Analysis of Water Seepage into Vacuum Anchor Subjected to Pull-Out Load

When constructing offshore facilities, their reliable fixation to the bottom surface is required. Many solutions for fixing to the bottom surface (weights and anchors) have been developed in the world. To solve this problem, it is proposed to use a vacuum anchor design. Conceptual diagrams of vacuum anchors installed in soft soils are presented. The purpose of the study is to substantiate the operability of vacuum anchors taking into account the influence of infiltration processes. To achieve this goal, mathematical techniques, search and analysis of Russian and international sources with data comparison were used. The position of the water seepage lines in permeable soil is determined by the electrohydrodynamic analogy method. Water seepage into the anchor subjected to a pull-out load was calculated; the seepage discharge of water was determined depending on the depth of the water body at the installation site, the thickness of the permeable soil layer and its permeability coefficient, and the geometric parameters of the vacuum anchors. The technology of driving vacuum anchors into soft bottom soil is described, the conditions of driving the anchor into the bottom soil and the conditions of it pulling out from the soil are calculated. It is established that vacuum anchors used for soft bottom soils have a significant retaining capacity with relatively small dimensions. At the same time, the thickness of the permeable layer of the bottom soil, exceeding five embedment lengths of the vacuum anchor into the bottom soil, practically does not affect the value of water seepage inside the vacuum anchor when subjected to a pull-out load. A reduction in costs is predicted when introducing vacuum anchors into the practice of marine construction.