Showing papers on "Foundation (engineering) published in 2013"

An integral approach to bedrock river profile analysis

Abstract: National Science Foundation (U.S.) (Geomorphology and Land-use Dynamics Program Award EAR-0951672)

Characteristics of a Large-Scale Deep Foundation Pit Excavated by the Central-Island Technique in Shanghai Soft Clay. I: Bottom-Up Construction of the Central Cylindrical Shaft

Abstract: A large amount of field and experimental data has been devoted to rectangular excavations thus far. In contrast, very few data were available for cylindrical excavations, especially those with large diameters in thick soft clay deposits. Via a comprehensive instrumentation program on a 100-m-wide×25.89-m-deep unpropped (self-supported) cylindrical excavation constructed by the bottom-up method in Shanghai soft clay, the characteristics of this large-sized circular excavation were extensively investigated. This cylindrical shaft was a part of a large-scale deep foundation pit excavated by the central-island technique. The investigated items included (1) lateral wall deflections, (2) vertical wall movements, (3) lateral ground movements, (4) ground settlements, (5) subsurface settlements, (6) basal heaves, (7) vertical column movements, (8) column stresses, and (9) variation of pore pressures along depth and artesian water levels. Analysis of the field data indicates that discharging of the deep art...

A framework for understanding energy pile behaviour

Abstract: A descriptive framework for explaining the contribution of the foundation material and various levels of end-restraint, to the response of piles that are loaded thermomechanically, is presented. Th...

Dynamics of offshore wind turbines supported on two foundations

Abstract: Offshore wind turbines are currently considered as a reliable source of renewable energy in the UK. These structures, owing to their slender nature, are dynamically sensitive at low frequencies, the first modal frequency of the system (less than 1 Hz) being very close to that of the excitation frequencies. The majority of operational offshore wind turbines situated in UK waters are founded on monopiles in water depths up to 30 m. For future development rounds where water depths are up to 70 m, alternative foundation arrangements are needed. To date there have been no long-term observations of the performance of these relatively novel structures. Monitoring of a limited number of offshore wind turbines has indicated a departure of the system dynamics from the design requirements. This paper summarises the results from a series of 1:100 scale tests of a V120 Vestas turbine supported on two types of foundation: monopiles and tetrapod suction caissons. The test bed used consisted of kaolin clay and sand. Up t...

Federal Highway Administration Design Manual: Deep Mixing for Embankment and Foundation Support

Abstract: This report provides background on deep mixing for U.S. transportation projects and provides further information on design and construction aspects. This report also includes guidelines required for U.S. transportation engineers to plan, design, construct, and monitor deep mixing projects for embankment and foundation support applications. Considerations for secondary associated applications such as excavation support and liquefaction mitigation are also discussed.

An interdisciplinary approach towards improved understanding of soil deformation during compaction

Abstract: Soil compaction not only reduces available pore volume in which fluids are stored, but it alters the arrangement of soil constituents and pore geometry, thereby adversely impacting fluid transport and a range of soil ecological functions. Quantitative understanding of stress transmission and deformation processes in arable soils remains limited. Yet such knowledge is essential for better predictions of effects of soil management practices such as agricultural field traffic on soil functioning. Concepts and theory used in agricultural soil mechanics (soil compaction and soil tillage) are often adopted from conventional soil mechanics (e.g. foundation engineering). However, in contrast with standard geotechnical applications, undesired stresses applied by agricultural tyres/tracks are highly dynamic and last for very short times. Moreover, arable soils are typically unsaturated and contain important secondary structures (e.g. aggregates), factors important for affecting their soil mechanical behaviour. Mechanical processes in porous media are not only of concern in soil mechanics, but also in other fields including geophysics and granular material science. Despite similarity of basic mechanical processes, theoretical frameworks often differ and reflect disciplinary focus. We review concepts from different but complementary fields concerned with porous media mechanics and highlight opportunities for synergistic advances in understanding deformation and compaction of arable soils. We highlight the important role of technological advances in non-destructive measurement methods at pore (X-ray tomography) and soil profile (seismic) scales that not only offer new insights into soil architecture and enable visualization of soil deformation, but are becoming instrumental in the development and validation of new soil compaction models. The integration of concepts underlying dynamic processes that modify soil pore spaces and bulk properties will improve the understanding of how soil management affect vital soil mechanical, hydraulic and ecological functions supporting plant growth.

