Screw displacement piles are designed to maximise soil displacement, while minimising the noise and vibration generated from installation. While these benefits have increased the uptake of screw displacement piles in the industry, divergences in design standards means there is no definitive consensus on the axial response of these piles. To address this, a high-quality database of load tests on screw displacement piles is presented in this paper – the largest of its kind in the published literature. Both instrumented and uninstrumented records are used to compare four different cone penetration test-based design methods for screw displacement piles in granular soils. The instrumented data show that existing design methods tend to overestimate the base capacity of screw displacement piles yet underestimate their shaft capacity. A linear best fit to the instrumented data shows improved predictions of the total pile capacity when compared to both instrumented and uninstrumented records. However, variability in predictive performance suggests that installation-related mechanisms may influence the overall capacity of these piles, particularly piles with an oversized displacement body. ... Read more

Screw injection piles are a type of screw displacement pile that use grout injection to displace soil around the pile tip and to reduce the installation resistance on the pile. The process results in lower noise and vibrations compared to a driven pile, whilst creating displacement mechanisms considered beneficial to the pile’s capacity. Yet while these benefits have increased the uptake of screw injection piles in the industry, divergences in design standards means there is no consensus on the axial response of these piles, particularly with regards to their load-displacement response for serviceability limit state design. This paper takes two settlement prediction methods for sandy soils and compares their performance to instrumented load tests on screw injection piles from two different sites. In summary, the results suggest that screw injection piles develop little to no prestressing around the pile base during installation into sand, and a stiffness-based formulation could accurately estimate the pile displacement at both test sites. The formulation presents an effective way of predicting pile displacement, allowing for more benefit to be gained out of proof load tests and providing an efficient means of validating the in-situ pile capacity after installation. ... Read more

Suction piles, also known as suction caissons or suction anchors, have been used extensively in the offshore industry since the 1980s. Existing design methods, such as the DNV-GL method, were primarily developed from installations in dense sands or clays. However, with the continued growth in offshore wind energy, suction piles are being installed more and more in intermediate soils, such as silt, sand and clay mixtures. However, problems can arise when using current design methods for forecasting installation response in these soils. Furthermore, it’s also challenging to classify the soil based on CPT measurements, as well as selecting the appropriate design factors for the suction pile’s shaft and base resistance. To evaluate how design methods perform in intermediate soils, a database has been compiled of installation records across 126 piles at three different sites. This paper focuses on the suction installation phase, comparing the performance of different design methods and soil classification methods in predicting the required suction pressures. The performance of three different design methods have been compared, in addition to a sensitivity analysis on the design factors—indicating the likely range of these factors for intermediate soils. ... Read more

Quay walls are often assessed using numerical models to capture highly nonlinear soil behavior and the complex interactions between foundation elements. The input parameters of these models are usually derived from advanced laboratory tests; however, capturing the spatial variation in these properties across large quay walls can prove inefficient and costly. Moreover, the difficulty in performing full-scale load tests or small-scale physical models complicates the validation of the numerical model. This paper addresses these challenges by
using monitoring data during the construction of a deep-sea quay wall in the Port of Rotterdam. The quay wall, installed primarily in sand, consists of an anchored retaining wall with a concrete relieving platform. During dredging in front of the wall, fiber optic sensors and inclinometers measured large changes in anchor forces and wall deflection. These changes were then compared to the predictions of a finite element model with the hardening soil model with small strain stiffness constitutive model, with the input parameters derived from cone penetration tests (CPT). The results from the CPT-based numerical model were in good agreement with the measured data, demonstrating the feasibility of integrating numerical modelling and field monitoring while supporting the use of the CPT to calibrate advanced soil constitutive models. The validated model provides a reliable basis against which hypothetical adaptation or remediation measures to the wall can be assessed, such as changes in the dredged seabed depth and surcharge loading. ... Read more

The InPAD project investigated the axial capacity of different pile types in sand, including driven precast piles, screw displacement piles and driven cast-in-situ piles. This was done through several full-scale field tests and small-scale physical models, using state-of-the-art instrumentation to analyse the base and shaft response of each pile. This article shows some of the findings from the project and puts forward recommendations for the NEN 9997-1 pile design method. ... Read more

