Showing papers on "Foundation (engineering) published in 2014"
TL;DR: This work was partially funded by the University of Alicante (vigrob-157, uausti11–11, and gre09–40 projects), the Swiss National Science Foundation (FNS-138015 and FNS-144040 projects) and by the Generalitat Valenciana (project GV/2011/044).
225 citations
TL;DR: In this article, a scale-model energy foundation installed in an unsaturated silt layer with endbearing boundary conditions was evaluated using embedded strain gauges and thermocouples.
Abstract: This study presents a centrifuge modeling approach to characterize the transient thermomechanical response of energy foundations during heating-cooling cycles to provide data for calibration and validation of soil-structure interaction models. This study focuses on the response of a scale-model energy foundation installed in an unsaturated silt layer with end-bearing boundary conditions. The foundation response was assessed using embedded strain gauges and thermocouples. Other variables monitored include foundation head displacements, soil surface displacements, and changes in temperature and volumetric water content in the unsaturated silt at different depths and radial locations. Measurements during the initial heating process indicate that the thermal axial stress is greater near the toe of the foundation as a result of the restraint associated with mobilization of side shear resistance along the length of the foundation. The thermal axial strains were close to the free-expansion thermal strain...
165 citations
TL;DR: In this paper, the experimental results of an in situ tension thermo-mechanical test on an energy pile performed in a very stiff high plasticity clay were reported, where the pile was subjected to thermal loading by circulating hot water in fitted pipes, simulating a thermal load in a coolingdominated climate, at different levels of mechanical loading.
Abstract: Energy piles make use of constant and moderate ground temperature for efficient thermal control of buildings. However, this use introduces new engineering challenges because the changes of temperature in the foundation pile and ground induce additional deformations and forces in the foundation element and coupled thermo-hydro-mechanical phenomena in the soil. Several published full-scale tests investigated this aspect of energy piles and showed thermally induced deformation and forces in the foundation element. In parallel, significant progress has been made in the understanding of thermal properties of soils and on the effect of cyclic thermal load on ground and foundation behavior. However, the effect of temperature on the creep rate of energy piles has received practically no attention in the past. This paper reports the experimental results of an in situ tension thermo-mechanical test on an energy pile performed in a very stiff high plasticity clay. During the in situ test, the pile was subjected to thermal loading by circulating hot water in fitted pipes, simulating a thermal load in a cooling-dominated climate, at different levels of mechanical loading. The axial strain and temperature in the pile, and the load–displacement of the pile were monitored during the tension test at different locations along the center of the pile and at the pile head, respectively. The data showed that as the temperature increases, the observed creep rate of the energy pile in this high plasticity clay also increases, which will lead to additional time-dependent displacement of the foundation over the life time of the structure. It was also found that the use of geothermal piles causes practically insignificant thermally induced deformation and loads in the pile itself.
117 citations
TL;DR: In this article, the authors proposed a method to solve the problem of artificial neural networks in the context of artificial intelligence. National Basic Research Program of China [2007CB310500]; National Natural Science Foundation of China[61376073]
116 citations
TL;DR: In this paper, a 2D solution to the 3D problem is proposed to explore the thermal behavior of a multi-pile seasonal storage system subjected to thermo-mechanical loading from both thermal and mechanical perspectives.
105 citations
TL;DR: In this paper, failure envelopes derived from an extensive program of three-dimensional finite-element analyses were used to evaluate the sliding and rotational capacity of a shallow mudmat.
Abstract: Mudmats are used in the offshore oil and gas industry to support subsea infrastructure for pipeline terminations and well manifolds. Expansion and contraction of connected pipelines and jumpers due to changing thermal and pressure conditions impose fully three-dimensional loading on the foundations, dominated by horizontal, moment and torsional loading rather than high vertical loads. The mudmat foundations are rectangular, and include shallow skirts in order to increase capacity, particularly for sliding. Offshore design guidelines for shallow foundations tend to excessive conservatism; optimisation of mudmat capacity under general loading has thus become critical in order to keep foundation footprints within the limits of current installation vessels. The paper presents an alternative design method, based on failure envelopes derived from an extensive programme of three-dimensional finite-element analyses, focusing on the sliding and rotational capacity of the foundation. Starting from expressions that ...
83 citations
TL;DR: In this article, a new configuration of seismic isolation foundation containing several concrete layers and some rubber blocks is proposed, where the concrete layers are placed periodically to form a periodic foundation, and an equivalent analytical model is established.