On the Foundation of Active Disturbance Rejection Control

Abstract: Prof. Han Jingqing's milestone paper of 1989: ‘Control theory: the doctrine of model or the doctrine of control'showed his deep understanding and complete grasp of the science and engineering of control and it laid the foundation for active disturbance rejection control(ADRC). It is both the origin and the gateway through which ADRC is to be truly understood. To take his critical reflection further, this paper strives to clarify and reflect on the paradigm and foundation of the \"the doctrine of control\", and to continue to explore the essence and significance of ADRC, for the purpose of facilitating further development of ADRC, in theory and in technology.

Pilot-scale load tests of a combined multilayered geocell and rubber-reinforced foundation

Abstract: This paper describes the reinforcing effects of multiple layers of geocell in combination with rubber–soil mixture layers in sand, and compares their behaviour with that of the multilayer...

Insight into the Seismic Liquefaction Performance of Shallow Foundations

Abstract: The mechanisms that control the seismic liquefaction performance of shallow foundations are identified for the special, still com- mon case of a clay crust separating the foundation from the liquefied ground. For that purpose, foundation response is first analyzed with the nonlinear dynamic finite-difference method and consequently evaluated in connection with published field and experimental evidence. Insight is given into the excess pore-pressure buildup under the foundation, the seismic settlement accumulation, the static-bearing capacity degrada- tion, and the inertia-induced interaction with the superstructure. It is thus shown that a naturally or artificially created nonliquefiable soil crust may effectively mitigate the detrimental effects of liquefaction and allow for a performance-based design of surface foundations, without

Motion analysis on integrated transportation technique for offshore wind turbines

Abstract: With the current state of offshore wind turbine construction technology, a major marine spread is necessary for the installation of the foundation, tower, and turbine. It is advantageous for offshore installation to be integrated into a single operation. The large-scale composite bucket foundation is the basis for a one-step integrated transportation and installation technique using a specialized transport vessel. The proposed transportation and installation technique will minimize the offshore operation and maximize the proportion of work carried out onshore with consequent benefits in terms of cost, quality, and safety. The self-floating composite bucket foundation is towed into the semicircle groove of the vessel and connected to the wire ropes of a stationary crane. Then the tower and turbine are attached to the foundation at the shore and the entire unit consisting of the foundation, tower, and turbine is loaded out from the quayside, transported to the site and set down on the seabed. During transport, half of the unit's weight is taken by the hoisting system of the vessel, and the remaining half of the weight is supported by air cushions inside the composite bucket foundation. A detailed model is studied to determine the motions of the vessel with two units to confirm the viability and feasibility of such a method of integrated transportation. The draft and air cushion are two effect parameters used to determine the dynamical characteristics of the transportation structure system. The results show that a smaller draft and a greater air cushion positively contribute to a safe transportation process. The viability and feasibility of this method of integrated transportation are confirmed by determining the motions of the various elements proposed by the detailed model.

Influence of bearing pressure on liquefaction-induced settlement of shallow foundations

Abstract: Earthquake-induced soil liquefaction continues to pose problems for structures on shallow foundations. One particular problem is the excessive settlement that such structures undergo as a consequence of earthquake shaking. For design and insurance purposes it is therefore necessary to be able to estimate the magnitude of these settlements. Current procedures relate the potential settlement to foundation size and liquefiable depth. However, the influence of foundation bearing pressure is also a significant factor. In particular, experimental results have indicated that large bearing pressures may inhibit liquefaction underneath a shallow foundation, resulting in lower induced settlement. By collecting new data from 23 buildings that suffered settlement and tilting as a consequence of soil liquefaction during the 27 February 2010 Maule earthquake in Chile, the existing method of estimating liquefaction-induced settlement is reassessed and shown to require bearing pressure information. Based on both the new ...

Vulnerability assessment of reinforced concrete buildings subjected to seismically triggered slow-moving earth slides

Abstract: The objective of this paper is to develop an efficient analytical method for assessing the vulnerability of low-rise reinforced concrete buildings subjected to seismically induced slow-moving earth slides. Vulnerability is defined in terms of probabilistic fragility curves, which describe the probability of exceeding a certain limit state of the building, on a given slope, versus the Peak Horizontal Ground Acceleration (PHGA) at the assumed “seismic bedrock”, allowing for the quantification of various sources of uncertainty. The proposed method is based on a two-step, uncoupled approach. In the first step, the differential permanent landslide displacements at the building’s foundation level are estimated using a dynamic non-linear finite difference slope model. In the second step, the calculated differential permanent displacements are statically imposed at the foundation level to assess the building’s response to differing permanent seismic ground displacements using a finite element code. Structural limit states are defined in terms of threshold values of strains for the reinforced concrete structural components. The method is applied to typical low-rise reinforced concrete frame buildings on shallow foundations with varying strength and stiffness characteristics (isolated footings and continuous slab foundation), standing near the crest of a relatively slow-moving earth slide. Two different slope models are selected representing a cohesive and a purely frictional soil material. The paper describes the method and the derived fragility curves for the selected building and slope typologies that could be used in quantitative risk assessment studies at site-specific and local scales.

