Showing papers on "Foundation (engineering) published in 2004"

Load and resistance factor design (lrfd) for deep foundations

Abstract: This report contains the findings of a study to develop resistance factors for driven pile and drilled shaft foundations These factors are recommended for inclusion in Section 10 of the AASHTO Load and Resistance Factor Design (LRFD) Bridge Design Specifications to reflect current best practice in geotechnical design and construction The report also provides a detailed procedure for calibrating deep foundation resistance The material in this report will be of immediate interest to bridge engineers and geotechnical engineers involved in the design of pile and drilled shaft foundations

Experimental Investigations of the Response of Suction Caissons to Transient Combined Loading

Abstract: Combined loading of foundations is a fundamental problem in civil engineering, particularly in the offshore industry where harsh environmental conditions occur. Large moment and horizontal loads may be applied to the foundation as well as vertical loads. Also, as the waves pass a structure, there can be rapid changes in the loads, so that transient effects need to be considered. When designing shallow foundations, such as suction caissons, there is uncertainty in the current understanding of how the foundation responds to these loads. This paper presents experiments, performed on model suction caisson foundations, where typical cyclic loading conditions are applied. The footing is embedded in oil-saturated sand so that dimensionless drainage times are comparable with the typical offshore conditions. Most of the testing was carried out with the vertical load held constant, to mimic the structural dead weight, while realistic ''pseudorandom'' moment and horizontal cyclic loads were applied. Experiments were carried out at different vertical loads, showing that the response depends on the vertical load level. Nondimensional relationships were established which accounted for this dependency. Surprisingly, the rate of loading had little impact on the load-displacement behavior for the experiments undertaken.

A comparison of the combined load behaviour of spudcan and caisson foundations on soft normally consolidated clay

Abstract: Experimental data from loading tests of model circular footings on soft normally consolidated clay are presented. The experiments were carried out on a drum centrifuge at a radial acceleration level equivalent to 100 times Earth's gravity, ensuring conditions of stress similitude between the model and the prototype scale. The aim of the experiments was to compare the undrained response of different offshore foundations to the same loading conditions. Two different types of foundation were targeted for investigation: spudcans and suction caissons. The spudcan, typically an inverted shallow cone, is the traditional footing for mobile drilling units (also known as jack-up rigs). An alternative foundation concept that is being increasingly considered is that of foundations skirted about the perimeter and installed by suction. A loading arm that incorporated an internal hinge was used so that combinations of load appropriate to the foundations of jack-up units could be applied to the models. Although it was anticipated that, by using skirted foundations there would be increased moment capacity, this was not found to be the case (for the caisson skirt length and soil strength profile investigated). However, there was a stiffer response and additional horizontal capacity at the foundation level. Significantly the use of skirted foundations allowed for a greater combined loading capacity under tensile vertical loads. The results have been interpreted within the framework of strain-hardening plasticity theory, and comparisons with existing yield surfaces are detailed.

Engineering Geology and Construction

Abstract: 1. Land Evaluation and Site Investigation 2. Open Excavation and Slopes 3. Subsurface Excavations 4. Foundation Conditions and Buildings 5. Routeways 6. Reservoirs and Dam Sites 7. Hydrogeology 8. River and Coastal Engineering 9. Waste and its Disposal 10. Derelict and Contaminated Land 11. Geological Material Used in Construction.

Granular Pile Anchor Foundation (GPAF) System for Improving the Engineering Behavior of Expansive Clay Beds

Abstract: Several innovative foundation techniques have been suggested for reducing the detrimental heave of foundations in expansive clays This paper presents another innovative technique in the form of a granular pile anchor-foundation (GPAF) system for arresting heave and for improving the overall engineering behavior of expansive clay beds In the GPAF system, the foundation is anchored at the bottom of the granular pile to an anchor plate through an anchor rod As a result, heave of the foundation is reduced The laboratory model tests using this new concept of the GPAF system revealed that the heave of the expansive clay beds was reduced by about 96 % The development of final heave was faster in the case of the expansive clay beds reinforced with the GPAF system The undrained strength of the clay surrounding the granular pile anchor improved by about 20 % The tests on two-group granular pile anchors indicated that heave was reduced to a minimum value when the spacing between the granular pile anchors was kept at twice the pile diameter The compressive load response of the expansive clay bed reinforced with granular pile anchors also improved The pull-out load of the granular pile anchors increased with increasing diameter and the relative density of the pile

Wind turbine, a method for assembling and handling the wind turbine and uses hereof

Abstract: A wind turbine comprising a foundation (18) and a tower (2) positioned on said foundation (18) is presented. The tower (2) includes more than one modules, wherein the modules each comprises a separate strengthening structure (28) defining the outer edges of the module and wind turbine equipment, and wherein the more than one module are positioned substantially vertically on top of each other in an upright position within the tower (2). The modules are connected directly and/or indirectly through the strengthening structure (28), to the foundation (18). A method for assembling a wind turbine (1) at a wind turbine site and a method for handling more than one wind turbine modules as well as uses hereof are also disclosed.

