Submarine Pipeline Routing Risk Quantitative Analysis

Transactions of Tianjin UniversityVol.10 No. 4Dec.2004Submarine Pipeline Routing Risk Quantitative AnalysisXUHui(徐慧) ,YULi( 于莉) ,HU Yun-chang(胡云昌y ,WANG Jin-ying(王金英尸( 1. School of Civil Engineering ,Tianjin University ,Tianjin 300072 ,China ;2. Marine 0il Engineering Incorporated Company , Tianjn 300450 ,China )Abstract :A new method for submarine pipeline routing risk quantitative analysis was provided , and the studywas developed from qualitative analysis to quantitative analysis. The characteristics of the potential risk of thesubmarine pipeline system were considered , and grey-mode identification theory was used. The study processwas composed of three parts : establishing the indexes system of routing risk quantitative analysis , establishingthe model of grey-mode identification for routing risk quantitative analysis , and establishing the standard ofmode identification result. It is shown that this model can directly and concisely rllcet the hazard degree of therouting through computing example , and prepares the routing selection for the future.Keywords routing risk quantitative analysis ,relational difference degree igrey subordination degree igrey-modeidentification theoryArticle ID :1006- 4982( 2004 )04-0304-06It is one of the most important steps at the beginning 1 Indexes system of the routing risk quan-of the design of submarine pipelines to evaluate the risk oftitative analysis of the submarine pipelinerouting project that has been defined. Since the potentialsystemrisk of the submarine pipeline system has complex , ran-According to engineering practice , the hazards thatdom ,fuzzy and information-imperfection characteristics ,ainfluence the submarine pipeline system can be classifiedmodel of grey-mode identification for submarine pipelinerouting risk quantitative analysis was provided. The entireinto three groups : engineering geology conditions , oceananalysis was composed of three procedures :1 ) establishenvironmental conditions and ocean exploitation conditionsthe indexes system of routing risk quantitative analysis ;2 )around pipeline routes. The concrete index items of eachestablish the model of grey-mode identification for routingpart are shown as follows :risk quantitative analysis ; 3 ) establish the standard of1 )The index items evaluating the engineering geologymode identification result '1.conditions in routes area(2( see Fig. 1 ).Engineering geology conditionsAverage gradientStability capacityExtent of flling up | Buried depth ofBuried depthEarthquakeof bottom bedof soil in bottomor washing outshallow gasof bedrockfrequencyintensitybedNotes 1 ) Stability capacity of soil in botto bed varies according to the soil quality type. The type of sandy soil and clay can be classifiedby friction angle and shear modulus respectively 31.2 ) Earthquake intensity is lassified by the index taking 10% as exceeding中国煤化工Fig. 1 Indexes system of engineering:TYHCNM HG米Accepted date 2004- 06- 14.XU Hui , borm in 1957 , female , M ,associate Prof.E-mail : tjuxuhui@ 263. netXU Hui et al Submarine Pipeline Routing Risk Quantitative Analysis2 ) The index items evaluating the ocean environmen- and exploitation activity situation.tal conditions-4-Ocean establishments are mostly submarine cablesThe ocean environmental conditions can be classified and pipelines that have been established or are planned tointo three groups : weather factor , marine hydrology , and be established in routes area. Ocean exploitation activitiescorrosion environment of seawater and marine bed. The are economic activities , such as fishery and aquacultureconcrete indexes are shown in Fig. 2.traffic activities on the sea such as sea-route and anchorage3 ) The index items evaluating ocean establishments ground , military activities ,and so on( see Fig.3 ).Weather| Average air temperaturefactorsAverage wind speedl Extreme tide rangeL Extreme current velocity in ebb and flowl Defection angle between the current drection and route strike _MarineMaximum of wave heighthydrologyconditionsDeflection angle between the wave direction and route strikeThickness of fast iceOceanThickness of drift iceenvironmentalVelocity of drift iceOxygen level dissolved in bottom seawaterSaturation solubility of oxygen in bottom seawaterAcidity and alkalinity of sediment(pH value)Ratio of Fex and Fe”in bottom beld(e*/Fe*)CorrosionVariation range of redox potential of sedimentconditions ofContent of organic matter in bottorm bedseawater andmarinee bedContent of sulphides in bottorm bedBuried depth of sulphate reducing bacteria in bottom bedMonthly average weight of ataching organismDensity of boring organismFig.2 Indexes system of ocean environmental conditionsIn the proces of pipeline routing analysis , the factor index risk rank of each section'5-8].set can be added or reduced properly under the guidance of 2. 1 Index evaluation matrix , index standard matrixexperts , according to the particular case of routing.and standardizationSuppose a routing of n evaluation pipeline sections2Submarine pipeline routing risk analysis and the number of risk identification index of each evalua-model based on grey-mode identification tion section is m , so index evaluation matrix can be ob-theorytained as X=( xy)mxn ,wherexi( i=1 2.. mj=1 2... n )is the initial value of the ith index in the jth evalua-tion sect中国煤化工from m to C kinds ofIn the process of routing risk analysis , risk quantita-standardIY片C N MH Gard matrix can be ob-tive analysis can be performed in the form of subsection.tained asS=( Sa )mx( t=1 2 p.. C )where C can be se-After the risk rank of each section is obtained , the mostdangerous risk index can be defined through the taxis forlected according to practical conditions on condition that2≤C≤m.一305一Transactions of Tianjin UniversityVol. 