construction of marine in-frastructures in Chinafrom traditional marine industries. Since emerging marineindustries are based on the development of marine hightech, they play a guiding role in the development of themarine economy for the whole country, especially in theEastern and Southern coastal areas [11]. Therefore,increasing marine scientific and technological innovationand cultivating marine strategic emerging industries arethe key directions of marine economic development inChina.3 Demands and opportunities in marineinfrastructure construction3.1 Marine infrastructure design standards under globalclimate changeSince 1970, global climate change has been rising. Theaverage global temperature has increased by 1.1 Ccompared to that before industrialization [12]. Globalaverage sea level rise rate has increased from 1.4 mm peryear from 1901 to 1990 to 3.2 mm per year from 1993 to2019. China has exceptional sensitivity and vulnerabilityto the global warming and sea level rise. From 1951 to2019, China’s annual average temperature increased by0.24 C every 10 years, and sea level rising was at a rateof 3.4 mm/year from 1980 to 2019, which is higher thanthe global average level in the same period.Although it is still in debate, most studies havesuggested that intensities and numbers of tropicalcyclones are increasing [13,14]. Marine infrastructuresthus may be exposed to a more destructive environment.Main design environmental parameters such as the wind,wave and currents are increasing. Traditional designstandards are not safe enough under current climateconditions. On one hand, the design standards need to beupgraded, for example, from return period of 100 years to1000 years or longer. On the other hand, more data fromboth observations and models are needed to enrich theparameter samples. Reanalyzed ocean meteorological andoceanographical data, such as the products by theEuropean Medium-term Weather Forecast Center, the USEnvironmental Forecast Center, and the Japan Meteorological Agency are widely used in marine infrastructuredesign. However, these data usually have a low spatialresolution covering global oceans and may underestimateextreme wind speed or wave height [15,16]. Increasedwind speeds give rise to enhanced global waves; forexample, the extreme significant wave height growthrates of the Southern Ocean and the North Atlanticreached 1.0 cm per year and 0.8 cm per year, respectively[17,18]. New numerical schemes [19] and methods toestimate design values [20] are among the most activeresearch topics in this area. In addition, sea ice and stormsurges are also affected by climate change. Water levels3and flow velocities are also key parameters for design ofcoastal infrastructures, and they are influenced by climatechange and sea-level rise significantly [21].Accompanied with the changing climate, return periodsof extreme marine events have actually been shortening[22,23]. Extreme marine events have brought seriousdisasters to economies and lives. For example, marinehazards including storm surges, huge waves, and red tidesin 2020 caused direct economic losses of 0.832 billionRMB, and 6 casualties (including missing) [24]. Designstandards for coastal and marine infrastructures should beupdated regularly in response to extreme events underclimate change.3.2Comprehensive development and use of marine spaceCoastal and marine infrastructures usually occupy a largeamount of marine space. Meanwhile, different marineactivities compete for limited marine space resources,resulting in serious problems [25]. With continuous expansion of marine development and utilization activities,conflicts between different marine activities, differentstakeholders, development, and ecological conservationhave become increasingly prominent. To achieve theintegrated, effective, and sustainable development anduse of marine space, it is necessary to plan and managemarine space, and fully consider the interactions amongdifferent activities, and the cumulative effects of theseactivities [26].MSP is an internationally recognized transparent, adaptable, and sustainable marine planning and managementtool, which can provide feasible solutions to variousconflicts in marine development and utilization activities.Specifically, MSP is a comprehensive, holistic, adaptive,ecosystem-based, and transparent spatial planningprocess. It is based on a sound scientific basis, systematicanalysis, and reasonable planning of current and futuremarine development use [27]. The purpose of MSP is toprovide a platform for decision makers, stakeholders, andthe public at all levels, based on management of multiplesustainable use, resolution of conflicts, and support forecosystem-based marine management. The aim is toachieve balanced ecological, economic, and social goals[28].The formulation and implementation of marine spatialplanning is an adaptive cyclical process [29], which needsto be dynamically adjusted according to the implementation situation. Figure 1 shows the implementation processof marine spatial planning. In a specific implementationprocess, the following basic principles should be followed[27]: establishment of a management concept based onecological priority, rational arrangement of multifunctional marine space and the utilization of multipletypes of marine resources, enhancement of the public andstakeholders’ participation in the implementation of
