Continuous burial assessment of cables:
A STATE-OF-PRACTICE Burial assessment should address a number of aspects, such as: 1. can the cable be buried and if so, to what depth? 2. what is the most appropriate burial method (e.g. ploughing, jetting, trenching, others)? 3. what is the anticipated performance of the recommended burial method (e.g. advancement speed)? 4. in case of ploughing, which is the most commonly used method, what are the expected tow forces? How are these forces affected by the ploughing speed? 5. is the burial tool stable on the seabed? 6. what is the anticipated wear of the burial equipment?
To provide the appropriate answers, burial assessment surveys of cables require specific data • water depth and seabed topography, • anomalies on and in the seabed (e.g. geohazards, existing pipelines or cables, other obstructions), • differentiation of strata with significantly different geotechnical properties affecting burial operations, • geotechnical parameters . Information provided by standard route selection geophysical surveys - aimed at providing the first two sets of data - is insufficient to address all burial assessment issues. Different approaches have been proposed and implemented in the last decades ( Plough Assessment Survey, CPT only BAS) but none of them has proved to be fully satisfactory. 28
Burial analysis is conceptually a foundation problem. An efficient and cost effective burial assessment survey is a threefold challenge: 1. geotechnical tools shall be available to obtain the required soil data at preselected locations, operational in least 2000m depth and easy to operate; 2. burial analysis methods based on the geotechnical information obtained from these tools shall be available (or developed) and calibrated on actual burial data; 3. burial predictions shall be made continuously all along the route i.e. there is a need for a tool to interpolate geotechnical parameters and ploughing analyses in between the sampling/ testing locations.