Review of torque models for offshore helical piles

Abstract

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.

Nghiên cứu thiết kế thiết bị thi công hạ cọc ống thép có cánh ở mũi và thành cọc phù hợp với điều kiện Việt Nam

“…Trong đó, phổ biến và có độ chính xác cao được áp dụng rộng dãi hiện nay là mô hình xác định mô men hạ cọc ống thép dựa vào sức chịu tải nén giới hạn theo đất nền của cọc. Theo các nghiên cứu[13][14][15][16][17][18][19] thì mô men yêu cầu để hạ cọc ống thép có cánh vít xoắn ở mũi và thành cọc được xác định theo công thức sau đây: R u = K t T…”

Parametric Study of Helical Piles Subjected to Compression and Tension Loading Through Finite Element Analysis: A Case Study

“…Although, in principle, helical piles were used as anchors to withstand lifting loads, in recent decades, their application and use have increased, being widely used as a foundation solution in low compacted terrain, supporting lifting, compression, and lateral loads [2]. Its ease of installation using torque and downward pressure represents a significant advantage since it reduces the impact on neighboring structures, decreases installation times, and has greater capacity than perforated piles due to the helical plates increasing the piles' support area [3,4].The torque requirement for the installation of helical piles depends mainly on the ground conditions and the geometry of the pile [5]. The improvement in equipment to generate torsion allows the use of larger diameter helical piles in response to the increased design requirements, and its use is suitable for any project, from the foundation of light poles and wind turbines to the foundation of residential and commercial buildings [6].…”

“…The torque requirement for the installation of helical piles depends mainly on the ground conditions and the geometry of the pile [5]. The improvement in equipment to generate torsion allows the use of larger diameter helical piles in response to the increased design requirements, and its use is suitable for any project, from the foundation of light poles and wind turbines to the foundation of residential and commercial buildings [6].…”