4Front. Struct. Civ. Eng.Fig. 1Implementation process of marine spatial planning (reproduced from Ref. [28]).supervision, establishment of cross-regional and crossdepartmental coordination and management mechanisms.However, in the actual operation process, MSP still facesmany challenges, such as major scientific and knowledgegaps, policy and legislative constraints, institutional fragmentation, environmental security and sustainable development, and the needs and expectations of stakeholder’scoordination difficulties. [29]. For this reason, in thefuture use of MSP, the following should be givenattention [27]: improvement of the ability to adapt to andrecover from global climate change and the deteriorationof the marine environment; adaptation of measures tolocal conditions; ecosystem conservation, renovation andrestoration for different sea areas; strengthening ofenvironmental observation and infrastructure constructionof oceans, coasts and islands; promotion of marinescientific and technological innovation; improvement ofocean development, utilization and conservation capabilities.Offshore oil and gas projects are taken as examples tofurther illustrate the importance of MSP and itscomprehensive use in marine space. In the design andconstruction process of offshore oil and gas developmentfacilities, it is necessary to formulate comprehensiveindicators that consider factors such as safety, costs, andenvironmental conservation, and to comprehensivelyconsider the process of construction, transportation &installation, as well as the decommissioning plan and itsimpact on the ecological environment. Projects areexpected to achieve a balance of ecosystems, costs, andsocial benefits. In the early 20th century, the UnitedStates (US) began to exploit offshore oil, and the firstabandoned oil wells appeared in the 1940s. People beganto pay attention to abandoned oil wells after the 1980s.As of November 2020, more than 31000 offshore oilwells in the US alone have been permanently abandonedor suspended. In 2020, more than 600 offshore platformsworldwide are facing decommissioning; by 2040, therewill be more than 2000 decommissioned offshoreplatforms worldwide. It will cost more than US 200billion in the next 30 years to dismantle all abandonedoffshore platforms worldwide [30]. However, research onthe ecosystem around existing offshore facilities showsthat compared with the surrounding natural environment,the number of fishes around the ocean platform is largerand the population is richer [31]. In other words, oceanplatforms can play the role of features such as coral reefsin long-term operation, and the direct dismantling ofocean structures may cause new negative effects. For thisreason, the former U.S. Marine Minerals Administrationfirst proposed the concept of “Rigs-to-Reefs” (RTR), thepurpose of which is to transform offshore platforms intoartificial reefs to maintain the local existing marineecosystem. As of 2018, more than 500 abandonedplatforms in the Gulf of Mexico have been transformedinto artificial reefs. Treatments to the local environmentinclude maintaining, overthrowing, partially demolitionand transferring of the current reef environment [32].Through the transformation and utilization of abandonedocean platforms, biological productivity has beenincreased, the conservation and restoration of deep-seacreatures have been promoted, and the cost ofdecommissioning and dismantling offshore oil and gasfacilities has been greatly reduced.
Huajun LI et al. Demands and challenges for construction of marine in-frastructures in China3.3 Interconnection of maritime transportationinfrastructuresDeep-water ports, islands and reefs, and cross-sea bridgesand tunnels are key infrastructures for maritime transportation, which play a pivotal role in social and economicdevelopment [33,34]. The construction of maritimetransport infrastructure is facing new technical challengeswith more new requirements appearing such as promotionof the joint construction of the “21st Century MaritimeSilk Road”.The construction of maritime transportation infrastructure is one of the priorities of the Maritime Silk Road.However, the sea conditions along the Maritime SilkRoad differ significantly from those of China’s offshorewaters [35–37]. The main challenges lie in 1) exposure ofconstruction sites to fully open seas with heavy designload, short construction window period, and high cost ofoperation and maintenance; 2) complexity of topographyand geomorphology, with weak foundation carryingcapacities and intense seabed erosion and depositions;3) fragility of the ecological environment. The construction of the port project on the southwest coast of Indonesia along the Maritime Silk Road provides an example[38]. Offshore construction is subjected to long waveswith periods ranging from 10 to 20 s, and the wave periodand wave height have abrupt changes. Within 24 hours,wave periods can change from 10 to 20 s, and the waveheight can change from 1 to 