76 citations
TL;DR: In this article, the capacity of a wide-shallow bucket foundation was determined by the displacement of the bucket and the corresponding load under a vertical displacement of 0.06D. The vertical loading had an amplification effect on the horizontal load-bearing and moment capacity.
68 citations
TL;DR: In this article, the authors investigated the cause of the overturning failure of a 13 storey residential building in Shanghai, China, by plane strain finite element analysis (FEA) and found that the failure was probably initiated by the formation of tensile cracking in the reinforced concrete piles located under the side of the building adjacent to an excavation.
63 citations
TL;DR: In this paper, the authors describe two such structures that were built to full scale and instrumented, and they were constructed using RCDW as backfill material and were built on a foundation soil prone to fabric collapse due to increased stress and/or increase in moisture content.
Abstract: Geosynthetic reinforced soil walls are now an accepted technology for the solution of earth-retaining problems due to cost savings, easy and quick construction, and associated environmental benefits. Additional savings and reduction in environmental impact can be realised by using recycled construction and demolition waste (RCDW) as the backfill material. This paper describes two such structures that were built to full scale and instrumented. One of the walls was reinforced with a woven polyester geogrid (wall 1) and the other (wall 2) with a relatively more extensible nonwoven polypropylene geotextile. Both walls were constructed using RCDW as backfill material and were built on a foundation soil prone to fabric collapse due to increased stress and/or increase in moisture content. During the monitoring period the walls were subjected to a rainy season followed by induced inundation of the foundation to trigger soil fabric collapse. The results showed that foundation soil collapse influenced wal...
59 citations
TL;DR: In this article, a cyclic lateral loading arising from waves and wind, which is not typically uni-directional over the lifetime of the structure, is described. But the authors do not consider the effect of wind and waves on foundation piles.
Abstract: Foundation piles supporting offshore structures experience cyclic lateral loading arising from waves and wind, which are not typically uni-directional over the lifetime of the structure. This paper...
TL;DR: In this paper, a series of static horizontal loading tests were carried out on three types of foundation models, i.e., piled raft, pile group and raft alone models, on sand using a geotechnical centrifuge.
TL;DR: In this article, an extensive parametric study for geosynthetic-reinforced column-supported (GRCS) embankments was performed using the finite-element method based on the coupled-hydraulic modelling, incorporating the full geometry of the embankment and strain-softening behaviour of deep cement mixed (DCM) columns.
Abstract: This paper presents an extensive parametric study for geosynthetic-reinforced column-supported (GRCS) embankments. The analysis was carried out using the finite-element method based on the coupled-hydraulic modelling, incorporating the full geometry of the embankment and strain-softening behaviour of deep cement mixed (DCM) columns. The influencing factors considered in the parametric study were elastic modulus of DCM columns, area replacement ratio (ARR) based on spacing and diameter of DCM columns, elastic modulus and permeability of soft foundation soil, stiffness of the geosynthetic reinforcement, thickness of the platform layer and friction angle of the fill material. Embankment behaviour during the parametric study was investigated by comparing maximum total and differential settlements, maximum tension in the geosynthetic, maximum lateral deformation of columns, efficiency coefficient of columns and arching ratio. The influencing factors were ranked based on their degree of influence on t...
TL;DR: In this paper, a three-dimensional porous model based on Reynolds-Averaged Navier-Stokes equations and Biot's poro-elastic theory is developed by integrating 3D wave and seabed models to simulate the wave-seabed-structure interaction around the high-rising structure foundation used in the Donghai offshore wind farm.
TL;DR: In this article, the authors describe the stability of a breakwater foundation under the action of seepage based on the results of model tests and FEM analyses and reveal the effect of the reduction in bearing capacity.
TL;DR: In this article, reinforced soil beds are used as an efficient method to build artificial foundations based on weak soils, where the dimensions of compacted beds quite often appear to be overestimated, and this results in increase in costs and working hours needed to construct artificial foundations.
Abstract: Changing a layer of weak soil in deformed foundation with a compacted soil bed consisted of various strong materials (sand, gravel, pebble-gravel, production waste materials). Existing calculation methods and techniques to build compacted soil beds based on weak highly compressive soils do not meet up-to-date requirements. Calculation methods used the dimensions of compacted beds quite often appear to be overestimated, and this results in increase in costs and working hours needed to build artificial foundation. The paper presents the possibility of using reinforced soil beds as an efficient method to build artificial foundation based on weak soils.
TL;DR: In this paper, a series of numerical simulations that were carried out on idealized 3·6, 6, and 9 m-high modular block walls seated on foundations having four different compressibility values.
