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.

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Historic quay walls in many Dutch cities are supported by an array of vertical timber piles which run through soft soil deposits and rest on a sand layer, providing end-bearing support. As these structures experience horizontal loads, the foundation piles are loaded in bending. This is the dominant loading case of pile foundations of dams, lock heads, and sometimes bridge abutments as well. To accurately model and evaluate the timber pile foundations, a proper estimate of their bending properties is essential. Therefore the mechanical properties of existing spruce foundation piles, retrieved from a historic quay wall (1905) at Overamstel in Amsterdam, Netherlands, were studied. Six piles were subjected to a four-point bending experiment. The outer fiber stress was kept constant between the point loads, leading to a failure at the weakest cross section. Measurements of the curvature and force distribution were taken along the pile length during loading. In addition, biological decay in the outer layer of the timber piles, also referred to as the soft shell, was identified with microdrillings. Internal strains were measured successfully by gluing fiber-optic wires inside the soft shell of the timber piles. The experiments indicated significant variations in modulus of elasticity and modulus of rupture across the tested population, but indicated a strong correlation. Modulus of elasticity averaged 16.5 GPa with a variation coefficient of 0.30, whereas the modulus of rupture averaged 23.2 N/mm2 with a variation coefficient of 0.26. Bacterial deterioration was found to be independent of both the outer pile diameter and the location along the timber pile. The soft shell had an average thickness of 21 mm, but it did not contribute significantly to the structural strength of the piles. This study could present a template for assessing the remaining service life not only of historic quay walls but also of other timber pile foundations under bending loads.

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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.@en

In this study, 2D and 3D modelling strategies are used to represent the behaviour of historical masonry buildings on strip foundations undergoing settlements. The application focuses on a two-story building, typical of the Dutch architectural heritage. An improved 2D modelling is presented: It includes the effect of the lateral walls to replicate the response of the detailed 3D models. The masonry strip foundation is modelled and supported by a no-tension interface, which represents the soil-foundation interaction. Two settlement configurations, hogging and sagging, are applied to the models, and their intensity is characterized using their angular distortion. The improved 2D model that includes the stiffness and weight of the lateral walls agrees in terms of displacements, stress and damage with the detailed 3D models. Conversely, the simplified 2D façade models without lateral walls exhibit different cracking, and damage from 2 to 7 times lower at an applied angular distortion of 2‰ (1/500). The improved 2D model requires less computational and modelling burden, resulting in analyses from 9 to 40 times faster than the 3D models. The results prove the importance of identifying and including the 3D effects that affect the response of structures subjected to settlements.

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Natural soil deposits may possess a highly anisotropic nature. The fabric anisotropy of soils which is induced during the soil formation process can lead to severe variation in field scale responses. Although the influence of fabric on the response of sands is well known and several advanced constitutive models have been developed to account for it, most of the studies incorporating anisotropy have focused on element test simulations while practical boundary value problem simulations are usually omitted. In this paper, the undrained response and liquefaction resistance of anisotropic sand deposits with different inherent fabric anisotropies are numerically investigated through element test simulations and one-dimensional nonlinear effective stress site response analyses. A novel semi-micromechanical constitutive model accounting for the effect of fabric anisotropy on sand liquefaction has been incorporated into a fully coupled dynamic in-house code employing the u-p formulation. The proposed numerical framework shows that, in both element test simulations and site response analyses, the fabric effects stemming from both the inherent and induced anisotropies can significantly influence the liquefaction resistance of sands.@en

This paper describes axial load tests on three full-scale driven precast piles in the Netherlands. The piles were founded in dense to very dense river-deposited sands, a soil that is widespread across the Dutch North Sea sector. The deposit is characterised by cone penetration test (CPT) tip resistances of up to 90 MPa and offers a detailed insight into pile response in realistic offshore conditions. Each test pile was incrementally loaded to failure under compression, while fibre optic sensors measured the changing deformation of the pile. The analysis and interpretation of the load test data focussed on how the three slender piles behaved at large shaft and base resistances. Notably, the piles mobilised base and shaft resistances greater than currently prescribed limiting resistances in design standards, thereby highlighting some overconservatism present when designing piles in dense sand.@en

In this paper, a state-dependent semi-micromechanical framework for anisotropic sands is proposed. A simple constitutive model based on critical state theory and bounding surface (BS) plasticity is used to describe idealized micro-level soil behaviour, and a slip theory based multilaminate framework employed to create a link between the micro and macro level responses of soil. A contact normal based second order fabric tensor is used to create a mathematical description of the anisotropic nature of sand. The proposed constitutive framework can reproduce various soil responses, stemming from both the inherent anisotropy which highly depends on the sample preparation method and induced anisotropy resulting from the applied stress path. This paper presents concise theoretical aspects of the multilaminate framework and the anisotropic elastoplastic constitutive formulation. Finally, the model's performance in predicting sand response is demonstrated under drained and undrained conditions at different stress states, relative densities and loading conditions by simulating Karlsruhe sand, and is examined through a comparison with two other sophisticated constitutive models for sand, namely the Dafalias and Manzari (2004) version of Sanisand and hypoplasticity with intergranular strain.

