CHD pile performance: part II – numerical modelling

Proceedings of the Institution of Civil Engineers - Geotechnica

Knappett³

et al. 2016

Self Cite

The continuous helical displacement (CHD) pile is an auger displacement pile developed in the UK. It has performance characteristics of both displacement and non-displacement piles due to the way in which it is installed. Based on field experience, it has been shown that the load-settlement performance of CHD piles installed in sand exceeds the current design predictions based upon conservative effective pile diameter and design parameters associated with auger bored or continuous flight auger in situ piles. In an effort to gain a greater understanding of the performance of CHD piles in sand compared with more conventional piling techniques, a programme of physical model pile testing (reported in this paper) and associated finite-element modelling (reported in a companion paper) was undertaken.The model testing programme established that greater shaft resistance may be developed for the piles than had originally been considered. Based upon the results of the model testing, recommendations for more appropriate approaches to the selection of end bearing and shaft resistance factors are made to predict ultimate load capacity in sand.

Section: 1mentioning

confidence: 53%

Section: Introductionmentioning

confidence: 99%

CHD pile performance: part I – physical modelling

Jeffrey

Proceedings of the Institution of Civil Engineers - Geotechnica

Knappett³

et al. 2016

Self Cite

“…The model vertical boundaries were set to 60 times the pile shaft diameter (D p ) in each direction from the pile centreline in order to be compatible with minimal lateral separation specified in other similar studies (i.e. Bolton et al, 1999;Phillips and Valsangkar, 1987), whereas the base of the model was extended to eight times the screw pile helical plate diameter (D h ) below the pile tip for all the models, as verified by Knappett et al (2016) (Figure 2). The top boundary was free to move in all directions whereas the bottom boundary was fully fixed and the vertical side boundaries were allowed only vertical deformation.…”

Section: 1mentioning

confidence: 99%

“…This model has been used in several previous studies where FEA was validated against 1g and centrifuge physical model testing (e.g. Al-Baghdadi et al, 2016;Aldaikh et al, 2014;Al-Defae et al, 2013;Knappett et al, 2014Knappett et al, , 2015Knappett et al, , 2016.…”

Section: 11mentioning

confidence: 99%

“…Where specific parameters were not available they were generated based upon the case study in situ relative density (either reported or determined from standard/cone penetration testing (SPT/CPT) data) using the correlations in Table 1 (Al-Defae et al, 2013). These correlations have previously been successfully used for simulating the results of field pile load tests of CHD piles, as reported by Knappett et al (2016).…”

Section: Validation Of Numerical Modellingmentioning

confidence: 99%

See 1 more Smart Citation

Effects of vertical loading on lateral screw pile performance

Al-Baghdadi

Proceedings of the Institution of Civil Engineers - Geotechnica

Knappett

et al. 2017

The offshore wind energy sector faces new challenges as it moves into deeper water deployment. To meet these challenges, new and efficient foundation solutions are required. One potential solution is to upscale onshore screw piles but they require verification of performance for new geometries and demanding loading regimes. This paper presents a three-dimensional finite-element analysis investigation of screw pile behaviour when subjected to combined vertical and lateral loading in sand. In the investigation, the screw pile length and helical plate diameter were varied on piles with a fixed core diameter while subjecting the piles to combined axial and lateral loading. The results were compared with results from straight shafted piles with the same core diameter. The results of the analysis revealed that vertical compression loads increased the lateral capacity of the screw piles whereas vertical uplift loads marginally reduced the lateral capacity. The downside of this enhanced lateral capacity is that the screw piles experience higher bending moments. This suggests that, when using screw piles for offshore foundation applications, structures should be designed to maintain axial compressive loads on the piles and induced bending moments need to be adequately assessed when deciding on appropriate structural sections.

Developing Screw Piles for Offshore Renewable Energy Application

Advances in Offshore Geotechnics

Davidson

Cerfontaine

et al. 2020

This paper details the work undertaken at the University of Dundee in the last 5 years to develop understanding of screw piles to allow them to be deployed offshore as an alternative foundation type to driven piles used in jacket structures. This has been prompted by several UK and European funded research initiatives to develop silent foundation techniques to mitigate affects on marine mammals and other animals. Current mitigation systems also have significant associated costs and questionable environmental credentials. Prior to starting this work, it was recognized that development would not progress unless the ability to predict installation requirements did not form an early part of the research investigation. This then led to investigation of methods to reduce installation requirements and development of new design approaches for the required new screw pile geometries. This paper details the progress of these investigations which are still ongoing.