To reduce noise and minimize fatigue damage during pile driving, a new installation method has been developed that differs from conventional pile driving with high-frequency impact blows. This method prolongs the hammer blow, causing a slower pressing force. As a result, it reduces stress waves and imposes a quasi-static loading process on the pile. Consequently, this approach may induce different soil response phenomena compared to conventional pile driving. For instance, friction fatigue is a well-known phenomenon whereby the shaft resistance during installation is affected by cyclic loading and geometrical effects. With this in mind, this paper presents field tests on a pile installed with this new piling method in the port of Rotterdam. Using this field test data, this research will explore the differences in soil response between the prolonged-blow installation technique and conventional driving methods, focusing on friction fatigue. ... Read more

As offshore pile foundations increase in diameter and weight, the risk of uncontrolled and unsafe penetration events (pile run) also increases. Traditional approaches to evaluating this risk rely on static resistance to driving (SRD) formulations, equating the SRD to the effective weight of the pile. However, high penetration speeds during uncontrolled pile penetration can lead to a soil response much different to static conditions, particularly with regards to pore pressure dissipation around the pile. With this in mind, the paper proposes an analytical model for determining when uncontrolled penetration may occur and its extent. The model integrates novel SRD formulations with a penetration rate effect model, both of which are derived from cone penetration test (CPT) measurements. The model's predictions were then benchmarked against industry-standard methods using a database of self-weight penetration events in clays and sands of varying densities and strengths. The predicted self-weight penetrations compared well with field observations across the full range of soil conditions and gave a better performance compared to standard prediction methods. Furthermore, the results emphasise the critical role of soil volumetric behaviour during shearing and future research should clarify the influence of rapid penetration on the pile's shaft and base resistance. ... Read more

This study utilises parallel discrete element method (DEM) simulations of cone penetration tests (CPTs) and pile load tests to investigate the application of direct CPT-based methods for predicting the base capacity of bored piles in layered soils. To reduce boundary effects, a coupled DEM-finite difference method (FDM) model is constructed to simulate pile load tests. The study focuses on the scale effect of pile diameter on the correction factor αb and the effectiveness of existing qc averaging methods in layered soils. Two pile diameters and three soil layering conditions, featuring a single silt layer interbedded within sand at varying depths, are considered in the simulations. Results show that both soil layering and pile displacement influence the scale effect. At small settlements (s) up to 0.3 times the pile diameter (D), the scale effect is insignificant, except when a soft layer is directly above the pile tip. At larger settlements, particularly when s > 0.5D, piles with smaller diameters show more pronounced reductions in base resistance due to a weak layer closely beneath the tip. Among the four methods evaluated, the BD-18 qc averaging method produces more consistent αb values across various soil profiles and pile diameters. Microscopic analysis reveals that soils above the tip contribute less to the pile base resistance at s/D = 0.1 than to the cone tip resistance. Additionally, the strength mobilisation levels of soils in most soil layering conditions appear similar at s/D = 0.1, supporting the proposal of a constant αb value in direct CPT-based methods. ... Read more

The future of performance-based foundation design involves integrating Measurement-while-Drilling (MWD) data to enhance the resilience and construction efficiency of pile foundations. During the installation of Drilled Displacement Piles (DDPs), measurements include penetration speed (vz), rotational speed (vr), downward thrust, torque (T) or hydraulic pressure (Pdrill). With these measurements in mind, data from 32 DDPs across 10 project sites in the US and Europe were collected and analyzed. A generalized formulation for installation effort was developed to compare existing pile databases with the data gathered by the authors. The proposed method uses a decomposed installation effort model that separately accounts for the shaft and toe portions of the pile. A regression analysis of the dataset shows the potential of using installation effort to predict pile capacity and provides fundamental knowledge towards establishing a basic framework for estimating pile load capacities during DDP installation. This application highlights the value of real-time monitoring data in performance-based foundation design. ... Read more

