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By K. Viking

This article deals with some of the civil engineering related problems to be encountered when offshore wind energy projects transform from prototype offshore wind energy converter farms, developed and installed during the 1990?s, to commercial farms that?s currently planned to be built. The offshore wind energy converter (OWEC) installations encounter a wide range of problems, only partial of these are geotechnical. In Europe both onshore and offshore wind farms have, from a historical point of view, usually been founded by using the monopole technique, installed with traditional impact hammers, or by using gravitational foundations. However, the rapid development of bigger turbines and larger wind farms, together with increasing considerations of fatigue aspects, has lead to financial benefits of developing and exploring other foundation techniques. This paper reviews some Scandinavian experiences regarding critical components of the design phase in relation to connecting the superstructure to the ground, and some of the main considerations of how the loads applied to the structure are transferred to the surrounding soil.

Jan 1, 2013

By Emad Farouz

The resistance of very dense glacial outwash formations consisting of sand, gravel and cobble formations can be quite high, and techniques for measuring the strength and deformation properties often cause engineers to underestimate the strength of these layers in drilled shaft design. More realistic measurements of this dense formation can be achieved with slotted steel casing pressuremeter tests. To minimize disturbance and achieve accurate measurements, drilling a pilot hole prior to probe insertion is necessary. Characterizing geologic formations that contain significant amounts of gravel and cobbles is challenging because of scale factor. Inserting a standard pressuremeter probe into this formation without damaging the membrane is difficult. This paper presents a case study for the IR-75 project in Dayton, Ohio, USA, where these dense materials were characterized using a slotted casing pressuremeter, optimizing design by providing more realistic properties of these materials.

Jan 1, 2006

By Colin C. West

On August 7, 1986, Barge 45, while being towed near the mouth of the Niagara River, was swept downstream and pinned against one of the central piers of the Peace Bridge. The barge rested against the pier with 125 feet overlying the Canadian border and 50 feet overlying the American border. The tug boat which was towing the barge was lost further downstream. Fortunately, the crew escaped and were rescued with no loss of life. There was serious concern about the potential erosion effects of the river currents on the foundation of the bridge pier as caused by the flow concentrations around the barge structure. Due to the time of year, with the approaching Fall and associated worsening weather conditions, it was imperative that the barge be removed as soon as possible. Donjon Marine of New Jersey, the United States Navy's Atlantic Zone Contractor, was called on to retrieve the barge. By this time the original owner had abandoned the wreck.

Jan 1, 1987

By Arturo Ressi di Cervia

From the times when men in lacustrine environments drove wooden piles into the mud to elevate their dwellings, until the beginning of the twentieth century builders reacted to the conditions found in the location of their proposed structures by attempting to distribute their loads in ways that could be supported by the foundation's soils; or, if those were unsuitable, by moving the structure, whenever possible. While many major structures were built on stable ground (the pyramids were founded on rock), others were built on [ ]

Jan 1, 2000

By Kenneth Gavin

Design practice for piles installed in Irish glacial till has developed in an ad-hoc manner, based on the results of un-instrumented load tests. This had led to designers using similar design parameters for both CFA and displacement piles. To address the concerns of industry a series of instrumented pile tests were performed by two Irish Universities. These tests summarized herein, revealed that CFA piles develop higher shaft resistance than piles driven in glacial till. However, they exhibit low base stiffness and the end bearing resistance that can be mobilized at acceptable pile settlement is low. The use of simple non-linear elastic design approaches to predict the load-displacement response is considered. The methods are used to predict the capacity of two large diameter CFA piles installed in glacial till. While the predictions were reasonably accurate at predicting the initial load-displacement of the piles, significant creep settlement developed at higher load levels. The cause of the creep settlement was investigated through the use of plate load tests and the consequences for pile design are discussed.

Jan 1, 2009

By Narong Thasnanipan

This paper presents the outcome of the contest on the prediction of the static axial load capacity of diameter 1.20m bored pile founded at 46m below existing ground. The test pile was constructed by wet-processed method and instrumented with vibrating wire strain gauges. Different methods used by the contestants in prediction of load-settlement characteristics are described and compared with actual load test results. Load-displacement behavior of test pile is found to be better than expected. Major difference between prediction and actual test is the higher frictional resistance of Second Sand Layer achieved in the actual load test. The hyperbolic load transfer method used by one of the contestants was applied to back-analyze the load-displacement characteristics of the test pile at different conditions.