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This paper demonstrates the use of non-linear finite element modelling to investigate the response of structures subjected to different shapes of subsidence-related ground settlements. The approach is presented with reference to a two-storey unreinforced masonry façade resting on a shallow foundation. Eight realistic settlement shapes, based on field and literature data, are applied in the model with increasing intensity. The intensity of the subsidence profiles is characterized using their (angular) distortion. The extent of the induced damage on the façade is objectively and directly quantified by a damage parameter, based on the number of cracks, their length and opening. The performance of different settlement indicators and corresponding limiting values, typically employed in the state of the art, is in this paper discussed in relation to the damage modelling strategy; these are observed to be dependent on the shape of the settlement profiles. The aim of this paper is thus to provide insight into the extent to which the vulnerability of masonry buildings depends on the shape of the subsidence pattern and may serve as a warning not to use (deterministic) damage indicators such as angular distortion without considering the settlement shape.@en

In the Netherlands, the potential damage to the building stock due to subsidence phenomena has recently received increased awareness. However, evaluating and predicting damage to buildings in subsiding areas is a complex task that requires associating the vulnerability of exposed structures with the intensity of the subsidence hazard. Considering the widespread presence of subsidence-related damage to the built heritage, the focus of this study is to provide empirical-based insights to assess and forecast subsidence damage to masonry buildings. A rich dataset with manual levelling measurements was collected comprising 386 surveyed masonry buildings, mainly low-rise (terraced) houses built before 1950. Of the total set of buildings, 122 cases rest on shallow foundations and 264 on piled foundations. For each building, the recorded damage is related to the settlement, calculated from the bed-joint levelling measurements, using four different intensity parameters, namely differential settlement, rotation, relative rotation and deflection ratio. These four parameters are appraised in their capacity to effectively predict the intensity of the damage. The Receiver Operating Characteristic (ROC) method is used to evaluate the relative efficacy of the selected hazard parameters. The rotation, the relative rotation (angular distortion) and the deflection ratio are observed as the most accurate when predicting the intensity of damage, while the differential settlement appears less accurate. Additionally, the dataset was used to generate empirical fragility curves where the probability of damage is described as a function of the aforementioned parameters. Thresholds were set to distinguish between the light damage and the functional and structural damage state. At a relative rotation of 1/500 masonry buildings on shallow foundations were observed to reach or exceed light damage with a probability of 13%, and functional and structural damage with 5%. The availability of the bed joint levelling measurements made it possible to classify eight recurrent settlement profiles, including both symmetric and asymmetric profiles, associated with both the overall deformation and the rigid rotations of the surveyed buildings.@en

This paper presents an improved 2D modelling strategy which aims to represent the behavior of historical unreinforced masonry buildings on shallow foundations subjected to ground settlements. The application is presented with reference to a two-storey building, typical of the Dutch built heritage. The novelty comprises the inclusion of the effect of the lateral house-to-house separation walls of such old buildings. Additionally, the masonry strip foundation is modelled and supported by a boundary interface representing the interaction between the soil and the foundation. Two realistic hogging and sagging settlement configurations are applied to the model and their intensity is characterized using the angular distortion of the settlement shape. The response in terms of damage and deformations of the proposed modelling strategy is compared with the ones of five selected approaches based on the state of the art. For all the selected models, the damage severity is quantified objectively by means of a scalar parameter, which is computed considering the cracks’ number, length, and width.

The results of the proposed 2D model agree in terms of displacements, crack patterns and damage with the 3D models. On the contrary, the façade models that do not include the effect of the lateral walls do not exhibit the same cracking and damage, resulting in lower damage and deformations for the same applied angular distortion. Accordingly, the proposed modelling strategy requires less modelling complexity and the analyses are 9 to 28 times faster to run with respect to the 3D models. The efficient and accurate model allows performing a wide number of analyses to easily investigate the role of the various building’s features.@en