This dissertation presents axial compressive load tests where the pile base and shaft resistances were measured with distributed fibre optic sensors. Two test sites were established: one at Amaliahaven in the port of Rotterdam, and another in Delft. At Amaliahaven, the performance of three different pile types was compared in very dense sand: driven precast, driven cast-in-situ and a screw displacement pile type known as a screw injection pile. The screw injection piles were further investigated in the medium dense sand of Delft, comparing screw injection piles installed with a removable casing to screw injection piles installed with sacrificial casings. With these tests, the influence of installation method on the axial pile capacity was examined, and the results were considered in the context of design methods which use the cone penetration test to predict the axial pile capacity.
The piles at Amaliahaven reached very high base and shaft resistances, up to 30 MPa and 600 kPa respectively. These values are nearly three times greater than limiting resistances in design standards, suggesting that limiting resistances lead to excessive conservatism in dense to very dense silica sands. On the contrary, the screw injection piles at Amaliahaven mobilised much lower base capacities than anticipated. This became the focal point for the tests at Delft, and likewise, the piles at Delft also mobilised much lower base capacities than forecasted.
The influence of different installation methods on the pile base resistance was then examined in a review of other instrumented load tests—a review extending beyond screw injection piles and to screw displacement piles overall. The analysis confirmed that the installation of a screw displacement pile leads to little soil improvement around the pile base. In other words, a screw displacement pile tends to mobilise base resistances comparable to a soil-replacing (bored) pile rather than a soil-displacing (driven) pile.
A larger database of both instrumented and uninstrumented test records was then used to consider the implications of these findings. To do so, the base, shaft, and total capacity of each pile was compared to design methods from Belgium, France, the Netherlands and the USA. These design methods tended to overestimate the pile base contribution yet underestimate the shaft contribution, especially at cone resistances greater than the limiting resistances. A best-fit to the measured base and shaft resistances gave the best agreement on average to the measured total capacity. Nevertheless, there is room for improvement with this new formulation, particularly for the shaft resistance of screw displacement piles with an enlarged displacement body.
From the findings in this dissertation, a series of adjustments have been proposed for the Dutch pile design standard NEN 9997-1. The tests presented in the dissertation are also the first set of pile tests to be incorporated into the Dutch national pile test database, with the findings also being used to refine and optimise quay wall design across the port of Rotterdam. ... Read more

Functional demands on quay walls are steadily rising with increases in both ship size and the frequency of port calls, requiring robust safety and performance assessment frameworks. Most existing studies on quay walls remain constrained by simplified analytical or numerical models, limited consideration of failure modes, insufficient model validation, and the absence of site-specific soil correlation, making it difficult to assess real structures under realistic loading conditions. This study presents a novel Cone Penetration Tests (CPT)-driven, performance-based reliability framework that samples directly from measured CPT distributions to preserve field consistent parameter relationships without requiring site-specific covariance matrices. The framework is demonstrated on a recently constructed, full-scale instrumented quay wall in the Port of Rotterdam. A two-dimensional finite element model with the Hardening Soil Small-strain (HSS) formulation is calibrated against
construction-stage monitoring (wall deformations and anchor forces) and coupled to a probabilistic engine to evaluate multiple ultimate and serviceability limit states through an explicit failure tree.

Results indicate that the structural failure of the wall governs the overall reliability of the quay wall, while wall deformation is the most variable response requiring close monitoring. Sensitivity analyses reveal that deeper dredging and higher surcharge loads markedly reduce reliability with wall structural failure governing and serviceability limit states showing the highest sensitivity to these hypothetical changes. The proposed approach provides a generalisable CPT-based methodology for reliability assessment of geotechnical structures based on site investigation data and monitoring data, supporting more informed, data-driven decision-making in design, and life-cycle management. ... Read more

Since most of the existing port infrastructure needs to be upgraded or replaced in the coming decades, the Port of Rotterdam Authority invests in sustainable and future proof design solutions. Together with their partners, they aim to reduce the port’s CO₂ emissions by 50% in 2030 and intend to achieve a zero carbon footprint by 2050. The effective use of new and existing materials is crucial to reach these goals. However, the actual capacity of port infrastructure is generally not precisely known, given that no failures have been observed in practice and the existing berthing facilities are performing very well. In order to derive insight into the reserve capacity of these structures, unique full-scale field tests have been conducted on flexible dolphins, foundation piles and anchor piles. This paper presents the technical, commercial and environmental results of recent pile load tests performed in the port of Rotterdam. The tests have led to a significant reduction of CO2 emissions associated with manufacturing and installing foundations, as well as reducing installation risks. Furthermore, a higher reliability level was obtained using less materials. This paper shows that in spite of the cost of performing full-scale field tests, the verification of the actual capacity of foundation piles is crucial to improve the carbon footprint of port infrastructure.
... Read more