Foundation for a wind energy plant

Abstract: The aim of the invention is to prefabricate elements which are important for the structural engineering of the foundation of a wind energy plant, i.e. the supporting and lateral stabilising elements of the foundation.

Unified Design of Piled Foundations with Emphasis on Settlement Analysis

Abstract: Design of a piled foundation rarely includes a settlement analysis and is usually limited to determining that the factor of safety on pile capacity is equal to an at least value. This approach is uneconomical and, sometimes, unsafe. Every design of a piled foundation should establish the resistance distribution along the pile, determine the location of the force equilibrium (the neutral plane), estimate the magnitude of dragload from accumulated negative skin friction at the neutral plane, evaluate the length of the zone where the shear forces change from negative to positive direction, establish the load-movement relation for the pile toe and the load distribution in the pile at the time that settlement becomes an issue for the design, and, finally, perform a settlement analysis. The settlement analysis of a piled foundation must distinguish between settlement due to movements caused by external load on the piles and settlement due to causes other than the load on the piles. A fundamental realization of the design approach is that pile toe capacity is a misconception. Each of the mentioned points is addressed in the paper, and a design approach for the design of piled foundations and piled rafts is presented. Examples and case histories are included showing the distribution of measured and calculated resistance distribution along the piles and settlement of soil and piles.

Nonlinear Soil-Structure Interaction: Foundation Uplifting and Soil Yielding

Abstract: The study investigates the response of shallow foundations subjected to strong earthquake shaking. Nonlinear soil-foundation effects associated with large deformations due to base uplifting and soil failure are examined in comparison with the conventional linear approach. Soil behavior is represented with the elastoplastic Mohr-Coulomb model. The interplay between foundation uplifting and soil failure of the bearing capacity type is elucidated under static and dynamic conditions. Research on seismic soil−foundation interaction in the last three decades has mostly relied on the assumption of linear (or at most equivalent-linear) viscoelastic soil behavior and fully−bonded contact between foundation and soil. Seismic design of structure foundation systems has followed a somewhat parallel path : the still prevailing "capacity design" philosophy allows substantial plastic deformation in the superstructure but requires that no significant "plastification" should take place below the ground level. This means that : • foundation elements must remain structurally elastic (or nearly elastic) • bearing−capacity soil failure mechanisms must not be mobilized • sliding at the soil−foundation interface must not take place, while the amount of uplifting must be restricted to about ½ of the total contact area. However, seismic accelerograms recorded in the last twenty years, especially during the Northridge 1994 and Kobe 1995 earthquakes, have shown that very substantial ground and spectral acceleration levels can be experienced in the near−fault zones. Seismic loads transmitted onto shallow foundations in such cases will most probably induce significant nonlinear inelastic action in the soil and soil−foundation interface. Figure 1 illustrates the three possible types of foundation−soil nonlinearity. Observations in past earthquakes confirm the above argument. The most dramatic examples of bearing−capacity and uplifting failures of building foundations took place in the city of Adapazari, during the Kocaeli 1999 earthquake. But such phenomena are not limited to buildings : as an example of a modern monumental bridge, we mention the Rion−Antirrion cable−stayed bridge, the surface foundations of which, despite their colossal 90 m diameter, had to be designed allowing for sliding, uplifting and partial mobilization of soil rupture mechanisms to resist the prescribed high levels of seismic excitation (Pecker & Teyssandier 1998, Gazetas 2001).

Bearing capacity of strip foundations with structural skirts

Abstract: A modified bearing capacity equation is proposed for skirted strip foundations on dense sand. A series of tests on foundation models were carried out to study the factors that affect the bearing capacity of foundations with skirts. Several factors including foundation base friction, skirt depth, skirt side roughness, skirt stiffness and soil compressibility were studied and incorporated in the equation. The results obtained from the proposed equation were compared with the results obtained from Terzaghi, Meyerhof, Hansen and Vesic bearing capacity equations for foundations without skirt. Comparison shows that the use of structural skirts can improve the bearing capacity by a factor of 1.5 to 3.9 depending on the geometrical and structural properties of the skirts and foundation, soil characteristics and interface conditions of the soil-skirt-foundation system.

