Relationship between installation torque and axial capacities of helical piles in cohesionless soils

2015 ◽  
Vol 52 (6) ◽  
pp. 747-759 ◽  
Author(s):  
Mohammed Sakr
Keyword(s):  
Transmission Lines ◽  
Oil And Gas ◽  
Load Path ◽  
Cohesionless Soils ◽  
Groundwater Levels ◽  
Axial Capacity ◽  
Pile Installation ◽  
Pile Shaft ◽  
Torsional Resistance ◽  
Helical Piles

With the rapid growth of the helical piling industry for oil and gas projects and transmission lines, reliable installation torque estimates and measurements become crucial. This paper presents a theoretical model developed to estimate the torsional resistance of cohesionless soils to helical pile installation. The theoretical torque model was verified using installation records collected from different sites. The paper also highlights factors that affect helical pile installation, including soil properties, fluctuation in groundwater levels, shape of pile shaft, pile geometry, and method of helical pile installation. The proposed torsional resistance model was then used to establish the traditional torque factors to proportionally correlate the axial capacity of helical pile and the installation torque. The results of the study indicated that the torque factor is a function of the load path (i.e., tension or compression). Therefore, torque factors in compression and tension, Kc and Kt, respectively, were formulated and presented in the paper.

scholarly journals Review of torque models for offshore helical piles

2020 ◽  
Vol 205 ◽  
pp. 12007
Author(s):  
Giovanni Spagnoli ◽  
Cristina de Hollanda Cavalcanti Tsuha
Keyword(s):  
Strong Influence ◽  
Friction Angle ◽  
Soil Conditions ◽  
Uplift Capacity ◽  
Pile Installation ◽  
Pile Shaft ◽  
Geometrical Features ◽  
Helical Piles ◽  
Installation Depth ◽  
Torque Values

Helical (or screw) piles, sometimes defined as anchors, are a piled system consisting of one or multiple helices welded along the shaft. Piles are installed by applying a torque to the shaft. The pile is rotated into the soil and the rate of advancement should be an amount equal to the pitch for each rotation in order to minimize the disturbance of the original soil. Torque is maybe the most important parameter to be assessed during pile installation. In fact, torque and uplift capacity are directly proportional. Generally, torque depends on the soil conditions and on the geometrical features of the pile. Torque increases with sand density, installation depth, friction angle of sand, pile shaft and helix diameters. The geometry of the pile has a strong influence on the torque, the larger the helix-to-shaft ratio is, the larger the torque will be. In offshore applications helical piles are being considered as a valid alternative. However, one of the issues is still related to the assessment of the installation torque values. Several torque models have been considered and critical evaluated. Some simple comparisons among selected torque models have been also done and discussed.

Preventing Girth Weld Failure in Pipelines: Measurement of Loads and Application of Assessment Methods

2020 ◽  
Author(s):  
Andy Young ◽  
Robert M. Andrews
Keyword(s):  
Transmission Lines ◽  
Oil And Gas ◽  
Large Diameter ◽  
Ground Movement ◽  
External Loading ◽  
Key Factors ◽  
Axial Loads ◽  
Contributing Factors ◽  
Increased Risk ◽  
Girth Welds

Abstract Pipeline failures from circumferential cracking at girth welds continues to affect large diameter oil and gas transmission lines, even for modern lines constructed this century. The key factors that contribute to the failure at girth welds are the dimensions of defects present, the material properties of the pipe and weldments, and the presence of loading that drives crack growth. The mechanisms of failure are well understood, but identifying and measuring the contributing factors can be a challenge. Locating girth welds that are subject to elevated loads will enable operators to focus on sections with an increased threat of failure. In this paper, we consider each of the key factors, how these are identified and defined, and the uncertainties in the measurement process. Specific attention is applied to the presence and quantification of loads and how these influence the potential for failure. This includes sources of active external loading due to ground movement, for example, or loads generated in the pipeline from the construction process. Loads can also be quantified by measuring bending strain from inline inspection inertial measurement units. A more complete picture of pipeline loading can be established by integrating a structural analysis that accounts for the direction of pipeline movement and the presence of axial loads. The relationship between assessing pipeline integrity from ground movement — typically with strainbased methods — and establishing whether the defect can survive the load is explored. The relative contribution of bending and axial loads in the failure of defects is considered. The outcome of the study will assist pipeline operators in prioritising actions that enable the quantification of the all the key parameters. The resultant analysis will provide guidance on the girth welds that have an increased risk of failure and this will enable protective actions to be defined and scheduled accordingly.

scholarly journals Some aspects of design and application of inertial dampers

2018 ◽  
Vol 178 ◽  
pp. 06010 ◽  
Author(s):  
Maciej Dutkiewicz ◽  
Irena Gołębiowska ◽  
Ivan Shatskyi ◽  
Vasyl Shopa ◽  
Andrii Velychkovych
Keyword(s):  
Transmission Lines ◽  
Oil And Gas ◽  
Oil And Gas Industry ◽  
Gas Industry ◽  
High Rise ◽  
Overhead Transmission Lines ◽  
Common Effect ◽  
Vibration Impact ◽  
Passive Dampers ◽  
Particle Dampers