Three driven precast, four driven cast-in-situ, and four screw injection piles were installed and tested in dense to very dense sand at a site in the Netherlands. Each pile was instrumented with two types of fiber optic sensors and tested under axial compression. Through these tests, a comparison could be made of how different installation methods influence the pile base and shaft response. For example, large residual base stresses were measured in the driven precast piles after installation. Of the three pile types tested, the driven precast piles also reached the highest base stresses, mobilizing their full base resistance at comparatively low displacements. The base response of the driven cast-in-situ piles was also like that of a driven precast pile with residual stresses excluded. In contrast, the screw injection piles mobilized much lower ultimate base resistances and with a much lower stiffness. In terms of shaft resistance, the precast piles showed friction fatigue effects in line with existing models, but this effect was not evident for the driven cast-in-situ or screw injection piles. Finally, shaft and base resistances measured in the dense to very dense sand layers were greater than limiting resistances prescribed in several design standards. By taking this into consideration in design standards, the results would help reduce some of the overconservatism present in design and consequently reduce the financial and environmental cost of pile manufacturing and installation. ... Read more

Recent advancements in fibre optic sensing have increased the range of monitoring techniques available for measuring the axial response of full-scale piles. For instance, distributed fibre optic sensing gives a continuous measurement of normal force with depth in a pile, meaning the shaft resistance of a pile can be accurately quantified in each soil layer. Other fibre optic sensing methods, such as Fibre Bragg Gratings, have been shown to provide accurate and robust high-frequency measurements of pile installation. With these improved measurement techniques, detailed insights can be obtained into not just the geotechnical response of the pile, but also the structural response. Presented in this paper is some first-hand fibre optic data collected from axial load tests on piles founded in dense to very dense sand, ranging from driven piles to screw displacement piles. Using fibre optic sensing, key insights could be gained into both the structural and geotechnical response of these piles at large base and shaft resistances, facilitating changes to CPT-based pile design methods at a site-specific and nationwide level. ... Read more

This report presents the execution and results of axial pile load tests on screw injection piles in the south of Delft in 2022. Two types of screw injection piles were tested: a screw injection pile with the steel casing removed (SI, Fundex pile) and a screw injection pile with the casing remaining in-situ (Sic, Tubexpile).The tests were carried out with the guidance of NPR 7201 (NPR 7201, 2017) and NEN 9997-1 (NEN, 2017), with each pile loaded under compression to a pile base displacement of 20%. During this process, strains were measured along the entire pile length, giving comprehensive insights into the pile base and shaft response.

This document provides a factual summary of the results for dissemination to the NPR 7201 advisory committee, with the primary aim of fully detailing of the test methodology and execution, along with the underlying dataset. Minimal interpretation of these results is presented in this report and has instead been published in the following publications:

• Duffy, K.J., Gavin K.G., Korff, M., de Lange, D.A. (2024) Base resistance of screw displacement piles in sand. Journal of Geotechnical and Geoenvironmental Engineering, 150(8), https://doi-org.tudelft.idm.oclc.org/10.1061/JGGEFK.GTENG

• Kevin Duffy (2025) Axial capacity of piles in sand: A field investigation using distributed fibre optic sensing. [Doctoral dissertation, Delft University of Technology]. (to be published)

The data from the tests is publicly available on the 4TU.ResearchData repository under doi: 10.4121/78720ecb-daf4-4676-b5f4-281e93e4388a (Static load tests on screw injection piles with distributed fibre optic sensors in Delft). ... Read more

Understanding the geological and geotechnical characteristics of the shallow subsurface is crucial for engineering decisions in densely populated regions like the Netherlands. Urban areas are for a large part built on a complex stack of sand, clay, silt, gravel and organics that were deposited over the last hundreds of thousands of years under gradually subsiding tectonic conditions. One of these units, a fluvially deposited sand known as the Kreftenheye Formation, is widespread across the western part of the country and is vital for foundation design and groundwater dynamics. The Kreftenheye Formation is therefore well described by geotechnical and geological tests, yet integrating both types of data has rarely been done on a nationwide scale.

