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Stone columns are a popular formof ground improvement that can be applied to a variety of foundation solutions involving soft soil deposits. Many design methods are based on an assumption that columns with a length-to-diameter ratio greater than 4 bulge uniformly along their length. This mode of deformation is not valid for small groups of columns in which interaction between individual columns and the footing gives rise to more complex behavior. The deformational behavior of stone columns at serviceability limit state is of utmost importance, because settlement rather than bearing capacity criteria are generally more onerous in soft soils. The results of some high-quality laboratory studies have been informative in this respect, but the extrapolation of results from small-scale tests comes with the caveats associated with single-gravity laboratory testing. The FEM, in combination with advanced constitutive models, can provide a link between the deformational behavior and settlement performance of discrete column groups at working stress levels. A series of analyses was conducted to examine the influence of key design parameters such as column length, spacing, and the number of columns. The influence of a stiff crust was also examined, because the reference soil profile adopted for these analyses was that of the well-characterized Bothkennar test site. The following three modes of deformation were identified by examining the distribution of stress and strain within columns and the surrounding soil: individual punching, block punching, and bulging. Individual and block punching developed in short or closely spaced columns, whereas block punching was more prevalent in larger groups. Bulging develops in long, widely spaced columns and generally occurs at the point of lowest lateral restraint. In addition, novel parameters referred to as compression and punching ratios were developed to validate the in-depth analysis and identify the principal design parameters that influence the behavior of small groups of stone columns. The results indicate that the mode of deformation is governed by column spacing and length rather than the number of columns. This finding is important, because it indicates that settlement design methods that are developed for large groups of columns are applicable to discrete groups at similar spacings and lengths. It was also observed that the influence of the stiff crust forces bulging to occur deeper and might have led authors in the past to suggest the existence of a critical length. [ABSTRACT FROM AUTHOR]

Monopiles are the most commonly used foundation type for offshore wind turbine (OWT) structures and are characterized by relatively large geometric dimensions, compared with offshore pile foundations typically used in the oil and gas industries. To date, there are no established technical guidelines tailored for the design and analysis of OWT monopiles. This paper first identifies various intrinsic drawbacks involved with the existing design and analysis methodologies as applied to OWT monopiles. Next, a comprehensive experimental program of 1g repeated lateral load tests, performed on a scaled rigid monopile installed in dry sand beds, is presented to investigate its behavior under various loading scenarios. The experimental results provide insights into the various blurry issues in the existing literature related to monopile behavior under long-term repeated lateral loading. Lateral soil resistance profiles were determined from the measured pile bending strain data and found to be markedly dependent on the degree of the polynomial function used for curve-fitting of the bending strain data. Finally, an experimental model is presented for estimation of the pile's accumulated rotation, which takes into account various basic characteristics of the applied lateral load cycles. [ABSTRACT FROM AUTHOR]

Two geotechnical centrifuge tests were designed to elicit the influence of soil-foundation-structure interaction (SFSI) and structure-soil-structure interaction (SSSI) effects on the seismic demands of an inelastic frame structure founded on individual spread footings. Four experimental cases were considered: (1) SFSI of an individual inelastic frame structure (baseline case); (2) in-plane SSSI between the frame structure and a large elastic wall structure designed to respond predominately in a rocking mode; (3) anti-plane SSSI between the frame and wall structures; and (4) combined in-plane and anti-plane SSSI between the frame structure and two wall structures. Results from Cases 1, 2, and 4 are analyzed considering 13 demand parameters. The peak seismic demands from the baseline case are compared to the peak demands from the SSSI cases to elicit the impacts of building adjacency. The number of earthquake motions that resulted in increases or decreases in the seismic demands in the frame structure are tracked for the SSSI cases. For these tests, SSSI consistently results in increased peak foundation moment and foundation base shear demands, regardless of the geometric layout of the structures. These increases propagate throughout the superstructure, resulting in increases in moment, shear and curvature ductility demands in the structural components. SSSI effects are observed to be most significant for low-to-moderate intensity earthquake motions, suggesting that particular consideration should be given to the likelihood of SSSI for highly probable earthquakes. [ABSTRACT FROM AUTHOR]

Conventional bearing capacity analyses for shallow foundations placed on slopes use a modified set of bearing capacity factors based on soil properties, footing geometry, and slope configuration, but are restricted to purely cohesionless or purely cohesive soils. This approach is adequate for establishing bearing capacity on engineered fills with controlled foundation properties, yet does not adequately address design for bearing capacity on soils that have both cohesion and internal frictional resistance--a common scenario for native soils. This role becomes increasingly important in design for mechanically stabilized earth walls, which are often placed on slopes of native c'-φ' soils in which the bearing capacity can often be the critical design constraint. Prior approaches to bearing capacity on horizontal ground for c'-φ' soils utilize principles of limited state plasticity in their formulation, yet the most commonly applied bearing capacity approaches on slopes use semiempirical formulations that employ mutually exclusive soil strength parameters. In this work, results are attained using upper-bound limit state plasticity failure discretization scheme, known as discontinuity layout optimization (DLO), which uses nonassumptive failure geometry (under translational kinematics) in its formulation. The values presented demonstrate important components in consideration of bearing capacity for strip footings placed adjacent to slopes of c'-φ' soils, in particular, the relationship between soil strength properties, slope height to footing width ratio, slope angle, and critical collapse mechanism. A set of reduction coefficients that can be directly applied to the classical bearing capacity formulation is presented for ease of application. [ABSTRACT FROM AUTHOR]

A fully instrumented experiment was conducted to investigate the soil-structure interaction of single short, stiff laterally loaded piles. A hollow steel pipe pile with a diameter of 102 mm, a thickness of 6.4 mm, and a length of 1.524 m was installed in well-graded sand and subjected to increasing lateral load. The pile and surrounding soil were fully instrumented using advanced sensors, including flexible shape acceleration arrays, thin tactile pressure sheets, and in-soil null pressure sensors. The sensors attached to the pile were used to develop the compressive soil-pile interaction pressures and the lateral displacement along the pile length. The tactile pressure sheet sensors provided the soil-pile interaction compressive pressures on the circumference of the pile at a specific depth and along the length of the pile. The measured soil-pile interaction compressive pressures combined with the measured lateral displacement along the pile length were used to develop the soil-pile interaction force-displacement relationships ( curves) using direct measurements. In addition, the in-soil null pressure sensor measurements were used to develop the distribution of horizontal stress changes around the pile as the lateral pile displacement increased. When appropriate, the measured results were compared with data and methods available in the literature. [ABSTRACT FROM AUTHOR]