Jan 1, 2006

By Dimitris Pachakis

In this paper, the authors give a brief overview of the current practice guidelines and tools for the seismic design of sheet pile quay walls, emphasizing how the design guidelines are lacking when the existing structure performance evaluation is required to meet performance-based criteria. Relying on recent experience they explain how the existing practices can be amended to focus more on performance evaluation as opposed to design. An example is given of an old sheet pile quay wall analyzed and evaluated for its performance according the recent performance criteria devised for Californian Marine Oil Terminals.

Jan 1, 2011

By Narong Thasnanipan

In Bangkok due to the prevailing condition of subsoil (existence of considerably weak stratum at top part) deep-seated large diameter bored piles of over 50 m depth with 0.8 -1.8m in diameter have been mainly used for heavy structures such as high rise buildings, elevated expressways, flyovers and more recently for underground subway stations of the first Bangkok MRTA system. As a part of pre-planned quality assurance regime and retrospective investigation, integrity of the piles are tested to obtain the information with regard to the potential deficiencies of the constructed piles which may have formed during pile construction process or may have been attributed by other activities after construction of the piles. An overview of three commonly used non-destructive tests such as sonic integrity, sonic logging and high strain dynamic load tests on deep-seated piles in Bangkok subsoil is presented in this paper. Advantages and limitations of each integrity test are discussed.

Jan 1, 2004

By Richard J. Finno

This paper presents an overview of methods that can be used to predict damage to buildings as a result of excavation-induced ground movements and describes an adaptive management approach for predicting, monitoring, and controlling excavation-induced ground movements. Successful updating of performance predictions depends equally on reasonable numerical simulations of performance, the type of monitoring data used as observations, and the optimization techniques used to minimize the difference between predictions and observed performance. This paper summarizes each of these factors and emphasizes their inter-dependence. Case studies are presented to illustrate the capabilities of this approach. Examples are given to show how optimized parameters based upon data obtained at early stages of excavation can be used to predict performance at latter stages, and how they can be applied to other excavations in similar geologic conditions.

Jan 1, 2010

By Steven R. Musselman

The bending strength and flexural stiffness of a micropile at its threaded connection is less than its intact strength and may fail due to thread slippage or by fracture through the pin (reduced cross-sectional area of male threads in the threaded zone of the casing). The mode of failure depends on the reduction in cross-section necessary for machining the threads, and details of the threaded connection such as the length of threaded connection, size and shape of threads, and the thread density (threads per inch). Based on data from bending tests conducted on 9-5/8 inch diameter micropile casing, a method has been developed to predict the ultimate moment capacity and initial bending stiffness of round threaded micropile connections. Two modes of failure were observed from four-point bending tests conducted at the University of Illinois on 9-5/8 inch casing with round threads. Threaded micropile casing connections with an effective thread length of 1.35 inches typically failed by slippage at the threads (jump out), while connections using an effective thread length of 1.89 inches failed by fracture of the pin. These two failure modes were described by W.O. Clinedinst in his report to the American Petroleum Institute on tension tests of threaded pipe casing. Clinedinst developed an empirical formula to determine the tensile strength of threaded connections. A method to predict moment capacity for threaded micropile connections by modeling the micropile cross-section and applying Clinedinst?s equation to determine the max tensile stress along the threaded connection while satisfying force equilibrium is proposed. The predicted moment capacity for threaded connections using this approach is within ten percent of measured for both modes of failure observed from the bending tests.

Jan 1, 2007

By Richard Deakin

This case study describes aspects of the design of bridge foundations using 320mm diameter steel tube piles in the vicinity of Montréal, Canada. In this area, these piles are a very commonly used and cost effective solution for deep foundations. Typically they are driven through thick Champlain Sea Clay to bear onto stiff, strong rock. However, in some locations there is a layer of glacial till between the base of the clay and the rock which cannot always be fully penetrated by the piles. There is currently little published information, about the bearing capacity of these piles in the local till, and this paper presents and discusses some pile-test data from a recent project. The nature of the glacial deposits in the study area is presented using information gained from published geological data, the project ground investigations and site observations. The design approach and assumptions are discussed, together with the aims and outcomes of preliminary field driving trials and pile tests. The paper then discusses the results of dynamic tests undertaken on production piles. Bearing capacity factors are back analysed from the dynamic test results and compared against values assumed within the design. Observations are made that designers of future foundations in similar conditions may find informative.