Bearing capacity of unsaturated expansive soils

Abstract: It is difficult to determine the bearing capacity of a foundation in unsaturated expansive soil, although this is most important. The bearing capacity of unsaturated expansive soil is related to the drying and wetting environment. Swelling pressure occurs when the soil volume change is constrained as an expansive soil is inundated. The expansive lateral pressure, induced by the swelling pressure is similar to the passive earth pressure. By considering the effect of the expansive lateral pressure in Terzaghi's bearing capacity formula, the bearing capacity of unsaturated expansive soil is derived. Because it is very difficult to measure suction in situ, the bearing capacity is expressed using the expansive lateral pressure offers a feasible approach to calculate the bearing capacity of a foundation in unsaturated expansive soil, when suction is not measured. Plate load tests to measure the bearing capacity in situ were performed for the foundation in natural soil and saturated soil immersed by water. The verification of the bearing capacity formulae presented in this paper is conducted by comparing the predicted results with the results of the plate load tests on unsaturated expansive soils in Handan and Bingxia, China.

Embankment dam on liquefiable foundation - dynamic behavior and densification remediation

Abstract: Earthquake-induced liquefaction is a major concern for embankment dam safety. Many liquefaction-induced earth embankment failures or near failures have been reported around the world during various earthquakes. Such embankment damages were particularly destructive when the underlying saturated granular soils liquefied, resulting in cracking, settlement, lateral spreading, and slumping of the embankment. Through a series of four highly instrumented geotechnical centrifuge model tests, seismic behavior of a zoned embankment dam with saturated sandy soil foundation was studied under moderate earthquake conditions. The beneficial effects of foundation densification were investigated. Valuable insights into the dynamic behavior of the employed embankment–foundation systems are provided. Test results suggest that there may be an optimum depth of densification treatment beneath an earth dam beyond which the reduction of the earthquake-induced deformations are relatively minor and that relatively small and isolated zones (e.g., at depth) of loose material within a densified volume of soil may not impair the overall effectiveness of treatment and do not necessarily result in damaging displacements.

Shear transfer plate

Abstract: A wall either wholly or partially made from a shear-resisting assembly that has a shear transfer device, or plate, disposed between the bottom strut and the underlying foundation. The shear transfer device joins the two anchor bolts, eliminating intermediate foundation bolts by transferring lateral shear loads to the anchor bolts in combination with the bottom strut.

Engineering geological problems associated with karst terrains: their investigation, monitoring, and mitigation and design of engineering structures on karst terrains

Abstract: The design and construction of civil engineering structures in karst regions confronts many problems due to unpredictable location, dimensions and geometry of the karst structure and voids. Karst terrain is one of the most intricate grounds to be assessed for civil engineering purposes. Conventional methods of site exploration like desk studies, site reconnaissance, borings, test pits, geophysical techniques, have their advantages and disadvantages; none of them are 100% accurate; therefore they should be used in concert, adapted to each project, the available budget and the undertaken risk. As not two sides are identical in karst, site investigation should be tailored to each site. Factors that should be considered when designing site investigation in karst are: maturity of karst landforms, depth of the karst features, overburden thickness, lateral extent of the karst features, hydrogeology of the area, laoding, etc. The main problems confronted by engineers designing structures on or in karst terrain are: difficulties in excavation and grading the ground over pinnacled rockheads; collapse of the roof over subsurface voids, subsidence of cover soil over sinkhole, difficulties in founding a structure over an irregular or pinnacled rockhead, loss of water from dam reservoirs, pollution of groundwater, etc. A number of solutions have been practiced by engineers to solve these problems like: relocating the structure on a safer site, filling the voids and the fractures with concrete, improving the foundation ground with grouting and/or geogrids, replacing foundation soil, bridging the voids with rigid mats or beams, using deep foundations (piling, drilled shafts, etc.), minimizing future sinkhole development by controlling surface and ground water, etc.

Foundation footing form and accessories

Abstract: Moisture resistant foundation footing form sections constructed from corrugated plastic are disclosed. Supports for holding sections of reinforcing bar, and connecting the side walls of the form sections are included. Also disclosed are tabs and notches in the side walls for use with stakes to connect adjacent form sections. Form sections are disclosed for constructing a corner in a foundation footing form. Step-down forms are disclosed for constructing a foundation footing form on a construction site having surfaces of different elevations. The form sections can be secured in position with stakes, and leveling devices for leveling the form once it is secured in position are disclosed. The form sections disclosed herein can be reused, but they do not attract insects and therefore they do not have to be removed from finished foundation footings.

