1,720,971 research outputs found
"p-y" curves for piles in radially inhomogeneous soil
No full text“p-y” curves are used to simplify the pile response of laterally loaded piles at any given depth by describing the applied lateral soil reaction as a function of the lateral displacement. Simple analytical solutions in two-dimensions for system stiffness are available by modelling a segment of the pile surrounded by an annular zone of linear-elastic soil. Current solutions assume homogeneous soil conditions. However, installation of a bored pile in clay would result in a region of softened material immediately surrounding the pile-soil interface, which can be modelled using a function describing the variation of shear modulus with distance from the pile. Such functions are available in the literature using linear and power-law variations. This paper derives an improved solution for the system stiffness considering the effects of pile installation. The previously discussed annular zone of soil is split into multiple rings with each able to define an independent shear modulus. A solution for the overall system stiffness is provided. Three-dimensional and parameter effects are discussed
Theoretical “t-z” Curves for Piles in Radially Inhomogeneous Soil
Full text linkAccurate estimates of pile settlement are key for efficient design of axially loaded piles. Calculations of pile settlement can be simplified using one-dimensional “t-z” curves describing pile settlement at a certain depth as a function of side friction. In the realm of this simplified framework, theoretical “t-z” curves can be derived by substituting an attenuation function describing the variation of shear stress with distance from the pile, into a soil constitutive model relating shear strain to shear stress, then integrating with respect to distance to get the settlement at the pile circumference due to an applied shear stress. A handful of analytical “t-z” curves are available in the literature using the concentric cylinder model to define an attenuation function; these include solutions for linear-elastic, power-law and hyperbolic constitutive models. However, radially homogeneous soil has often been assumed, ignoring the effect of the pile installation resulting in unconservative calculations of pile settlement. This paper considers the installation of the pile, resulting in a radially variable shear modulus distribution in the surrounding soil. A radial inhomogeneity correction factor has been developed for selected constitutive models based on two simplified functions for the soil inhomogeneity, which can be applied to the previously derived “t-z” curves produced assuming radially homogeneous soil. The performance of this simplified method is investigated
A simplified analytical model for developing “t-z” curves for axially loaded piles
No full textPile settlement estimation can be simplified using one-dimensional “t-z” curves to describe the relationship between shear stress and settlement at the pile-soil interface at a specific depth. This simplifies the two-dimensional continuum problem to that of a one-dimensional rod. Some analytical “t-z” curves are available in literature; however, to employ these solutions a suitable soil constitutive model, expressed in a flexibility form γ = γ(τ), must be chosen. This must be carefully calibrated against laboratory test data to accurately represent soil behaviour. This paper explores an alternative approach for piles in clay employing a direct similarity-based relationship between a shear stress-strain curve and a “t-z” curve. A linear-transformation factor is derived which can be applied to a representative soil test directly from the site to produce a “t-z” curve, thus removing the need to calibrate/integrate a suitable soil constitutive model. Suitable values for this factor have been obtained through comparison with existing analytical “t-z” curves
Analytical non-linear "m-θ" curves for monopiles in clay
No full textDependable predictions of monopile foundation response to lateral loads is crucial to the efficient design of offshore wind turbine foundations. For squat monopile foundations, it is important to incorporate the distributed non-linear moment-rotation response with depth, known as “m-θ” curves, in addition to traditional “p-y” curves and lumped force-displacement curves at the pile base. Recognising the limited number of “m-θ” curves available in the literature, this paper develops new theoretical “m-θ” curves using a rational two-dimensional horizontal pile/soil “slice” model to obtain improved representations of the stress and displacement fields in the soil around the pile. Firstly, this model undergoes validation through comparisons with available linear-elastic solutions. Subsequently, it is employed in conjunction with a numerical discretisation of the pile circumference to obtain non-linear “m-θ” curves accounting for both soil yielding and slippage between pile and soil. The resulting curves are compa
Similarity-Based Nonlinear Settlement Predictions of Circular Surface Footings on Clay
No full textThe similarity method, employed to obtain nonlinear settlement predictions in undrained conditions for rigid circular footings on deep clay deposits, was introduced more than 70 years ago. This approach is based on the premise that the pressure–settlement curve of the footing and a stress–strain curve from a characteristic point in the soil can be linearly scaled to collapse into a single master curve. The method has been extended to predict deflections of axially and laterally loaded piles and is widely used in the offshore industry. Despite the theoretical and practical appeal of the method as well as its wide application in a range of geotechnical problems, limited investigation and validation exists in the literature. In this work existing classical similarity methods are reviewed, including a Boussinesq solution for elastic soil and the mobilizable strength design (MSD) method. The similarity factors derived from these methods are compared with those obtained from a novel nonlinear cone model solution, and the resulting expressions are evaluated against rigorous numerical analyses undertaken by the authors in FLAC. These are based on two different nonlinear constitutive models (hyperbolic and tanh) calibrated against triaxial tests from three clay deposits. Two alternative families of similarity methods are also compared with classical similarity, namely, a two-part similarity technique (based on separate scaling factors for elastic and plastic strains) and a stiffness similarity approach (based on secant stiffness degradation). Finally, three field test results are evaluated as case studies to demonstrate the applicability of the method in real-life problems. It is concluded that similarity approaches offer a rational yet approximate tool for nonlinear settlement analysis of footings
Theoretical t-z curves for axially loaded piles
No full textEstimation of nonlinear pile settlement can be simplified using one-dimensional “t-z” curves that conveniently divide the soil into multiple horizontal “slices.” This simplification reduces the continuum analysis to a two-point boundary-value problem of the Winkler type, which can be tackled by standard numerical procedures. Theoretical “t-z” curves can be established using the “shearing-of-concentric-cylinders” theory of Cooke and Randolph-Wroth, which involves two main elements: (1) a constitutive model cast in flexibility form, γ=γ(τ); and (2) an attenuation function of shear stress with radial distance from the pile, τ=τ(r). Soil settlement can then be determined by integrating shear strains over the radial coordinate, which often leads to closed-form solutions. Despite the simplicity and physical appeal of the method, only a few theoretical “t-z” curves are available in the literature. This paper introduces three novel attenuation functions for shear stresses, inspired by continuum solutions, which are employed in conjunction with eight soil constitutive models leading to a set of 32 “t-z” curves. Illustrative examples of pile settlement calculation in two soil types are presented to demonstrate application of the method.<br/
MSD applied to the construction of the British Library basement:a multistage excavation in London Clay
Full text linkThis note presents the application of the mobilisable strength design (MSD) method to the monitoring results of the multi-propped excavation in the south area of the British Library Euston, constructed in a highly overconsolidated stiff clay deposit. The MSD method is an energy-based approach (a nonlinear finite-element method for a single-degree-of-freedom soil-wall system) introduced to develop a simplified design methodology that satisfies both ultimate and serviceability limit states. Wall displacement predictions based on the MSD method are compared with considerable field monitoring data. The sensitivity of the method to reasonable variations in input parameters is considered. A spreadsheet and python code demonstrating the MSD analysis from this paper are provided in the online supplement alongside details of the mathematical formulation
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
- …