Jan 1, 2011

By Hanlong Liu

The construction process and load-bearing behaviors of Cast-in-place Concrete Thin-wall Pipe Piles are analyzed based on its application on Yan-Tong Expressway project. The low strain test, static load test and field excavation are also carried out. It can be concluded that the new type of pile is convenient to construction with high bearing capacity and reliable quality, which has great potential in practical engineering.

Jan 1, 2006

By Issa S. Oweis

Limestone is a sedimentary rock composed primarily of calcite (calcium carbonate). In the presence of an aqueous solution of carbon dioxide (carbonic acid) bicarbonate radicals (2HCO3)- are produced that are highly soluble. The same type of reactions occur in terrains where dolomite (calcium magnesium bicarbonate) reacts with carbonic acid to produce highly soluble bicarbonates (4HCO3)-. The source of carbon dioxide is the small content in rainfall but to a large extent from the organics in the soil. The solution activity depends on many factors including the content of carbon in the rock, acidity of soil water, groundwater velocity and other factors. The resulting features are referred to in literature as sinkholes, solution channels, caves, karstic topography, and cavernous limestone. The presence of solution features affect the shafts in several ways: (a) the shaft resistance is affected by voids along the shaft, (b) concreting of the shaft should consider the presence of voids along the shaft, and (c) the shaft base may be in close proximity to a solution feature that may cause future collapse under structural loads. Methods to mitigate such effects include verification of rock to below the base (vertically and laterally). Cavities are stable by virtue of arching in the rock. Under the action of end bearing from a shaft, the arch may collapse depending on its proximity to the base of the shaft and the strength of the rock. This paper focuses on this issue. Finite Element analyses are conducted to relate shaft end load and bearing area that will produce failure based on given rock properties, size and location of cavity. Failure is defined as settlement of the base equivalent to 5% of shaft socket diameter. The software Plaxis is used for analysis. The rock is considered as c-f material derived based on Hoek-Brown failure criteria (2002 edition) that is based on Geological Strength Index (GSI).

Jan 1, 2009

By J. Matos e Silva

"Abstract The paper refers five examples of executed diaphragm walls with one to five levels of anchorages. For each example a comparison is made between the results of the design using the traditional criteria and the ones obtained by using the Eurocode 7 and the Portuguese Norm related to the EC7 (NP EN 1997-1 2010), as the Eurocodes consider the possibility of each European country to adopt their own geotechnical parameters as these may vary from one country to another. A comparison is also made with the behaviour of these diaphragm walls during its construction phase; so the values from the design that were adopted in the construction are listed in tables 2 to 6 in the “Construction Options” columns. From the referred examples the author presents his conclusions.1 - INTRODUCTIONIn the so-called “traditional criteria” the soil parameters (dry unit weight, angle of internal friction and cohesion) have values obtained through tests or empirically. It is assumed that the characteristic values of the soil parameters adopted in Eurocode 7 are equal to the soil parameters adopted in the calculations by the “traditional criteria”. In the present paper the design according to the EC7 was made considering only the ultimate limit states and the respective Cases A1 and A2.The partial coefficients used for the actions in the present paper were those on Table 1:2 - CONSIDERED EXAMPLESThe five examples correspond to the situations of figures 1 to 5, and the respective results are summarized in tables 2 to 6.For all the considered examples, that are case histories, a simplified method published by Matos e Silva (March 2000) was adopted. This method attains good performances when compared with other more sophisticated ones as the finite elements and the elasto-plastic methods as described in a paper published by Matos e Silva (2000). All the obtained values were compared between them and with the so-called “Construction Options” that were the values adopted by the designers of the considered examples. For the wall bottom length calculation two possible situations were envisaged:"

