Abstract: Semi-submersible foundation, as one of the most feasible platform supporting the floating offshore wind turbine, is developing at a fast pace with the offshore wind turbines moving to deep waters (water depth range: 50–300 m). This paper presents a rather comprehensive review on the semi-submersible foundation. At first, this paper reviews the design of semi-submersible foundations, which includes both the conceptual design and the projects currently under operation. Afterwards, a number of simulation tools employed in previous researches to investigate the dynamics of semi-submersible foundations are summarized. In detail, wind-wave basin tests and numerical simulations concerning the dynamic responses of the semi-submersible foundation under the excitations of wind-wave loads are included. As for basin test, key techniques for simulating the realistic wind-wave fields and for accurately modeling different part of a floating wind turbine are reviewed. As for numerical studies, the free-vortex wake model is outlined, which was introduced to overcome the defects of the conventional blade element momentum theory used commonly in estimating the wind load on the wind turbine blades. Additionally, a novel technique coupling a three-dimensional flow solver EllipSys3D with FLEX5 is discussed.

Abstract: In selecting the type of foundation best suited for mid-rise buildings in high risk seismic zones, design engineers may consider that a shallow foundation, a pile foundation, or a pile-raft foundation can best carry the static and dynamic loads. However, different types of foundations behave differently during earthquakes, depending on the soil–structure interaction (SSI) where the properties of the in situ soil and type of foundation change the dynamic characteristics (natural frequency and damping) of the soil–foundation–structure system. In order to investigate the different characteristics of SSI and its influence on the seismic response of building frames, a 3D numerical model of a 15-storey full-scale (prototype) structure was simulated with four different types of foundations: (i) A fixed-based structure that excludes the SSI, (ii) a structure supported by a shallow foundation, (iii) a structure supported by a pile-raft foundation in soft soil and (iv) a structure supported by a floating (frictiona...

Abstract: Between 1943 and 1961, the Rockefeller Foundation (RF) conducted a programme in technical agricultural assistance in Mexico designed to increase crop productivity and encourage agricultural self-reliance. While this programme was considered successful by both the RF and US development advocates, its `success' was in fact limited to those crops, farmers, and agricultural students that most closely resembled their American counterparts. The programme failed where the American model of agricultural progress did not fit Mexican conditions. What began as an attempt to export American agricultural practice and ideology, then, was modified to address only those elements of Mexican agriculture that were already partly Americanized.

Abstract: The Harbin–Dalian high-speed railway in northeastern China has a significant portion of track foundation built on seasonally frozen ground. Wide-spread frost heave was observed during the first win...

Abstract: This paper will review some of the challenges faced by designers of foundations for very tall buildings, primarily from a geotechnical viewpoint. Some characteristic features of such buildings will be reviewed and then the options for foundation systems will be discussed. A three-stage process of foundation design and verification will be described, and the importance of proper ground characterization and assessment of geotechnical parameters will be emphasised. The application of the foundation design principles will be illustrated via four projects, each of which has presented a different challenge to the designers:

Abstract: Additive Manufacturing (AM) or three-dimensional (3D) printing is a promising technology that enables the direct fabrication of products with complex shapes without extra tooling and fixturing. However, control of 3D shape deformation in AM built products has been a challenging issue. One viable approach for accuracy control is through compensation of the product design to offset the geometric shape deformation. This work establishes an analytical foundation of optimal compensation of 3D shape deformation for high-precision AM.

Abstract: This paper presents some examples of design problems for offshore foundations, drawn from the jack-up industry and the wind turbine industry. The examples are chosen to illustrate some general points about foundation design, geotechnical engineering and its interaction with other disciplines. The first example is drawn from the assessment of the safety of installation of jack-up units (large mobile offshore drilling rigs). It illustrates how more rational approaches can be achieved through a deeper use of probabilistic methods in both the prediction of performance and the assessment of field observations. The second example also comes from jack-up practice, but has wider application too: it addresses the classical problem of the performance of foundations under combined loading, and how this can be understood in a simple theoretical and practical framework based on plasticity theory. The final example comes from the renewables sector, where the rapidly expanding offshore wind industry poses new foundation...

Abstract: A series of laboratory model tests was performed to investigate the behavior of geosynthetic reinforced stiff clay foundation systems under circular loading. The footing consisted of a rigid circular steel plate with a diameter of 150 mm. Five different series of tests were performed in both homogeneous (clay or sand) and layered configurations. The tests used planar geogrid and three-dimensional geocell reinforcements. Test results indicate that both types of reinforcements substantially improve the performance of the stiff clay foundation bed. A maximum threefold improvement was observed in bearing pressure, depending on the reinforcement type. However, geocell was found to be the most advantageous soil reinforcement technique, giving maximum performance improvement.

