This paper employs finite-element analysis to investigate the performance ofmud line cellars (MLC) in various stratigraphic settings representative for theArctic offshore environment. Numerical results addressing the stability of mudline cellars excavated in sand-prone Arctic marine sediments revealed apotential flow-like mode of failure associated with a high degree of materialdisruption within the failure wedge. On the other hand, the computed potentialfailure mechanism of a mud line cellar excavated in clay-prone Arctic marinesediments is characterized by a sliding block mode of deformation. For theconsidered geotechnical properties of unfrozen Arctic marine sediments, free-standing sand mud line cellars are prone to instability thus requiringadditional lateral support, whereas free-standing clay mud line cellars appearto be stable. The analysis results for a free-standing mud line cellarexcavated in clay with adjacent surcharge at seafloor indicate a progressiveincrease in the size of the potential failure wedge controlling the stabilityof the MLC wall with increasing surcharge horizontal distance relative to themud line cellar location. For surcharge horizontal distances exceeding aspecific threshold, the dominant potential failure mechanism of theMLC-surcharge system in clay undergoes transition from a fully-developedfailure wedge localized at the face of the excavation wall to a more generaltype of bearing capacity failure mechanism developed underneath and in theimmediate vicinity of the loading area of the surcharge that has no significantinfluence on the stability of the MLC wall. Numerical investigations addressingthe performance of a caisson-supported mud line cellar in sand with adjacentsurcharge revealed that the caisson may experience wall bending in combinationwith rigid body rotation due to surcharge-induced lateral soil movements in thevicinity of the mud line cellar.
Mud line cellars are cylindrical excavations created below the seafloor inthe Arctic offshore environment in order to protect exploration and productionwells against potential ice gouging hazards. A mud line cellar allows for thewellhead assembly and blowout preventer to be installed below the seafloor atdepths greater than the anticipated ice-scour depth, therefore, stability ofsuch excavations is crucial for safe well drilling and completionoperations.