A comparative study of seismic stability of coupled arch dam-foundation-reservoir systems using infinite elements and viscous boundary models

Abstract: In the present paper, a direct time domain procedure is used for dynamic structural stability analysis of the dam-reservoir-foundation coupled system in 3D space considering the impact of the ground motion duration. The foundation medium is assumed to be massed and infinite elements are used for modeling the semi-infinite medium of the foundation. The nonlinear behavior of mass concrete is modeled using the coaxial rotating smeared crack approach with the ability of cracking at Gaussian points. The reservoir is assumed to be compressible and is modeled using fluid finite elements. In order to investigate the effects of the ground motion duration on dynamic stability of the coupled system, a set of artificially-generated ground motions with different duration but the same intensities are used to analyze the system. It is found that the responses of the system with the massed foundation including either infinite elements or viscous boundary on the far-end face of the foundation are the same. Using the massless foundation leads to conservative stresses within dam body. Implementation of the infinite elements leads to decreasing crack profile of the concrete dam compared to the massless model; however higher duration ground motions lead to more damage in both models.

Measured and Predicted Response of a New Jetted and Grouted Precast Pile with Membranes in Cohesionless Soils

Abstract: With increased urbanization, deep foundation (bridges, signage, walls, etc) selection is moving toward the minimization of disturbance and installation time, as well as addressing quality control and assurance issues Unfortunately, many types of deep foundations involve noise and vibration during installation (eg, driven piles) or integrity and reduced resistance issues (eg, drilled shafts, both conventional and post grouted tip, continuous flight auger piles) This paper presents a new foundation type, a jetted and grouted precast pile, which uses the advantages of several proven deep foundation installation techniques The installation of the new pile is comprised of three distinct phases: (1) pressurized water-jetting of a precast pile into the ground; (2) side grouting of the pile; and (3) tip grouting The pile has two separate side grouting zones, each with its own grout delivery system Each grout zone is covered with a semirigid membrane, which results in radial expansion of the soil

Demonstration of Compatible Yielding between Soil-Foundation and Superstructure Components

Abstract: Although the nonlinear behavior of rocking shallow foundations has been experimentally and numerically demonstrated as an effective tool to dissipate vibrational energy during seismic loading, the engineering community has yet to uniformly accept it as a targeted design mechanism for diffusing seismic energy in a structure. This paper presents results of a centrifuge test program that incorporated inelastic behavior into model building systems via yielding of both structural and foundation components. Three 2-story-1-bay building models were designed with similar layouts but different combinations of foundation and structural component yield strengths and were shaken with a similar suite of earthquake motions. Measurements of behavior of each of the model buildings are presented and cross-compared in terms of time history responses, hysteretic responses of the structural and foundation fuses, and maximum response parameters. A balanced design configuration, wherein the rocking foundation and struc...

Introducing Dynamic Nonlinear Soil-Foundation-Structure Interaction Effects in Displacement-Based Seismic Design

Abstract: An iterative linear-equivalent procedure to take into account nonlinear soil-structure interaction effects in the displacement-based seismic design is presented for the case of shallow foundations

Hydrodynamic motion of a large prestressed concrete bucket foundation for offshore wind turbines

Abstract: A large prestressed concrete bucket foundation (LPCBF) was used for the first offshore wind turbine in the Qidong sea area of Jiangsu Province in China. The most critical technique of the foundation is the self-floating towing technique based on a reasonable subdivision inside the bucket. To predict the dynamic behaviors of the LPCBF in waves supported by the air cushion, the hydrodynamic software MOSES is used to simulate the three-dimensional motion of the foundation in the towing construction site. The prototype foundation models are established using MOSES with a water draft of 4 m, 5 m, and 6 m in given environmental conditions. The results show that the hydrodynamic responses of the large floater with air cushions depend not only on the wave conditions but also on the mass of the water column, air cushion height, and air pressure distribution. In addition, the hydrodynamic characteristics can be tuned resulting in small dynamic responses in a particular sea state by changing the draft and water plug height. The floating technique of the LPCBF with supported air cushions in waves is highly competitive for saving cost while using few expensive types of equipment during the towing transportation.