Abstract: Rock masses are commonly used as the underlying layer of important structures such as bridges, dams and transportation constructions. The success of a foundation design for such structures mainly depends on the accuracy of estimating the bearing capacity of rock beneath them. Several traditional numerical approaches are proposed for the estimation of the bearing capacity of foundations resting on rock masses to avoid performing elaborate and expensive experimental studies. Despite this fact, there still exists a serious need to develop more robust predictive models. This paper proposes new nonlinear prediction models for the ultimate bearing capacity of shallow foundations resting on non-fractured rock masses using a novel evolutionary computational approach, called linear genetic programming. A comprehensive set of rock socket, centrifuge rock socket, plate load and large-scaled footing load test results is used to develop the models. In order to verify the validity of the models, the sensitivity analysis is conducted and discussed. The results indicate that the proposed models accurately characterize the bearing capacity of shallow foundations. The correlation coefficients between the experimental and predicted bearing capacity values are equal to 0.95 and 0.96 for the best LGP models. Moreover, the derived models reach a notably better prediction performance than the traditional equations.

Abstract: Cement fly ash gravel (CFG) pile composite foundation is an effective and economic foundation treatment approach, which is significant to building foundation, subgrade construction, and so forth. The present paper aims at investigating the settlement behaviors of saturated tailings dam soft ground under CFG pile composite foundation treatment, in which FEM and laboratory model test were utilized. The proposed findings demonstrate that CFG pile treatment is effective in reinforcing saturated tailings dam and loading has little influence on settlement of soil between piles. The variation of soil between piles settlement in FEM has a good agreement with the laboratory model test. Additionally, the cushion deformation modulus has a small effect on the composite foundation settlement, although the cushion thickness will generate certain influence on the settlement distribution of the composite foundation.

Abstract: Results are presented for long-term geodetic observations of the settlement of residential buildings erected on driven cast-in-situ piles that are part of foundation frames on loess soil. Stabilized deformations of building foundation beds are compared to the results of analysis using normative methods and simulation of the stress-strain state of the system using two- and three-dimensional versions of the finite element method and a plasticelastic soil model.

Abstract: Soft subgrades are not strong enough to provide the required degree of compaction for a pavement embankment’s foundation. Therefore, it is required to treat the subgrade soil or construct a working platform on top of the soft subgrade to ensure proper compaction of the subsequent layers. The constriction sizes of the granular materials used for a working platform are comparatively higher to restrict the erosion of overlying embankment materials. This condition would lead to severe material loss in the embankment layer in cases where the embankment is constructed with dispersive soil, which becomes structurally unstable in wet conditions and appears to disperse in water. This paper investigates the contact erosion failure at the foundation of a pavement embankment constructed with dispersive soil as a result of groundwater fluctuation. Experimental studies were conducted on a laboratory model test apparatus designed to simulate the conditions in the pavement embankment’s foundation. The experimenta...

Abstract: This paper analyzes the bearing capacity of shallow foundations resting on rock masses subjected to seismic loads based on limit analysis theory. The non-linear twin shear strength criterion is used to consider the effects of intermediate principal stress on the bearing capacity of shallow foundations. The pseudo-dynamic approach is applied to account for the effects of seismic loads on the bearing capacity of shallow foundations. Both the horizontal and vertical seismic acceleration coefficients and the effects of an amplification factor on the upper bound evaluations of the foundation’s bearing capacity are investigated. The ?-functions are then applied to derive the upper bound solution of the load-bearing capacity. A numerical computation is performed and indicates that the seismic acceleration coefficients, amplification factor and the intermediate principal stress parameter significantly affect the bearing capacity of shallow foundations.

Abstract: Currently, there is no reliable design procedure which considers all aspects of liquefaction effects on shallow foundations. There are many light and heavy structures resting on saturated sand with high liquefaction potential in seismic areas. The aim of this experimental and numerical study is to evaluate the performance of two shallow foundations with different contact pressures in liquefaction. The results of the centrifuge experiment of shallow foundations with surcharges of three-story and nine-story buildings on liquefiable sand are presented in detail. Although entire soil profile is liquefied, no liquefaction is observed under the foundations. There is a clear difference in settlement mechanisms observed beneath the shallow foundation and in the free-field. The heavy foundation fluctuated more strongly compared with the lighter one. The effect of soil permeability and contact pressure on foundation response is investigated during numerical study. Subsequently, the experiment is simulated two dimensionally using a fully coupled nonlinear constitutive model (UBCSAND) implemented in a finite-difference program, FLAC-2D. The results show that settlement of foundations increased with the increase of soil permeability. Trends of excess pore water pressure are captured reasonably by the soil model, but the settlement mechanisms are different. The soil model underestimates total liquefaction-induced settlement of shallow foundation, especially for light foundation.

Abstract: Soil mechanics and foundation engineering , Soil mechanics and foundation engineering , مرکز فناوری اطلاعات و اطلاع رسانی کشاورزی