Free-Fall Penetration Behaviors of A New Dynamically Installed Plate Anchor in Marine Clay

A new dynamically installed plate anchor, the Flying Wing Anchor~?, has been developed as a sustainable anchor concept for deep-water offshore wind turbines. The anchor is firstly installed by free-fall penetration and then followed by drag embedment. If the anchor is subjected to environmental loads, it dives deeper to mobilize a higher capacity. This study presents a series of free-fall penetration tests with model anchors in different weights to assess the anchor behavior during the free-fall penetration performance in one-layer soil with a constant shear strength profile. Anchor velocities and embedment depths were measured by a magnetometer. An energy-based model and a force-based model were calibrated against the test results of model anchors with different weights. Based on the calibrated force-based model, a series of design charts were developed to estimate the embedment depth of anchors in different sizes and with different impact velocities in various marine clays. The framework to plot design charts presented herein can be potentially applied to other dynamically installed anchors to predict embedment depth in engineering practice.

Dynamic Installation Behaviors of A New Hybrid Plate Anchor in Layered Marine Clay

Layered soil profiles create challenges for foundation installation and detrimentally affect the foundation performance.This research explored the free-fall penetration behavior of a new dynamically installed plate anchor,the Flying Wing Anchor?,in layered soil profiles.This new concept anchor combines the advantages of low-cost installation of torpedo piles and high efficiency of plate anchors.Anchor is initially installed through free-fall like a torpedo pile,and followed by drag embedment like a plate anchor.The methodology is to perform free-fall penetration tests with a model anchor in a variety of test beds containing marine clays with different profiles of undrained shear strength versus depth.A calibrated prediction model accounting for the effects of strain-rate and stiff layer produces results similar to those from the model test.The design curves were developed based on the calibrated analytical model,and are valuable to estimate the impact velocity thresholds of prototype anchor to penetrate through stiff layers.The free-fall penetration tests indicated that the penetration ability of FWA?increases with the increased impact velocity.This new dynamically embedded plate anchor can penetrate through the stiff layers that would cause problems for the conventional plate anchor,such as the drag embedded anchor,plowing on the top of stiff layer instead of breaking into it.Therefore,the new dynamically embedded plate anchor can provide a possible solution for layered soil profiles in deep water.