The helical piles have been being treated as a kind of novel foundation for offshore wind turbines recently, due their fast installation, high uplift capacity, convenience for recycling, and other advantages. The recycling of the helical pile especially will reduce the cost significantly and protect the environment as much as possible. However, the research for this area is basically in infancy and there is no reference for predicting the recycling torque of a helical pile in sand. In order to predict the recycling torque of single-plate helical piles in dense sand: a theoretical model, which was inspired by the way to predict the installation torque of single-plate helical pile in sand, was developed, and a series of single gravity model tests were conducted to verify that theoretical model. The theoretical model can predict the recycling torque of single-plate helical pile considering the influences of the size of helix and the vertical force on the shaft. This model fills in the blank of predicting the recycling torque of a single-plate helical pile in sand and it is also useful guidance for the choice of suitable recycling equipment.
Helical piles with small sizes are widely used in traditional civil engineering infrastructure application, especially in onshore electrical power industry. The floating offshore wind power industry has taken an interest in helical piles because of their rapid installation and ability to support immediate loading. Compared with onshore structures, wind power structures suffer larger external load and it becomes necessary to increase the overall size of helical piles, leading to considerable load capacity provided by the shaft, which is typically neglected for a light structure. In this paper, the undrained uplift capacity of helical piles was studied using finite-element limit analysis. The analysis explored various diameter ratios of the shaft to the plate and embedment depths, as well as different interface conditions. The local bearing capacity on the plate was also explored for attached and vented interface conditions. The failure mechanisms of a helical pile were presented to explain the mutual influence between plate anchor and shaft on the uplift capacity. Algebraic expressions for the uplift capacity of a helical pile were proposed. Engineers may use these expressions to improve the accuracy of their estimates for the uplift capacity of helical piles.
Offshore pipelines provide the main link between offshore oil and gas fields and hydrocarbon development onshore. Due to their economical installation, untrenched pipelines laid “on-bottom” are finding increased popularity over other types of offshore pipelines. However, the stability of untrenched pipeline design remains the subject of criticism. In many cases around the world, severe loading conditions, such as those during hurricanes, result in severe pipeline damage and disruption of oil and gas supply. In on-bottom pipeline stability analysis, hydrodynamic loads are applied to the pipe structure. The pipe passes these loads onto the supporting soil along its length. A variety of parameters need to be defined to model this loading scenario and to reflect the complicated interaction between the hydrodynamic load, pipe structure and the supporting soil. Moreover, there are uncertainties regarding the input values of these parameters, as any difference in these parameter values will result in a considerable difference in the final pipeline stability result (though the sensitivity to any differences is not well studied). In this study of the offshore pipeline stability, the hydrodynamic loads are estimated using Fourier analysis, which is currently the best practice in hydrodynamic modeling. The pipe-soil interaction is simulated with a force-resultant model, which is derived from a plasticity framework and is based on the results of centrifuge test calibration. The pipeline is modeled using an integrated numerical modeling tool developed by implementing the hydrodynamic load model and force-resultant model codes in the finite element package ABAQUS. Use of the integrated modeling tool allows for the coupling effect of the hydrodynamic-pipe-soil interaction to be accounted for, with the added ability to modify the applied hydrodynamic loads due to pipe movements during the analysis. The main aims of this paper are to demonstrate methods to estimate the probability of exceeding pipeline stability and quantify the importance of the on-bottom pipeline statistical analysis and the sensitivity of the parameters included in the pipeline stability design. After first describing the integrated model and providing an illustrative example of its use these aims are achieved by i) performing probabilistic analysis for a typical pipeline case and investigating the probability of exceeding pipeline stability under different maximum pipeline displacement values; and ii) developing a sensitivity analysis of the input parameters included in the on-bottom pipeline stability and ranking these parameters according to their sensitivity to the pipeline stability design.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.