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Alfred Roubos
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1
As open-ended steel pipe piles increase in size, efficient installation methods ensuring sufficient bearing capacity are crucial. A combination of vibratory and impact driving is commonly used to install these piles. However, compression load tests on large-diameter piles installed in this way are scarce, questioning the reliability of design methods for axial bearing capacity. To investigate, four 1·22 m dia. open-ended pipe piles with fibre optic strain sensors were installed and tested at Maasvlakte 2, the Netherlands. All piles were vibratory driven to a depth of 29·5 m; two were then impact driven an additional 3·5 m and two an additional 8·5 m. Static compression load tests were conducted 30 or 70 days post-installation. Although the piles remained largely or fully coring during installation, all experienced ‘locking-up’ of the plug under static loading. The derived resistances were compared with the ‘Unified CPT-based method for driven piles in sand’. This method is intended to capture the capacities of fully impact-driven piles at around 14 days after installation, with further shaft capacity gains likely thereafter. The tests revealed axial resistances that increased over time, matching or exceeding unified method predictions. These findings can impact the design and assessment of open-ended pipe piles.
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As open-ended steel pipe piles increase in size, efficient installation methods ensuring sufficient bearing capacity are crucial. A combination of vibratory and impact driving is commonly used to install these piles. However, compression load tests on large-diameter piles installed in this way are scarce, questioning the reliability of design methods for axial bearing capacity. To investigate, four 1·22 m dia. open-ended pipe piles with fibre optic strain sensors were installed and tested at Maasvlakte 2, the Netherlands. All piles were vibratory driven to a depth of 29·5 m; two were then impact driven an additional 3·5 m and two an additional 8·5 m. Static compression load tests were conducted 30 or 70 days post-installation. Although the piles remained largely or fully coring during installation, all experienced ‘locking-up’ of the plug under static loading. The derived resistances were compared with the ‘Unified CPT-based method for driven piles in sand’. This method is intended to capture the capacities of fully impact-driven piles at around 14 days after installation, with further shaft capacity gains likely thereafter. The tests revealed axial resistances that increased over time, matching or exceeding unified method predictions. These findings can impact the design and assessment of open-ended pipe piles.
Thermomechanical Behavior of an Anchored Quay Wall
Field Observations and Finite Element Analysis
Recent field measurements have revealed that the behavior of quay walls is influenced by air and seawater temperature variations. However, the underlying mechanisms remain insufficiently understood, and current geotechnical quay wall design practices typically neglect thermal effects. This study presents a thermomechanical finite element analysis of an anchored quay wall equipped with a relieving platform at the Port of Rotterdam, supported by several years of field monitoring. The structure consists of a steel combined wall and a reinforced concrete L-shaped front wall. Continuous measurements of wall displacements, anchor forces, and temperatures were compared with the outcome of a numerical finite element model. The study shows that the numerical model was able to reproduce seasonal variations in anchor force and lateral wall displacements induced by temperature changes, aligning well with field observations. Sensitivity analyses revealed that thermal effects amplify with increasing soil-retaining height because of the large exposure to seawater temperature fluctuations. Moreover, the thermal expansion coefficient of soil has a substantially stronger influence on anchor force variations than thermal conductivity. Climate change-related temperature increases further intensify these responses, indicating notable long-Term implications for quay wall performance. The findings provide insight into the observed thermomechanical behavior of the investigated quay wall and show that thermal loading can contribute to the wall response.
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Recent field measurements have revealed that the behavior of quay walls is influenced by air and seawater temperature variations. However, the underlying mechanisms remain insufficiently understood, and current geotechnical quay wall design practices typically neglect thermal effects. This study presents a thermomechanical finite element analysis of an anchored quay wall equipped with a relieving platform at the Port of Rotterdam, supported by several years of field monitoring. The structure consists of a steel combined wall and a reinforced concrete L-shaped front wall. Continuous measurements of wall displacements, anchor forces, and temperatures were compared with the outcome of a numerical finite element model. The study shows that the numerical model was able to reproduce seasonal variations in anchor force and lateral wall displacements induced by temperature changes, aligning well with field observations. Sensitivity analyses revealed that thermal effects amplify with increasing soil-retaining height because of the large exposure to seawater temperature fluctuations. Moreover, the thermal expansion coefficient of soil has a substantially stronger influence on anchor force variations than thermal conductivity. Climate change-related temperature increases further intensify these responses, indicating notable long-Term implications for quay wall performance. The findings provide insight into the observed thermomechanical behavior of the investigated quay wall and show that thermal loading can contribute to the wall response.
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.
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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.