This paper describes a one-dimensional (1D) computational model for the analysis and design of laterally loaded monopile foundations for offshore wind turbine applications. The model represents the monopile as an embedded beam and specially formulated functions, referred to as soil reaction curves, are employed to represent the various components of soil reaction that are assumed to act on the pile. This design model was an outcome of a recently completed joint industry research project – known as PISA – on the development of new procedures for the design of monopile foundations for offshore wind applications. The overall framework of the model, and an application to a stiff glacial clay till soil, is described in a companion paper by Byrne and co-workers; the current paper describes an alternative formulation that has been developed for soil reaction curves that are applicable to monopiles installed at offshore homogeneous sand sites, for drained loading. The 1D model is calibrated using data from a set of three-dimensional finite-element analyses, conducted over a calibration space comprising pile geometries, loading configurations and soil relative densities that span typical design values. The performance of the model is demonstrated by the analysis of example design cases. The current form of the model is applicable to homogeneous soil and monotonic loading, although extensions to soil layering and cyclic loading are possible.

This paper provides an overview of the PISA design model recently developed for laterally loaded offshore wind turbine monopiles through a major European joint-industry academic research project, the PISA Project. The focus was on large diameter, relatively rigid piles, with low length to diameter (L/D) ratios, embedded in clay soils of different strength characteristics, sand soils of different densities and in layered soils combining clays and sands. The resulting design model introduces new procedures for site specific calibration of soil reaction curves that can be applied within a one-dimensional (1D), Winkler-type, computational model. This paper summarises the results and key conclusions from PISA, including design methods for (a) stiff glacial clay till (Cowden till), (b) brittle stiff plastic clay (London clay), (c) soft clay (Bothkennar clay), (d) sand of varying densities (Dunkirk), and, (e) layered profiles (combining soils from (a) to (d)). The results indicate that the homogeneous soil reaction curves applied appropriately for layered profiles in the 1D PISA design model provide a very good fit to the three-dimensional finite element (3D FE) calculations, particularly for profiles relevant to current European offshore wind farm sites. Only a small number of cases, involving soft clay, very dense sand and L/D = 2 monopiles, would appear to require more detailed and bespoke analysis.

The effect of curing time, content of grout solution and concentration of urea, calcium chloride and urease enzyme on the process of enzymatic calcium carbonate precipitation was analysed. Initially, the process was studied in test-tube experiments by evaluating the amount of calcium carbonate precipitated using X-ray diffraction tests. The method was then applied to stabilise a sandy soil to examine the strengthening effect using unconfined compressive strength tests, X-ray diffraction and scanning electron microscopy. The results showed the effectiveness of the method for improving the mechanical properties of a sandy soil. The soil strength and stiffness increased with increases in content of the grout solution and curing time, while an increase in the concentration of urease and urea–calcium chloride only had a positive effect for lower concentrations. The results also showed a relationship between unconfined compressive strength and calcium carbonate content and pH value.

The PISA design model is a procedure for the analysis of monopile foundations for offshore wind turbine applications. This design model has been previously calibrated for homogeneous soils; this paper extends the modelling approach to the analysis of monopiles installed at sites where the soil profile is layered. The paper describes a computational study on monopiles embedded in layered soil configurations comprising selected combinations of soft and stiff clay and sand at a range of relative densities. The study comprises (a) analyses of monopile behaviour using detailed three-dimensional (3D) finite-element analysis, and (b) calculations employing the PISA design model. Results from the 3D analyses are used to explore the various influences that soil layering has on the performance of the monopile. The fidelity of the PISA design model is assessed by comparisons with data obtained from equivalent 3D finite-element analyses, demonstrating a good agreement in most cases. This comparative study demonstrates that the PISA design model can be applied successfully to layered soil configurations, except in certain cases involving combinations of very soft clay and very dense sand.