Over the last years, there has been intensive development of technologies applied to protect structures such as overhead transmission lines, chimneys, high rise buildings from excessive dynamic effects leading to their damage or destruction. In the paper special attention is put on the system of passive dampers applied to overhead transmission lines and dampers used in oil and gas industry. The efficiency of the aeolian damper is presented. The constructions of weighted drill pipes with vibration-impact particle dampers designed to absorb the energy of longitudinal and twisting oscillations of the drill tool are described. The advantage of a multi-container absorber is substantiated. The application aspects of the inertial dampers developed by the authors are combined using a common effect based on the antiresonance phenomenon.

scholarly journals Behaviour of Single and Group Helical Piles in Sands from Model Experiments

2019 ◽  
Vol 278 ◽  
pp. 03007
Author(s):  
Jongho Bak ◽  
Byung-hyun Choi ◽  
Junwon Lee ◽  
Jonghwan Bae ◽  
Kicheol Lee ◽  
...  
Keyword(s):  
Rotation Speed ◽  
Axial Loading ◽  
Complete Removal ◽  
Drilled Shafts ◽  
Load Test ◽  
Oil Sand ◽  
Driven Piles ◽  
Pile Installation ◽  
Helical Piles ◽  
Pile Load Tests

Mainly used foundations of oil sand plants are drilled shafts or driven piles. As environmental regulations become increasingly strict, complete removal of the foundation is becoming more important during the step of plant dismantling. However, it is difficult to remove completely drilled shafts or driven piles which are deeply installed to obtain more bearing capacity. Helical piles can be easily removed and recycled after use. This study analyses the behaviour of single and group helical piles in sands. For single helical piles, pile load tests of helical piles were conducted varying helix spacing, rotation speed and weight of axial loading during pile installation. The single pile tests determined the optimal helix spacing, rotation speed, weight of axial loading during pile installation. And then, pile load test of group helical piles was performed varying pile spacing from the centre place of upper connector based on the optimal installation conditions.

scholarly journals Time-lapsed shear-wave velocity (Vs) tomographic images and stress in sand surrounding displacement pile during setup

2020 ◽  
Vol 57 (5) ◽  
pp. 635-649
Author(s):  
Yuxin Wu ◽  
Jun Kang Chow ◽  
Jimmy Wu ◽  
Yu-Hsing Wang
Keyword(s):  
Shear Wave ◽  
Wave Velocity ◽  
Shear Wave Velocity ◽  
Pressure Sensors ◽  
Load Test ◽  
Pile Setup ◽  
Aging Rate ◽  
Pile Installation ◽  
Pile Shaft ◽  
Spatio Temporal

This study reports model pile tests designed to characterize the underlying mechanisms of driven pile setup in dry sand by means of stress measurement with the tactile pressure sensors and spatio-temporal, shear-wave velocity (Vs) distributions using an automated high-speed tomographic imaging system. The pile-load test results demonstrate a distinct increase in the pile shaft resistance after pile setup. The measured stress and Vs in the soil surrounding the pile suggest the increase in the radial effective stress during pile loading [Formula: see text], as a result of the aging-induced stiffness increase, is the dominant mechanism of pile setup. The spatio-temporal evolution of Vs distributions reveals that during initial aging (before pile installation), Vs is similar at any distance to the pile shaft and exhibits a similar aging rate S0 in terms of stiffness increases. After pile installation, the soil exhibits a higher aging rate S1. In addition, the ratio S1/S0 decreases with increasing distance from the pile shaft. A lower initial Vs and a higher aging rate S1 are also observed for the measurements at the three sensing layers of different depths, suggesting that more soils disturbed by pile installation tend to recover at a relative higher aging rate.

scholarly journals Wind tunnel demonstration of galloping mitigation with a purely nonlinear energy sink

2020 ◽  
Author(s):  
Michael Makram Selwanis ◽  
Guilherme Rosa Franzini ◽  
Cédric Béguin ◽  
Frederick Gosselin
Keyword(s):  
Transmission Lines ◽  
Oil And Gas ◽  
Nonlinear Energy Sink ◽  
Oil And Gas Industry ◽  
Low Flow ◽  
Radial Clearance ◽  
Small Range ◽  
Flow Speeds ◽  
Energy Sink ◽  
Nonlinear Energy

Galloping is a critical type of flow-induced vibration (FIV) arising on power transmission lines, high rise buildings, pipe and cables bundles in the oil and gas industry. In this paper, we present a purely nonlinear energy sink (NES) that mitigates the galloping of a square prism. The NES is composed of a ball rotating freely in a circular track attached to the prism. The ball’s dynamics is coupled to that of the prism in a purely nonlinear way by inertia. We experimentally assess how this simple NES reduces the prism vibration by comparing the prism amplitude responses with and without the NES. A supplementary video presents these experiments, during which the NES ball exhibits different dynamics in three regimes; oscillatory, intermittent, and rotational. We characterize the ball behaviour and its effect on the prism response in each regime. The oscillatory regime appears at low flow speeds at which both the prism and the ball oscillate with small amplitude. The intermittent regime represents a transition mode within a small range of flow speeds and corresponds to a small jump in the vibration amplitude of the prism. The rotational regime appears at higher flow speeds, where the ball oscillates with relatively high angular speeds resulting in a strong modulated response of the prism. The design of the NES allows to easily vary its track dimensions to use a ball of different sizes and masses. Accordingly, we demonstrate the influence of the main NES parameters, which are the ball mass, NES track radius, ball friction, and radial clearance between NES track walls and the rotating ball, on both the prism response and the ball behaviour. The NES we present is directly amenable to mitigate other types of FIV.

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