Jan 1, 2014

By Timothy D. Stark

Jet grouting has increasingly become one of the ground improvement technologies used to address seepage concerns and to provide strength improvement of soils. The technique of jet grouting uses high pressure/velocity jet fluids to erode the existing soil and then to mix the cuttings with cement slurry to form soilcrete. Excess slurry or spoil is ejected to the surface. If the native soil is not completely mixed with slurry, the resulting columns will have soil inclusions which can reduce the strength of the column and/or increase the permeability of the column. A jet grout test program at Tuttle Creek Dam shows that the completed large diameter columns contain perhaps 40 to 50% or more of native soil that was not broken up and mixed during the jet grout process. The test program included excavation of full-scale columns to a depth of 35 ft (10.7 m) for visual inspection and testing. Additionally, six of the columns were cut or sectioned to investigate the interior of the columns. The observed inclusions include significant amounts of both fine grained (silts and clays) and coarse grained (fine sands and sands) soils. Evidence suggests at least two explanations: (1) fine grained soils can be difficult to erode and break up into small enough particles that can be ejected to the surface, especially if at low natural water content, and (2) when large diameter columns are being excavated, the excavated roof of the cylindrical cavity may be unstable and may collapse. With this roof instability large slabs of material can break off, fall into the slurry and escape the cutting and mixing action of the rotating jets. This paper describes the Tuttle Creek Dam test program, inclusions observed in the completed columns, and suggests potential causes of the inclusions.

Jan 1, 2009

By Robb L. Swenson

Construction of foundations for the Skyway Segment of the San Francisco Oakland Bay Bridge required innovative techniques due to the mass of the structures being inserted and the unique subsurface of the Bay. Twenty of the pier structures required large sheet pile cofferdams. Eight other foundations were installed in open water without cofferdams at the deeper part of the Bay. This narrative will present the initial planning, as well as the stages of installation, for each type of foundation. The first section will discuss foundation constructability modifications made during the initial planning phases of the project. Considerable effort was expended by Caltrans, the owner, T.Y. Lin the designer, and KFM (Kiewit/FCI/Manson) the contractor in modifying the design to assure that required tolerance would be maintained during the installation of the foundations. The final section will describe the steps required for installation including: initial access dredging, installation of cofferdams, preparation required to install the footing boxes, footing box installation, foundation support pile installation, and pile to box connections.

Jan 1, 2005

By Larry Rayburn

Design of cost effective engineered solutions to complex problems requires the team efforts of the owner, the designer and the specialty construction contractor. The basic ingredients of success required to remain competitive and still produce a quality product are creative design based on experience and sound engineering principles, plus practical aspects of constructibility. The three case histories describe creative design/construct approaches that benefited all parties. 1. Introduction The increasing demand placed on specialty contractors to provide cost effective buildable solutions to complex construction problems compels us in the industry to be highly innovative. The practice of geotechnical engineering is considered more of an "art" than perhaps the other disciplines within civil engineering largely because of the basic nature and variability of soil and rock. The geotechnical design engineer must have the knowledge of the components of his design and know the limitations of his equipment and labor force. Thus, for the design/build specialty contractor the potential for creation of unusual solutions to difficult problems is quite high.

Jan 1, 1991

By Bill Starke

The acceptance of AugerCast piles in Canada has been limited. Many engineers are apprehensive about the quality of the piles produced by this method. However, advances in the sensing instruments and computer technology can now provide satisfactory levels of quality assurance. Post construction tests such as the sonic echo method can give an indication of pile shaft integrity. Computerized monitoring of the pile installation process is an immediate and more positive method of quality assurance. The computer continuously measures and records the parameters which indicate the quality of the pile. If these parameters do not indicate a satisfactory pile, it is replaced before the concrete hardens. Computerized monitoring of the installation process is another tool available to the engineer. The data from this system analyzed with soil borings, site inspections, and possibly sonic tests can provide the engineer with enough information for pile certification.

Jan 1, 1997

By Zhang Jiaju

For the highrise buildings with deep foundstion of irregular plane shape, an appropriate calculate model to the heave of foundation soil after excavation is proposed and studied using analytic method and FEM (Finite Element Method) respectively to provide an effective way for solving this kind engineering problem. Also combined with the practice of construction deep foundation of Capital Mansion, calculation of the heave of foundation soil after excavation is given. Compared these results from above two methods with the results measured in situ, it is conformal on the whole, and the results by FEM are much closer with the measured.

Jan 1, 1991

By Joanna Bzówka

Nowadays, there are some new requirements for the supermarket floors. The floors are loaded by high point- and moving-loads. In spite of this fact, it is necessary to ensure the stiffness of the floor and the stiffness of its support. When pile foundations are designed in the case of weak soil, the piles are recommended under the foundations of the supermarket and also under the floor layers. The example of foundation of a typical supermarket located on long­standing municipal dumping ground is presented. Indirect foundation - CFA piles, 0.5 m in diameter and 4.5 to 20.0 m long, was de­signed. Fifteen trial loading tests were carried out.

Jan 1, 2006