9The design of complex underground structures in an urban environment requires in the first instance 10 an appropriate characterisation and interpretation of the ground conditions and of the mechanical 11 behaviour of soil formations in the ground profile. With such information it is then possible to select 12 and calibrate appropriate soil constitutive models for application in advanced numerical analysis, with 13 the objective of predicting the induced ground movements and the potential damage to existing 14 structures and services. This paper provides an interpretation of the site investigation data collected 15 for the numerical analysis and design of the Ivens shaft excavation in Lisbon, Portugal. For the first 16 time a comprehensive set of interpreted data is obtained for two of the main formations in the Lisbon 17 area, Argilas e Calcários dos Prazeres (AP) and Areolas da Estefânia (AE), improving the understanding 18 of their mechanical behaviour and making the data available for application in most soil constitutive 19 frameworks. It is evident from the results that even with careful testing procedures the data may 20 appear to be inconsistent, requiring further assumptions when deriving soil parameters. Such 21 assumptions are discussed and an emphasis is placed on the need to combine data from laboratory 22 and field investigations. 23 24The geology of Lisbon has been influenced by several extreme geological processes (Antunes, 1979; 52 Alves et al., 1980). The oldest superficial soils date from the Cretaceous period, 95 million years ago 53 (Ma), although the majority of the city centre is founded upon Miocene formations, formed around 54 24Ma ago (Moitinho de Almeida, 1991). During this epoch several transgressive-regressive cycles, 55 each corresponding to a depositional sequence, occurred due to tectonic events and due to variations 56 in sea level (Dias & Pais, 2009). This epoch was followed by the last glacial period, when a substantial 57 climate change in the region caused intense erosion and a deflection in the course of the river Tagus 58 (Dias et al., 1997). Only at the beginning of the current Holocene epoch did the water level start to 59 rise again and new sediments began to deposit in the basin. 60The lithological profile at the Ivens shaft site is shown in Figure 2. The top 6 m is a loose sandy fill. 61Underneath are the two main formations, AE down to 35 m, followed by the AP formation. The AP 62 formation was deposited in a marine environment which changed progressively to a sub-tidal zone in 63 shallower waters. The material between 35 and 37 m depth can be considered a different unit (Top 64 AP), as it is lighter in colour (more oxygen) and is more compatible with the latter type of environment. 65

This paper describes the effect of binder and fibre quantity on the mechanical behaviour of a soft soil stabilised with binders and reinforced with steel fibres. Four types of tests were carried out – unconfined compressive strength (UCS), direct tensile strength (DTS), split tensile strength (STS) and flexural strength (FS) tests. The effects of binder quantity (with and without steel fibres) and the effects of fibre quantity were analysed. The results obtained showed that the compressive strength, tensile strength and stiffness increased with binder quantity, but, with the addition of steel fibres, the behaviour changed depending on the strain mechanism of each test. In general, the presence of a low quantity of steel fibres had a detrimental effect in terms of UCS and a negligible impact on the STS, while a beneficial effect was found for DTS and FS. As the fibre quantity was increased, the UCS, STS and FS tests revealed a decrease in brittleness, while the DTS tests showed brittle behaviour with an abrupt and complete loss of tensile strength after failure. The relationships between compressive and tensile strengths are presented in the paper.

The prediction of induced ground movements and the potential damage to existing structures and services is paramount when building deep excavations in an urban environment. In order to obtain a reasonable prediction advanced constitutive models need to be employed, so that the behaviour of the soil can be adequately reproduced under different stress conditions. The calibration of such models is complex and often requires optimisation, as a large number of parameters need to be determined from the available ground investigation data, while also ensuring their consistency with the initial ground conditions. This paper presents the calibration process of advanced constitutive models employed to simulate the excavation of the Ivens shaft in Lisbon, Portugal. The data from both historic and new laboratory and field testing is employed in the calibration procedure. In order to assess and validate the suitability of the derived model parameters, a back-analysis of the nearby Baixa-Chiado metro station excavation is carried out and its results are presented and discussed

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