This paper focuses on 76 pairs of Cone Penetration Tests and boreholes that include Kreftenheye, out of a full database of nearly 200 pairs from TNO - Geological Survey of the Netherlands, generally reaching depths up to 40 meters. The study reveals significant spatial variations and depositional patterns within the Kreftenheye Formation, illustrating how overlying or interlayered flood plain or soft channel lag sediments influences the response of the CPT. Furthermore, CPT response and borehole samples have helped with making geological distinctions between the upper, Weichselian part of the Kreftenheye Formation and the lower Saalian part, showing how integrating both datasets can give both geological and geotechnical insights. ... Read more

Amsterdam is renowned for its picturesque canals, lined by tall, narrow buildings on either side. Hundreds of kilometres of quay walls support these canals, all founded on long, slender timber piles. Yet many of these quay walls are falling into disrepair and the remaining lifespan of these quay walls is often unknown. Consequently, an extensive amount of research and pilot projects are ongoing, investigating how these walls can be upgraded without intruding on the urban environment. Press-in piling presents an excellent alternative to conventional piling techniques because of its effectiveness in tight working spaces, generating low noise and vibrations as it does so. However, Amsterdam poses some unique geotechnical challenges. Built on marshland, soft clay and peat deposits are widespread throughout. Underlying these deposits are dense sands, the primary load-bearing layer for piled foundations. Understanding how piles behave in these sands is therefore vital, particularly in the case of piles with low embedment depths or in areas where there are thin weak zones in the vicinity of the pile tip. With the growth of press-in piling in the Netherlands, this paper presents some of the opportunities and challenges facing press-in piling, with a particular focus on how the Cone Penetration Test can be used to improve pile design and installation forecasting. ... Read more

Geotechnical structures are often partially embedded, if not fully embedded, making it challenging to assess the remaining lifetime and reusability of a foundation. In-situ monitoring offers a solution. By attaching different types of sensors to a foundation, the foundation’s response and reliability can be assessed at various stages of a structure’s life cycle. To illustrate this, an example of a “smart quay wall” is taken from the Port of Rotterdam. During the design phase, fully instrumented pile tests showed that the design could be optimised, leading to substantial financial and carbon emission savings. During construction, movements and forces in the quay wall were closely monitored and were used to validate a numerical model, thus providing a reliable tool at later stages during the quay wall’s lifetime when reuse or readaptation of the quay wall is being considered. Lastly, ongoing measurements during the operational phase of the quay wall have shown a large amount of residual capacity, particularly when compared to the pile load tests. ... Read more

Currently, the offshore renewables industry uses a range of foundation systems originally developed for the oil and gas sector. However, innovative foundation measures still need to be developed for offshore renewables because of key differences in scale, loading conditions and the geographical areas in which renewable developments are deployed. Furthermore, the large-scale of offshore wind developments means there is often significant uncertainty regarding the ground conditions between site investigation points. With this in mind, this paper explores the potential use of press-in pile technology for offshore renewable development. Firstly the paper looks at how press-in piling data can be used to inform and ground-truth soil models during pile installation, as well as informing the in-service behaviour of a structure. The paper then describes a number of innovations that may allow for reduced costs and environmental impacts of offshore foundations. ... Read more

Full-scale axial load tests were performed on five screw injection piles founded in medium-dense to dense sand at a site in Delft, the Netherlands. Each pile was instrumented with distributed fiber-optic sensors along its full length, giving detailed insights into the shaft and base response under compression loading. The paper focuses on the pile base response and combines the test results with a newly compiled database of instrumented load tests on screw displacement piles in sand. Given the range of screw displacement piles on the market, the influence of different installation methods and pile geometries on the base resistance can be assessed through the database. In summary, the analysis showed that all screw displacement pile types tended to mobilize base capacities similar to bored or nondisplacement piles. Despite high variability in the database, no significant trend with pile geometry, such as length or diameter, was evident. ... Read more