Experimental studies show that initial fabric and its evolution under different stress paths greatly influences soil behaviour. Even though different sample preparation methods create different inherent anisotropies and cause different material responses, the same initial fabric structure under different stress paths also results in different material behaviours. In this paper, a simple state-dependent, bounding surface-based elastoplastic constitutive model, which can simulate the anisotropic nature of sands including the effect of principal stress rotation, is described. The model is developed based on a semi-micromechanical concept within the multilaminate framework and, to include the inherent anisotropy of sand, a deviatoric fabric tensor describing the initial microstructure is introduced. In addition, a fabric evolution rule compatible with anisotropic critical state theory is employed to describe the evolving fabric structure and induced anisotropy towards the critical state. In contrast to the classical strain-driven formulation for fabric evolution, a micro-level evolution rule is proposed. This paper presents concise theoretical aspects of the multilaminate framework and the anisotropic elastoplastic constitutive formulation. The model's capability under drained and undrained monotonic loading conditions at different stress states, relative densities and principal stress orientations is demonstrated by simulating experimental data for Toyoura sand.

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This study aims to investigate the damage response of unreinforced masonry (URM) façades resting on strip foundations and subjected to ground settlements via numerical models. The models depict the non-linear constitutive behaviour of both the masonry, via smeared cracking, and of the soil-foundation interaction, via nonlinear interface elements. The influence of building features, such as the masonry material, the length over height (L/H) ratio of the geometry, the wall thickness, the number and size of openings and different types of strip foundations (i.e. reinforced concrete and unreinforced) is examined. A sensitivity study additionally investigates the influence of the interface stiffness and its constitutive model. A Gaussian curve is used to replicate the shape of the ground settlements; These simulate the loss of support underneath the foundation due to urban subsidence. Eight settlement shapes are applied in the FE models, including both symmetric and asymmetric profiles, while the angular distortion is used to measure their intensity. A new aspect is that the extent of the induced damage to the façade is assessed objectively using a damage parameter that represents the number, length and width of cracks in a single scalar value. The method distinguishes between the applied settlement profile at the bottom of the interface and the retrieved settlement profile measured on the façade. The analyses indicate that for a value of the angular distortion equal to 2 ‰ (or 1/500), computed from the resulting deformations of the façades, 60% of the models exhibit serviceability damage associated with cracks of about 5 mm width. Accordingly, the limit values available in the literature are observed to be too optimistic and not conservative in relation to the analyses presented in this study. A key outcome is that facades with an L/H smaller or equal to 1 do not exhibit cracks wider than 1 mm. Façades on reinforced concrete foundations were observed to be less susceptible to settlement damage, compared to unreinforced ones.

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This paper presents an integrated analysis based on the use of multi-source wide-area datasets consisting of hydro-mechanical properties of geomaterials, in-situ investigations/measurements (e.g. groundwater levels in wells) and innovative space-borne data (i.e. DInSAR techniques) to support numerical analyses aimed at assessing and predicting the settlements affecting built-up areas in variable soil conditions. To this aim, an expeditious procedure was developed and tested with reference to a district in Rotterdam City (The Netherlands) affected by subsidence phenomena due to the presence of heterogeneous settling strata mainly composed by peat and organic soils. The results obtained allowed investigating the role of predisposing factors of the settlement occurrence and assessing the induced damage on buildings. Considering the widespread diffusion of such geohazards, the followed procedure could help the in-charge authorities to carry out activities at urban scale aimed at identifying the areas most affected by subsidence risk and to select the most suitable and sustainable mitigation strategies.@en

This study presents a novel framework in which numerical modelling contributes to the performance of district-scale, subsidence-induced damage assessment in cities where ground settlements affect entire quarters. Therein, the implementation of expeditious procedures offers geotechnical engineers the possibility of contributing beyond the typical site scale. For this purpose, several “typified” hydro-geomechanical-loading (HGL) models, which represent (simplified) scenarios of masonry buildings undergoing settlements, were set up to account for different predisposing or triggering factors (i.e., soil heterogeneity, loading conditions, and groundwater variations) of settlement occurrence in built-up areas. These models exploit multi-source, wide-area input datasets encompassing the hydro-mechanical properties of geomaterials, in situ investigations and measurements (e.g., groundwater levels in wells), and innovative remote sensing data (i.e., DInSAR techniques). With reference to a district in Rotterdam City (the Netherlands), which was built on “soft soils”, the numerical simulations of different scenarios (i) provide an overview of the comparative role of predisposing or triggering factors on settlement occurrence and (ii) allow assessments of the expected induced damage to masonry buildings over 30 years with the exploitation of fragility curves. Considering the widespread diffusion of such geohazards, the proposed approach could help prioritise (rather expensive) maintenance work to the built heritage within sustainable strategies for subsidence risk mitigation.

