conference & convention enabling the next generation of networks & services BURIAL ASSESSMENT AND SUCCESSFUL CABLE BURIAL: OLD TOPIC, NEW LESSONS OLD TOPIC, NEW LESSONS R. Rapp, C. Carobene, F. Cuccio Tyco Electronics Subsea Communications 1
conference & convention enabling the next generation of networks & services Presenter Profile Dr. Rapp is the Director of Cable Engineering and Technology at TE SubCom in Morristown, NJ, where he manages the Desk Top Study, Route Survey and Engineering, Marine Liaison, and Geographical Information Systems (GIS) groups. Collectively the organization engineers undersea telecommunications systems Place around the world. Ron has worked in the marine field for over 30 years with a number of companies including AT&T Bell picture Laboratories, Lucent Technologies, and Chevron. He holds a BS here degree in Mechanical Engineering from the Pennsylvania State University and a Ph.D. in Ocean Engineering from the University and a Ph.D. in Ocean Engineering from the Massachusetts Institute of Technology where he did research in deep water wave breaking. Dr. Ronald J. Rapp Director, Cable Engineering & Technology TE SubCom (Formerly Tyco Telecom) Email: rrapp@subcom.com Tel: (+1) 973-656-8215 Mobile Tel: (+1) 908-930-1146 2
Cable Faults and Threats conference & convention enabling the next generation of networks & services 70% All External Aggression Faults (%) 60% Tyco Data 04-06 50% ASN Data 05-06 40% 30% 20% 10% 0% Abrasion Dredge Geological Crushing Fishing Anchors Other M. Kordahi, S. Shapiro, G. Lucas, “Trends in submarine Cable System Faults,” SubOptic 2007 M. Kordahi, S. Shapiro, G. Lucas, “Trends in submarine Cable System Faults,” SubOptic 2007 Fishing and anchoring pose the greatest risk to cable security. Cable burial remains the most effective and economical method of protection against these threats. 3
conference & convention enabling the next generation of networks & services Ensuring Cable Security Requires consideration over the full project cycle! Desktop Study Route Selection Survey, Seabed Assessment, Route Refinement Burial Feasibility Study Burial Operations Cable Awareness Program This paper focuses on understanding the full set of conditions that impact plow operations and performance and on the marine survey and analysis to assess these conditions and the burial feasibility. This remains crucial to installing a reliable system and has significant commercial implications. 4
conference & convention enabling the next generation of networks & services Background P. Mole, J. Featherstone, S. Winter, “Cable Protection – 1997 Introduction of Burial Solutions Through New Installation and Burial Approaches,” SubOptic, 1997, San Francisco, USA. Protection Index (BPI). Burial depth required to protect cable P.G. Allan, “Selecting Appropriate Cable Burial Depths – A is a function of soil stiffness. Methodology ,”IBC Conference on Submarine Communications, Cannes, 1998 Threat penetration R. Hoshina, J. Featherstone, “Improvements in Submarine depths and protection Cable Protection,” SubOptic 2001, Kyoto, Japan methods M. Jonkergouw, “Industry Developments in Burial M. Jonkergouw, “Industry Developments in Burial Assessment Surveying (BAS),” SubOptic 2001, Kyoto, Review of invasive BAS Japan tools, E-BAS, C-BASS R. Rapp, R. Munier, I. Gaitch, G. Lucas, T. Kuwabara, “Marine Installation Operations: Expectations, Accuracy of Burial Depth Specifications, Value and Performance,” SubOptic 2004, Monaco. Measurements R. Rapp, J. Mangal, R. Munoz, “Accuracy of Cable Burial Depth Measurements: A Review of the Issues,” Limitation of E-BAS in International Cable Protection Committee (ICPC) shortened project cycles Plenary 2002, Naples, FL, USA. 2007 M. Jonkergouw, “Is BAS Still Necessary, and if so, Where and How?,” SubOptic 2007, Baltimore, USA. 5
conference & convention enabling the next generation of networks & services Focus Is Now on Plow Operability Previous Now Use of complete suite of survey tools to fully characterize the seabed BAS tools to measure shear strength Focus on Plow Operability and Operability and maximizing time Focus has been on bottom on soil stiffness, depth of burial, burial protection Rocky variable seabed index (BPI) 1.5 m to 3 m plows with high pull capability Relatively flat homogeneous seabed 0.6 m to 1.5 m plows with moderate pull capability 6