10 No.4 2004Horizontal distance to established cables and pipelinesSubmarineestablishmentsVertical distance to established cables and pipelines when they are crossedthat have beenestablished orHorizontal distance to cables and pipelines that are planned to be establishedare going tobe establishedVertical distance to cables and pipelines that are planned to be established when they are crossedSail density of fishing ships_Sinking probability for crash between fishing shipsGrounding pobabiliy for fishing shipsEconomicOceanactivities suchAnchoring probability for fishing shipsexploitationas fishery andactivitiesaquacultureAnchor weight of fishing shipsAnchor holding force of fishing shipsEmbedded depth in the earth of fishing ships ' anchorEmbedded depth in the earth of the pile which is used to put up fishing netSail density of carrying shipsSinking probability for crash between carrying shipsGrounding probability for carrying shipsMilitaryAnchoring probability for carrying shipsAnchor weight of carrying shipsAnchor holding force of carrying shipsEmbedded depth in the earth of carrying ships' anchorFig. 3 Index items evaluating ocean establishment and exploitation activitiesIn order to eliminate the influence of index matrix di-Use B=( b;)mxc R=( rj )m xn to denote standardizedmension , indexes should be changed to non-dimension index standard matrix and evaluation matrix.ones : the standard non-dimension values of the first level2.2 Computation of relational degreeand the C level are 0 ,1 , respectively ; other levels are allFor the influences on swatch caused by each judge in-between 0 and 1. The risk evaluation indexes of submarine dex are reflected in classification standard , of which varia-pipeline routing can be classified into two groups :tion extent is different , the weight of each index can be .maximum type index- -if value is bigger , level is computed using the following formulas :higher ;maximum type indexminimum type index- -if value is smaller , level ishigher.。一信点心Non-dimension standardization expressions of maxi-minimum type indexmum type index :0a =-(点↓)(3)xi≤siiry={(xg-sa )(sc-sa) sa m;,2u;=1fuzzy mathematics , the grey subordination degree Uj; in thisand the full form of grey-mode identification theory modelpaper should meet the following conditions :of Eq.( 11 )is2u,=1,j=12.. n;(1， t=m,=M;2up >0,1=12. C( 8)|12 {[1- Ewξ(r; b,)]/中国煤化工(13)In order to solve the optimum subjection degree of e-MHCNMHG(I, b:)]}'，valuation section j to level t , construct the target functionas follows : the square sum of weighted relational differencem;≤l≤M;degree of the entire swatch to each level standard mode is0，t>M;ort15( where KP4.04- 4. 66 )Buried depth of shallow gas/m4525.3Extent of flling up or washing out/ m0.2- -0.3-0.4- -0.80.6-1.0Earthquake frequeney/%Earthquake intensity/ degree4.755. 256.7Note :The measured clay content in silty clay in this example is 50%一60% ;silt content is 35%- -50%。 Silt content in clayey silt is 55%- 65% ; clay contentis35%- 45% When there is no bedrock , consider its buried depth infinite. KP- -key point is used to denote routing strike in Tab. 3.According to Eq.( 14 ) , compute the eigenvalues of more accordant to fact. .grade variable of these three evaluation sections :3 ) Weight of index was determined according to vari-H,=(1.96 1.09 2.02) (j=1 2 3)able extent of classification standard in this paper. If thereAccording to Tab. 1 ,judge that the risk ranks of these were experts groups , weight of index could be determinedthree pipeline sections in the aspect of engineering geology through qualitative comparison between each two by usingconditions are 2 ,1 ,2 respectively , and then compare the fuzzy theory of excellent selection.risk degrees of these three pipeline sections according tReferencestheir risk ranks and their order is bank slope section under-water , tidal flat and tidal chunnel section in turn from high [1 ] Pranesh M R ,Johnson A s. Submarine pipeline routing software com-puters and structures[ R ] New Delhi ,1993.to low. In general ,it is safe. So the selection of routing in[2] Huang Yiguang. Elementary Discuss of Submarine 0Oil and Gas Pipe-this pipeline landing project is reasonable.lines Routing Engineering Geology Conditions Evaluation[ M ] SanyaChina : Nan Hai Geology Research ,2000.4 Conclusions[3 ] Det Norske Veritas. Recommended Practice DNV-RP-F105 , March2002( Norway ).1 )A model of grey-mode identification for submarine[4] Liu Nianfeng , Lao Wei , Guo Jixiao et al. Mulistage grey connectiondistinguish model application for comprehensive evaluation of ecologi-pipeline routing risk quantitative analysis was established. .cal environmental qualit[ J ] Environmental Science and Technology.This model overcomes the shortcomings of homogenized1999(3):24- -27( in Chinese ).tendency of evaluation result and low distinguishing rate in[5] Li Zhibin ,Zheng Chengde. Grey-mode identifcation theory and modelfor landslide and debris flow risk degred[ J ] Systems Engineering-the common grey interrelation analysis method. And theTheory & Practice 2000 20( 5 ):128- -132( in Chinese ).evaluation results are continuous and comparable. Results[6] Shi Xiaoxin , Xia Jun. Grey-mode identifcation model for water envi-from example computation show that this model can con-ronmental quality assessment and its application[ J ] China Environ-cisely and directly reflect the hazard degree of the routingmental Science ,1997 ,17( 2 )127- -130( in Chinese ).[7] Chen Shouyu. Engineering Fuzy Set Theory and Apicatior[ M ]. Bei-system.jing : National Defence Industry Press ,1998( in Chinese ).2 ) Result from this model was optimum grey subordi-[8] Schol of Civil Engnering , Tianjin University. Research on Subma-nation degree , and in this model eigenvalue of grade varia-rine Pipelines System Safe Risk Evaluation and Management Systemble was taken as judge index , so all the information were .[ R ]. Tianjin , China :Tianjin University ,2003 5.ully used , which made the judge more exact and the result中国煤化工MHCNM HG一309一