Abstract: Most geosynthetic and metallic reinforced soil walls are designed assuming that the wall foundation is rigid and/or does not influence the magnitude and distribution of reinforcement loads under operational conditions. This assumption may not apply to walls constructed over compliant (compressible) foundations. This paper describes the results of a series of numerical simulations that were carried out on idealized 3·6, 6, and 9 m-high modular block walls seated on foundations having four different compressibility values. The walls were constructed with two reinforcement materials having very different stiffness values but the same tensile strength. The results of simulations show that as foundation stiffness decreases, reinforcement loads increase. However, for the two reinforcement materials in this study, the influence of axial stiffness of the reinforcement had a greater effect on wall performance than the foundation stiffness for walls subjected to operational (working stress) conditions at en...
TL;DR: In this article, the authors investigated the group effect of tripod bucket foundations in clay by three-dimensional finite element analysis and found that the bearing capacity of the tripod bucket foundation differs particularly from that of the single bucket foundation due to the interaction among individual buckets.
TL;DR: In this article, the structural design of a new large-scale prestressed concrete bucket foundation (LSPCBF) for offshore wind turbines that take the seismic response of the foundation into consideration is described.
Abstract: Sandy ocean soil is vulnerable to liquefaction under seismic action. This paper describes the structural design of a new large-scale prestressed concrete bucket foundation (LSPCBF) for offshore wind turbines that take the seismic response of the foundation into consideration. Using an integrated finite element model of the soil, bucket foundation, and upper structure that incorporates infinite elements for the soil boundary, the dynamic responses of the upper structure, the bucket foundation, and the soil surrounding the bucket foundation to three types of seismic wave acceleration time histories were determined using time history analysis. The Shanghai artificial seismic wave was used as an example. This wave causes the most intense seismic response of the seismic waves considered, based on the anti-liquefaction shear stress approach to estimating the area of soil liquefaction. The results showed that 88% of the soil outside the bucket in the range of the bucket depth is liquefied. In contrast, only 9% of the soil inside the bucket is liquefied. As the soil depth increases, the liquefaction range decreases substantially. The simulation results show that the LSPCBF can improve the liquefaction resistance of soil inside and directly below the bucket under seismic loading. Finally, the foundation stabilities under an ultimate load before and after an earthquake were compared. The horizontal displacement of the liquefied foundation increased by 41.1% and the vertical differential settlement increased by 6.2% after the earthquake. A large plastic zone was not formed, which means that an LSPCBF subjected to seismic action is still able to support the ultimate load.
01 Jan 2014
TL;DR: In this article, the Griffith flaws and energy balance theory are introduced, and the concept of stress intensity factor for linear elastic fracture mechanics is introduced, followed by a description of the criteria for fracture propagation.
Abstract: This chapter provides the basic theories and principles behind rock fracture mechanics. It starts with introducing the Griffith flaws and energy balance theory, which is the foundation of the modern fracture mechanics. Then the concept of stress intensity factor for linear elastic fracture mechanics is introduced, followed by a description of the criteria for fracture propagation. Also described in this chapter is the subcritical crack growth which dominates the time-dependent long term stability of a fractured medium.
TL;DR: In this article, the authors have shown that high values of soil density can change operating conditions of artificial foundations significantly, i.e. a so-called plate effect can be observed, due to high hardness values highly compacted soil beds allow distributing foundation loads on the considerable part of the area and reducing its value on the edge of the weak layer.
Abstract: The clay loams of semi-solid consistency was tested under static loads. The test results have proved that high values of soil density can change operating conditions of artificial foundations significantly, i.e. a so-called plate effect can be observed. Due to high hardness values highly compacted soil beds allow distributing foundation loads on the considerable part of the area and reducing its value on the edge of the weak layer.
TL;DR: In this article, the authors investigated the deformation of earthen embankments under various liquefiable foundation conditions under mainshock-aftershock sequential ground motions in a series of dynamic centrifuge tests.
25 Mar 2014
TL;DR: In this paper, an energy foundation constructed as part of a new single-story building at the U.S. Air Force Academy has been evaluated during a 39-hour heating test, and a maximum upward displacement of 1.55 mm was observed at the head of the foundation.
Abstract: This paper documents the thermo-mechanical characterization of an energy foundation constructed as part of a new single-story building at the U.S. Air Force Academy. During a 39 hour heating test, the foundation increased in temperature by 21.7 °C, while the sandstone subsurface only increased in temperature by less than 1 °C at a distance of 1.22 m from the center of the foundation. The distributions in thermal axial stress and displacement in the foundation were calculated from the measured thermal axial strain values, and a maximum compressive thermal axial stress of 5.2 MPa was observed near the middle of the foundation, and a maximum upward displacement of 1.55 mm was observed at the head. The thermal axial stresses and displacements measured were well within acceptable limits for structural elements.