CMC Foundation System for Embankment Support -- A Case History

Abstract: A wide range of deep foundation systems has recently been developed for construction of embankments on soft soils. Controlled Modulus Columns (CMC) is one technique of ground modification, originally developed in France, for support of light structures such as highway and railway embankments. This paper presents the case history of a column supported embankment project in which 2193 CMC columns were installed up to a depth of 12.5 m to minimize settlement of an embankment. Main challenges were soft ground condition of the site, and the need for an accelerated construction technology for timely delivery of the project. Evaluation of various alternatives, design considerations, construction related issues and monitoring system are discussed in detail.

Development of a Multidisciplinary Engineering Foundation Spiral

Abstract: To operate effectively in today’s workforce engineers need to have a muti-disciplinary perspective along with substantial disciplinary depth. This broad perspective cannot be achieved by merely taking 2 or 3 engineering courses outside of the major, but rather will require a radical change in the way we educate engineers. The faculty of the School of Engineering and Applied Science at the University of New Haven have developed a new approach: the Multidisciplinary Engineering Foundation Spiral. This curricular model provides the needed mix of breadth and depth, along with the desired professional skills, by providing carefully crafted, well-coordinated curricular experiences in the first two years. The Multidisciplinary Engineering Foundation Spiral is a four semester sequence of engineering courses, matched closely with the development of students’ mathematical sophistication and analytical capabilities and integrated with coursework in the sciences. Students develop a conceptual understanding of engineering basics in a series of courses which stress practical applications of these principles. Topics in these courses include electrical circuits, fluid mechanics, heat transfer, material balances, properties of materials, structural mechanics and thermodynamics. Unlike the traditional approach, however, each of the foundation courses includes a mix of these topics, presented in a variety of disciplinary contexts. A solid background is developed by touching key concepts at several points along the spiral in different courses, adding depth and sophistication at each pass. Each foundation course also stresses the development of several essential skills, such as problem-solving, oral and written communication, the design process, teamwork, project management, computer analysis methods, laboratory investigation, data analysis and model development. Students go on to build substantial depth in some of the foundation areas, while other topics may not be further developed, depending on their chosen discipline. Thus the foundation courses serve both as the basis for depth in disciplinary study and as part of the broad multidisciplinary background. This paper will discuss the design and pedagogical philosophy of the Multidisciplinary Engineering Foundation Spiral and describe several of the novel courses in the program.

GeoSupport 2004 : Drilled Shafts, Micropiling, Deep Mixing, Remedial Methods, and Specialty Foundation Systems

Abstract: Proceedings of the GeoSupport Conference: Innovation and Cooperation in the Geo-Industry, held in Orlando, Florida, January 29-31, 2003. Sponsored by International Association of Foundation Drilling (ADSC); Geo-Institute of ASCE. This Geotechnical Special Publication contains 84 papers that analyze foundation systems used in a variety of civil engineering projects in different geologic settings with both soil and rock. Papers provide improved methods of construction and innovative solutions to save costs and time in construction. Case studies of real projects, methods of analyzing difficult earthworks and underground construction, and valuable guidelines are provided. Topics include: geosupport systems; drilled foundations; micropiles; grouting; deep mixing; anchors; and soil nailing.

Load Bearing Mechanism of Piled Raft Foundation during Earthquake

Abstract: This paper deals with the dynamic characteristics of a structure supported by a piled raft foundation. A centrifuge model test and its simulation analysis are discussed first, followed by a parameter survey based on the finite element analysis. In the centrifuge models test, structures supported by a piled raft foundation and by a piled foundation were considered. A parameter survey was performed from the viewpoint of foundation types and types of connection conditions between the raft and the piles. It was found from this study that, although the effect of the pile head connection condition on the response characteristics of a superstructure is fairy small when compared to the type of the foundation, it does affect the load bearing characteristics of piles even when piles are not connected to the raft foundation.