conference & convention enabling the next generation of networks & services Survey Tools and Techniques SideScan Sonar SideScan Sonar Sub Bottom Profiler Sub Bottom Profiler Multibeam Echosounder bathymetric mapping Gravity Core Cone Penetrometer (CPT) Burial assessment cannot rely on any one tool or single piece of survey gear; it must be based on an integrated analysis of all data. 7
conference & convention enabling the next generation of networks & services Survey Data Interpretation WNW E S E Centre P osition 13° 5 5’28” 78 ° 09 ’30” Depth 377m V ertical scale lines: 250m Horizontal scale lines: 10m V ertical exaggeration: approx 25 times Sub Bottom Profiles Seabed Shear Strength to 3 m Multibeam swath depicting pipeline Crossings south of Singapore Core Samples Experienced and knowledgeable geologists provide accurate data interpretation to engineer best burial routes. Plow operations considered so to maximize tool Side Scan Sonar Image – Coral Heads performance, improve cable burial and thus enhance cable protection. 8
conference & convention enabling the next generation of networks & services Burial Feasibility Study (BFS) Key Elements of the BFS Burial Category: Example Only A: Cable burial to a target cover depth of 0.8 –1.0 m; • Seabed description Deeper burial B: Cable burial to a target cover depth greater than 0.4 m but less than 0.8 m; may be • Core and CPT C: Cable burial to a target cover depth of less than 0.4 m; required in D: Risk of uncontrolled cable burial to a cover depth of greater than 0.8 m; penetration depth many cases E: Cable burial to a target cover depth of 1.5 m in water depths of 10-20 m; • Hazards such as slopes, F: Cable burial to a target cover depth of 3 m in water depths of less than 10 m; G: Cable burial to a target cover depth of 3 m. rock, boulders, coral, sand waves, soft Risk Category: 1: No identified risk of damage to the burial equipment due to seabed conditions; sediment, pock marks 2: Possible risk of damage to burial equipment due to seabed conditions. Scale of possible damage to be • Cable or pipeline repairable on the installation vessel using shipboard equipment; 3: High risk of damage to the burial equipment due to seabed conditions. Scale of possible damage in crossings crossings excess of category 2. excess of category 2. • Currents that may affect plow or ROV deployment or operations Results of the integrated survey and analyses form the Burial Feasibility Study BFS is a guideline to predict burial likelihood and plow risk along the route Where seabed not conducive to burial, consider uparmor only if warranted by risk of external aggression 9
Cable Burial Tools conference & convention enabling the next generation of networks & services Towed cable plows remain the industry standard for cable burial. Improved capability allow deeper burial and in more challenging seabed. The burial will be dictated by plow operations and reasonable plow operations and reasonable endeavors guidelines. MD3 – 3 m Plow Sea Stallion 3 m Plow Sea Plow 7 - 1.5 m Plow ROV for Jet burial New burial tools are more capable and less sensitive to soil stiffness; seabed bathymetry and features are more critical to performance. 10
Case Studies conference & convention enabling the next generation of networks & services Selected SubCom Systems Installed over the past 3 years Recommendations and lessons learned were based on projects representing a range of seabed conditions; recent burial assessments were compared to the actual success of cable burial. 11
Results and Correlation conference & convention enabling the next generation of networks & services Integrated analysis of seabed comprising sidescan sonar, multibeam echosounder, sub- bottom profiler data and later ROV inspection ROV inspection Goal is to obtain a strong correlation between the survey results, describing the seabed composition and features, and the actual conditions ultimately encountered by the burial tools (plow and ROV). 12
Results and Correlation conference & convention enabling the next generation of networks & services Plowing is not always recommended. Surface laid cable is well conforming to the seabed in areas not suitable for plowing. 13
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