3.5 m. As a result, traditionalconstruction techniques and equipment cannot be applied.In response to the urgent needs and technologicalchallenges mentioned above, new offshore constructiontechnology, equipment, structure, and the correspondingengineering technology standard system are necessary forlarge-scale port construction in medium and long-periodwave areas. In view of the special dynamic environmentand evolution law of remote islands and reefs, it isnecessary to carry out in-depth research on the long-termstability of islands and reefs as well as conservationtechnologies [39].For the construction of cross-sea bridges and tunnelsunder complex and severe sea conditions, it is importantto incorporate fundamental theories and design methodsfrom multiple disciplines, including marine dynamicenvironment, marine geological exploration, marine engineering design and construction, and new marine engineering materials. In the meantime, it is indispensable tocarry out exploration and research on new cross-seapassages such as large floating bridges and floatingtunnels [40,41].3.4 Ocean clean energy and mariculture engineeringfacilitiesTo fulfill the target of reaching peak carbons emissionsby 2030 and carbon neutrality by 2060 in China,5substantial efforts have been made in the development ofmarine renewable energy. Due to the advance of marinetechnology and increasing market demand, marineemerging industries are showing a leap-forward evolution[42]. However, the design of equipment for emergingindustries remains challenging because of the complexmarine environmental conditions and limitations indesign theories. Offshore wind power and offshoreaquaculture projects are the two main growth sectors ofmarine emerging industries.The Chinese national carbon peak and carbon neutrallong-term plans bring new opportunities for thedevelopment of the offshore wind power industry.However, the cost of offshore wind power is much higherthan that of onshore wind power [43]. According to datafrom Bloomberg NEF, the cost of electricity per kilowatthour offshore in wind levels of major countries or regionsin the world will reduce significantly before 2026(Fig. 2). Reducing the design, construction, operation,and maintenance costs of offshore wind power under thepremise of ensuring structural safety is the key toimproving the competitiveness of offshore wind power.Large-scale implementation and Artificial Intelligence(AI) have become future development directions ofoffshore wind power. In the next 5 to 10 years, the singleunit capacity of offshore wind power will reach 15–20MW. A higher hub, heavier superstructure, and largerwind turbine load require higher technical standards foroffshore wind power support structures [44]. There willbe further challenges to traditional design concepts. Inaddition, with the continuous increase of the design pilediameter of offshore wind power foundations, thetraditional theory of pile-soil interaction is not applicable.There is still a lack of relevant theories for the behaviorof foundation and soil degradation under long-term cyclicloading [45]. For this reason, the integrated designmethod of integrated foundation-support structure-upperfan is a key technology to reduce structural redundancyand ensure structural safety. On the other hand, offshorewind energy development is moving from coastal shallowwater to offshore deep water. When the water depthexceeds 50 m, floating wind power technology will havebetter engineering economics. Norway, Japan, and othercountries have already carried out projects regarding thedemonstration and application of floating offshore windpower projects, but floating wind power technology inChina is still at the infant stage. The operating environment of floating offshore wind power is more complexand harsher than the coastal areas. Under the action ofenvironmental loads such as wind, waves and currents,there is a strong coupling between floating body movement, mooring deformation, tower elastic deformationand impeller rotation. Coupling analysis is still challenging for the design of offshore floating wind power[46,47]. With the aim to provide technical support for the
6Front. Struct. Civ. Eng.Fig. 2 Standardized cost analysis of global offshore wind levels (data source: Bloomberg NEF. Note that Chinese mainland and Franceinclude two lines, which represent two different estimates of cost officially released by each government).design, construction and safe operation of wind power,there is a critical need to develop multi-physics, multifloating bodies, and multi-scale coupling analysis anddesign methods for offshore floating wind power.Under the influence of overfishing, environmentalpollution, and decline in fishery resources, the world’sfisheries are changing from a development model basedon marine fishing to mariculture [48]. Maricultureengineering facilities are the basic guarantee for thedevelopment of the marine fishing industry, mainlyincluding marine pasture construction and maricultureplatform equipment. Traditional marine pasture construction and management are based on production experience,lacking systematic and scientific guidance. Modernmarine pasture