Case Studies of Pile Foundations Undergoing Lateral Spreading in Liquefied Deposits

Abstract: A well-documented case study from the 1995 Kobe earthquake highlighting the performance of pile foundations in liquefied deposits undergoing lateral spreading is presented. The subject of this study is an oil-storage tank supported on 69 precast concrete piles, 23 m long and 45 cm in diameter. The tank is located in the west part of Mikagehama Island, about 20 m inland from the revetment line. During the Kobe earthquake, the fill deposit surrounding the foundation of the tank developed liquefaction. The quay wall moved seawards and consequent lateral spreading of the backfill soils affected seriously the piles supporting the tank. This paper presents results of detailed ground surveying depicting the ground distortion in the backfill soils and observations from field inspection of damage to the piles including bore-hole camera recordings and inclinometer measurements along the length of the pile. The piles were found to have suffered largest damage at depths corresponding to the interface between the liquefied fill deposit and the underlying non-liquefied soil layer. A simplified numerical analysis methodology was developed and used to perform the back-analysis for the piles damaged by the lateral spreading. The location and extent of the damage to the piles computed in the numerical analysis were shown to be in good correspondence with the actual damage observed in the field inspection of two piles of the tank foundation.

Foundation for offshore wind turbines

Abstract: 2.1 The solution of the invention has the advantage that less material is used and produced lower costs for production, warehousing, transportation and erection of the advantage over the prior art. 2.2 The execution of the foundations is such that a central tube is introduced into the lake bottom and at the location is positioned a support structure via the central pipe and lowered. The support legs are anchored into the lake bottom with piles, and the upper ring is positively connected to the central tube. Through this supporting structure the central tube to stress is of sufficient strength that the safe operation of offshore wind power plant is possible. 2.3 The foundation is suitable for the installation of offshore wind turbines.

Diagonal post supporting ground hole for construction

Abstract: The utility model relates to a support used to support the construction foundation pit. The support comprises a sloped beam and a bearing platform. The bearing platform is a reinforced concrete structure and is arranged in the soil of the foundation pit which is arranged below a bottom board of a proposed basement, and a wood pile is pressed below the bearing platform. The sloped beam is a cast-in-place reinforced concrete structure, the lower end is connected with the bearing platform into a whole body, and the upper end is connected with an earth-retaining object or a crown beam which is arranged at the top of the earth-retaining object. Compared with the prior art, the utility model has the advantages that: 1. the sloped beam uses the reinforced concrete structure, the support force is big, the consumption of the earth-retaining object can be reduced, and the cost is lowered; 2. the foundation pit excavation is easy, the sloped support does not need to be arranged layer-by-layer, the large area one-time excavation can be carried out, and the construction time is shortened; 3. the foundation pit does not need to take special water-proof treatments.

Reinforced concrete foundations

Abstract: The present invention relates generally to a reinforced concrete foundation (10) which in this example is a tower foundation for a wind turbine generator (WTG). The WTG foundation comprises a concrete slab (12), and a plurality of tensioned tendons and ground anchors such as (14A) and (16A), respectively. The WTG foundation (10) also includes a mounting element in the form of a cylindrical 'can' (20) which is partly embedded in the concrete slab (12). The can (20) is shaped complementary to and adapted to be welded or otherwise connected to a corresponding bottom portion of the WTG tower (not illustrated).

Combined Measurement of Unknown Foundation Depths and Soil Properties with Nondestructive Evaluation Methods

Abstract: Simultaneously determining both the depth of unknown bridge foundations and the measurement of soil properties along the length of the unknown foundation allows for a more complete and accurate analysis of foundation capacity and scour susceptibility. Foundation depths are measured by the parallel seismic testing method, whereas soil properties are measured with a seismic cone penetrometer. The new combined technique has a great advantage over previous foundation-testing systems in that no borehole is required for either test. Instead, the transducers used to collect all of the required data are mounted together into the same cone probe and pushed into the ground hydraulically from a track-mounted mobile rig. Field testing of the new technique has been carried out and shown that the system is capable of quickly and accurately measuring foundation depths and soil properties on a variety of soil types.

Modeling and simulation for small signal stability analysis of power system containing wind farm

Abstract: To research the stability of interaction between wind farm and power system a mathematical model of wind turbines for small signal stability analysis is presented. A mathematical model of wind power generation sets for small signal stability analysis is established. Using this modeling method two situations are calculated in which the wind power generation sets are connected to infinitive bus system or to three-machine system respectively, and the factors influencing the small signal stability of power system connected with wind farm are researched. The results of simulation show that the oscillation model related to wind turbines possesses good damping coefficient, when the wind turbines are connected with power system the influence of wind farm on other synchronous generators in large power system is considerably weak. This modeling method provides theoretical foundation and a practical tool for the small signal stability analysis of the power system containing wind farm.