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A quay wall directly next to a building, both dating from around 1870, collapsed along the Grimburgwal in Amsterdam, the Netherlands, on 1 September 2020. The historic quay wall consisted of a masonry wall, built of a timber deck supported by several rows of timber piles of about 12 m long. As over 200 km of such quays exists in Amsterdam and streets are usually very busy, the collapse triggered the question of the safety of the remaining quay walls in the city. A forensic investigation was carried out to determine the failure mechanisms and factors that contributed to the collapse. The investigation aimed to learn from this event and to prevent similar failures in the future. The main failure mechanisms and contributing factors were identified and confirmed using an integrated model of the quay, which is both simple and robust. The model was used to perform a sensitivity study taking all relevant uncertain factors into account. This work provided valuable insight into the main collapse mechanisms of the wall. Based on the results of this forensic study, it is possible to assess other historic quays.

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The historic canal wall structures in many Northern European cities have been built as masonry walls on a timber deck founded on timber piles. For analysis of the resistance of those structures and assessment of their remaining service life, suitable and accurate calculation models are needed. Thereto an analytical method was developed for modelling laterally loaded pile groups in layered sloping soil. In the proposed method, the bending of a pile, which is subjected to a lateral load and axial load, is described by a beam on a Winkler elastic foundation in which the soil behaviour is represented by a series of independent p-y springs, idealized with a bilinear elastic-perfect-plastic approximation. The plastic limit was computed with Brinch Hansen ultimate soil resistance and the elastic soil response by the Ménard stiffness. The plastic limit was corrected for each depth, based on the reduction of the passive soil wedge due to pile group effects and the presence of a sloping surface. The analytical model was calibrated and validated with three field experiments, one full-scale lateral load test of a 3 × 5 pile group in soft clays and silts (Snyder, 2004), one full scale lateral load test of a single pile located on a slope in layered soils (Mirzoyan, 2007) and one small scale lateral load test of a single pile located near a slope in sand (Abdelhalim et al., 2020). The proposed method can adequately predict bending moment distributions and pile deflections and in addition, a good consistency between the analytical model and experimental tests was observed. The method is very fast, making it suitable for probabilistic, Monte Carlo type, simulations and reliability updating to determine the probability of failure of quay walls or other structures with horizontally loaded piles.

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Large areas of the Netherlands are dominated by deep, soft soil deposits, posing a challenge to engineers with respect to the design of axially loaded foundations. The design of these foundations is primarily based on methods which use cone penetration test (CPT) parameters, such as that outlined in the Dutch national standard NEN 9997-1. A recent update to this standard included revised reduction factors for the pile base resistance. However, it is believed that this update is overly conservative in certain design situations, leading to increasing cost, environmental impact and difficulty of installation. As a result, a national research project was initiated to enhance the understanding of pile-soil interaction effects and their influence on pile design methods. As part of this project, a series of large-scale field tests on fully instrumented piles in dense sand has been executed and are being analysed with a view to refining the national standards and contribute to the existing knowledgebase on piles worldwide. This paper shall provide an overview of two pile test sites that have been developed as part of the programme, along with the design of the testing programme and an overview of the results.@en

Stresses generated from pile installation are a critical component in understanding pile behaviour. These are known as residual stresses and in Delft, the Netherlands, the response of three driven precast piles founded in sand was measured using distributed fibre optic sensing as part of a series of full-scale static load tests. The instrumentation set-up and analysis is discussed in this paper, highlighting the uncertainties with developing an appropriate residual stress distribution and in particular, how instrumentation selection, positioning and calibration can influence the interpretation of the residual stress profiles. The resulting profiles shows a substantial development of residual stress in the pile, an important consideration to take into account when preparing and analysing full-scale load tests on driven precast piles. @en

The use of geogrids to anchor Sheet Pile Walls (SPW) is relatively new. A series of small-scale tests was performed to investigate the behaviour of geogrid-Anchored SPWs subjected to strip footing surcharge loading. Particle Image Velocimetry (PIV) techniques were used to measure soil displacement and analyse the global failure mechanism and dominant soil-geogrid interaction mechanisms. One of the tests was duplicated in a test box that was eight times as wide, showing that the influence of the small width of the test box was acceptably small. A 2D finite element model (PLAXIS) was used to simulate the tests and there was a reasonable match with the test results. The position of the strip footing load, and the length and number of the geogrid anchors, proved to be key factors in determining the bearing capacity. The results provide new insights into the stabilising effect and the effective length of the geogrid anchors, in other words the length along which geogrid-soil friction is mobilised. Contrary to the Dutch design guidelines for reinforced soil walls and conventionally anchored sheet pile walls, the results showed that the geogrid provides resistance in the active zone under the strip footing surcharge loading.

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