construction has significant multidisciplinary characteristics, requiring comprehensiveconsideration of ecology and oceanography. It requirescharacteristics of standardization, information system,intelligence, systemization, etc., and relies on advancedtechnical support and management methods such asocean ranch online monitoring system [49]. At present,the site selection and planning technology of marineranches is not mature. It is necessary to comprehensivelyconsider the suitability and carrying capacity of theecological environment, to develop large-scale marineranching platforms, and to improve the habitat creationmode and behavior control technology for biologicalresources. Compared to nearshore mariculture, deepdistance sea areas have high-water exchange rate and lowpollutant content and have less effect on other marineactivities such as shipping. For this reason, floatingmarine mariculture platform equipment is developingdeep sea capability and showing a trend of large-scaleapplication of AI. Figure 3 shows the typical deep-seamariculture platform facilities designed and built in Chinaand elsewhere. Under deep sea conditions, larger waterdepths with stronger currents and waves bring newtechnical challenges to floating mariculture platforms[50,51]. Therefore, it is necessary to develop new deepsea mariculture equipment that adapts to complex seaconditions. At present, scholars at global level have madesome progress in the research of the hydrodynamiccharacteristics of large-scale breeding platforms [52,53]and breeding ships [54]. However, the equipment’s antiwind and wave performance and the research onstructural safety theory still have shortcomings. Thetechnologies of automatic bait throwing, pollutantdischarge, and catching are still not perfect. Theanchoring and positioning control technology, electricpropulsion and drive control technology are in urgentneed of breakthroughs in terms of informatization,digitization, and intelligence. In addition, the deep-seamariculture equipment is far from the shore and theenergy supply is difficult. A new energy supply supportsystem for the deep-sea mariculture platform has not beenfully established [55]. The potential impact of deep-seamariculture platforms on the ecological environmentremains unclear. The competitive use of oceans andnatural resources also needs in-depth study [56].As the development of emerging marine industriescontinues to boom, their integration exhibits promisingprospects. In the future, the combination of offshore windpower and offshore mariculture projects can share marinespace resources for joint construction, operation, andmaintenance. Offshore wind power can provide nearbypower supply for offshore mariculture facilities, reducingthe development and operation and maintenance costs.This will benefit the intelligent development of offshorewind power and marine mariculture [57]. Through theintegrated development of offshore wind power projectsand offshore mariculture projects, the intensive andefficient use of marine space resources can be realized, anew integrated marine development model can beformed, and other emerging marine industries will bepromoted to explore the path of combined and integrateddevelopment.
Huajun LI et al. Demands and challenges for construction of marine in-frastructures in China7Fig. 3 Typical deep-sea mariculture platform facilities: (a) deep-sea fishery Ocean Farm 1 [58]; (b) deep Blue No. 1 [59];(c) semisubmersible deep-sea fishery [60]; (d) deepwater mariculture ship Havfarm [61].3.5 Marine ecological crisis and engineeringcountermeasuresIn the early stage of marine development, people havetended to pay more attention to the short-term economicprofits, while ignoring the values and services of the marine ecosystem in the long term. Uncontrolled development and resource utilization depleted marine biologicalresources, exacerbated marine pollution, and degraded themarine ecological functions.Coastal and nearshore regions are the areas affected themost by human activities. Taking coastal wetlands as anexample, types of these in China include salt marshes,mangrove swamps, coral reefs, seagrass beds, etc. Withlarge-scale land reclamation and other coastal engineeringactivities, the total area of coastal wetlands has beendeclining year by year. The areas of temperate coastalwetlands and mangroves in China have decreasedconsiderably since the 1960s [62]. In response to thisissue, over the past five years, the Chinese governmenthas renovated and restored 1200 km of coastlines and23000 ha of coastal wetlands [63] by implementingvarious coastal ecology conservation plans such as the“Blue Bay” action. It is necessary for the government tomake continuous progress in promoting coastal conservation and restoration projects and ensuring their sustainable
Demands and challenges for construction of marine infrastructures in China Huajun LIa,b*, Yong LIUa,b, Bingchen LIANGa,b, Fushun LIUa,b, Guoxiang WUa, Junfeng DUa, Huimin HOUa, Aijun LIa, Luming SHIa a College of Engineering, Ocean University of China, Qingdao 266100, China b Shandong Province Key Laboratory of Ocean Engineering, Ocean University of China, Qingdao 266100, China