TL;DR: In this paper, a simulation method for the mass concrete temperature cracking propagation process using the Finite Element Method (FEM) is introduced to illustrate the concrete heat conduction problem, an example is simulated with FEM to study concrete surface cracks caused by temperature changes during the entire process of pouring concrete, and the example is discussed to demonstrate how the concrete cracking process results from temperature decreases.
31 Dec 2014
TL;DR: In this article, an integrated multidisciplinary approach to design the tower and foundation simultaneously is presented, where aerodynamics, hydrodynamics, structure and soil mechanics are the modeled disciplines to capture the full dynamic behavior of the foundation and tower under different environmental conditions.
Abstract: In the current offshore wind turbine support structure design method, the tower and foundation, which form the support structure are designed separately by the turbine and foundation designer. This method yields a suboptimal design and it results in a heavy, overdesigned and expensive support structure. This paper presents an integrated multidisciplinary approach to design the tower and foundation simultaneously. Aerodynamics, hydrodynamics, structure and soil mechanics are the modeled disciplines to capture the full dynamic behavior of the foundation and tower under different environmental conditions. The objective function to be minimized is the mass of the support structure. The model includes various design constraints: local and global buckling, modal frequencies, and fatigue damage along different stations of the structure. To show the usefulness of the method, an existing SWT-3.6-107 offshore wind turbine where its tower and foundation are designed separately is used as a case study. The result of the integrated multidisciplinary design optimization shows 12.1% reduction in the mass of the support structure, while satisfying all the design constraints.
TL;DR: In this paper, the effects of the soil-foundation interaction on the soil liquefaction resistance around the skirt and under the foundation were analyzed using the ADINA finite-element program.
Abstract: Occurrence of liquefaction in saturated sandy deposits under structure foundation can cause a wide range of structural damages from minor settlement to general failure because of bearing capacity loss. By comparing traditional foundations for offshore wind turbines, the soil inside and underneath the composite bucket foundation is subjected to the overburden pressure from the foundation self-weight and constrained by a half-closed bucket skirt. The objective of this paper is to clarify the effects of the soil-foundation interaction on the soil liquefaction resistance around the skirt and under the foundation. The dynamic response of the composite bucket foundation during earthquake, including coupled soil mode of porous media, is calculated using the ADINA finite-element program. A typical configuration of composite bucket foundation is used for the analysis, and two earthquake waves (peak ground accelerations of 0.035 g and 0.22 g) are applied as the base acceleration. The results show that the composite bucket foundation exhibited good resistance to seismic action by improving the anti-liquefaction capacity of the soil inside and under the foundation because of the overburden pressure of the self-weight and the constraint effect of the skirt.
TL;DR: In this paper, a random field model that describes spatial variations in the design undrained shear strength is formulated and calibrated to account for uncertainty due to spatial variability in foundation design in deep water Gulf of Mexico.
Patent•
19 Feb 2014
TL;DR: In this article, a peaty soft soil stratum subway station construction technology is described. But the method is simple, convenient to realize, quick in construction speed, capable of being ensured in construction quality easily, and good in construction effect.
Abstract: The invention discloses a peaty soft soil stratum subway station construction technology. A main structure of a constructed subway station comprises base plates, side walls, top plates and middle plates distributed between the top plates and the base plates. Underground consecutive walls are arranged on outer sides of the two side walls. The base plates, the side walls, the middle plates and the top plates are all of a rebar concrete structure formed by pouring waterproof concrete. The subway station construction technology comprises the following steps: (1) underground consecutive wall construction, (2) foundation reinforcement, namely, three-shaft stirring piles are used for reinforcing the foundation of excavated foundation pits, (3) vacuum water falling, namely conducting vacuum well point water falling construction on the foundation pits needing excavating, (4) foundation pit excavation, namely, an open excavation method is used for conducting earthwork excavation on the foundation pits needing excavating with a plurality of excavating layers from top to bottom, (5) subway station main structure construction. The method is simple, convenient to realize, quick in construction speed, capable of being ensured in construction quality easily, and good in construction effect, and enables the subway station construction process of peaty soft soil stratum to be completed simply, quickly and with high quality.
TL;DR: In this article, the potential benefits of reinforcing the active zone behind a model sheet pile wall by using polypropylene fiber and cement kiln dust have been investigated experimentally and numerically.