Search Documents

By Abhijit Saha

"Two analytical closed-form elastic-rigid-plastic solution methods to predict the rigid foundation behaviour on stone-column reinforced soil are compared, both of which takes into account the stone material yield within the host soil according to stress-dilatancy theory. These are the mechanistic methods developed by the author (2004, 2005) [that presently incorporates the dilatancy angle as per Schanz and Vermeer (1996)] and that developed by Pulko and Majes (2006), that takes into account the column yield as per Rowe dilatancy theory. Since optimal design of stone column necessitates optimum stress concentration on column, which is generally composed of dense gravel with/or without sand, the vertical stress on granular column is often close to its peak strength and the material dilates. To arrive at closed-form analytic solution to this complex soil-stone column interaction problem, some common assumptions like axi-symmetric soilstone column ‘unit-cell’, elastic host soil and rigid-plastic Mohr-Coulomb stone column material are combined with equilibrium and kinematic conditions. The results reflect the beneficial effect of dilatancy within the optimal range or techno-economic domain of area-ratio. The settlement predictions are compared with other analytical methods available in literature as well as with measured settlement reduction of stonecolumn reinforced ground at different subsoil conditions around the globe reported in literature.INTRODUCTIONStone columns or granular piles are frequently used in stabilization of soft clays, silts and loose silty-sands with large amount of fines. The majority of analytical methods assume infinitely wide loaded area with end-bearing columns having constant diameter and spacing that approximate to axi-symmetric conditions, and the approach is known as ‘unit-cell concept’. Several analytical solutions are available, and many of them (Aboshi et al; 1979, Balaam & Booker; 1981) are based on elastic approach considering the stonecolumn and surrounding soil as elastic materials. However, elastic methods give the ratio between the vertical stress in the column to soil (stress concentration factor) approximately equal to the ratio of constrained modulus of both materials. This ratio was found to be considerably higher than measured in the field and it is believed that elastic methods may overestimate the effects of stone columns on settlement reduction (Barksdale & Bachus, 1983). The elastic and elasto-plastic solutions presented by Balaam and Booker (1981, 1985) indicate that the problem can be idealized by assuming that the stone column is in a triaxial state and possibly yielding, such that there is no shear stress at the stone-soil interface and no yielding in the soil. Similar assumptions of stone column to be in a state of limiting equilibrium and under a triaxial stress state are considered in other methods also (Priebe; 1976, Van Impe & De Beer; 1983, Van Impe & Madhav; 1992, Saha & De; 1994, Saha; 2004, 2005, Pulko & Majes; 2006). In majority of the methods it is assumed that under load the stone-column yields at constant volume. However, the last three cases cited consider another parameter; the dilation of stone column. In Van Impe and Madhav’s (1992) and author’s (2004, 2005) method, the dilation is taken into account through the final value of the volumetric strain of column, whereas Pulko & Majes (2006) considered the stone column as Mohr-Coulomb rigid-plastic; dilating at yield in line with Rowe (1962) dilatancy theory."

Jan 1, 2015

By Alper Turan

The use of aggregate pier foundation systems has become widespread as the engineering practice moves towards cost-effective ground improvement solutions that provide accelerated construction schedules. Increased bearing capacity, effective settlement control and potential for liquefaction mitigation are commonly acknowledged benefits of aggregate piers. This paper studies the mechanisms by which aggregate piers interact with each other and with the surrounding ground when excited by seismic loads. A particular emphasis was placed on the response of a raft foundation supported on a site improved using aggregate piers. Three-dimensional nonlinear finite element analyses were conducted using commercial software package, ABAQUS. Non-linear soil behaviour is modelled using a three-dimensional total stress-based bounding surface plasticity model, which is able to simulate stiffness degradation and damping increase in the soil. The soil stratigraphy considered in this study was a 30 m deep soil deposit that comprised a very stiff base layer and a shallow soft surficial clay layer. Ricker Wavelet time histories with different frequency contents are used as the excitation force in the analyses. Various area replacement ratios (ARR) for aggregate piers are studied for a square plan layout. The results presented in this study are considered to be of interest to researchers and designers in evaluating the seismic ground response of the sites improved using aggregate piers.

By Alper Turan, Hesham El Naggar

"The use of aggregate pier foundation systems has become widespread as the engineering practice moves towards cost-effective ground improvement solutions that provide accelerated construction schedules. Increased bearing capacity, effective settlement control and potential for liquefaction mitigation are commonly acknowledged benefits of aggregate piers. This paper studies the mechanisms by which aggregate piers interact with each other and with the surrounding ground when excited by seismic loads. A particular emphasis was placed on the response of a raft foundation supported on a site improved using aggregate piers. Three-dimensional nonlinear finite element analyses were conducted using commercial software package, ABAQUS. Non-linear soil behaviour is modelled using a three-dimensional total stress-based bounding surface plasticity model, which is able to simulate stiffness degradation and damping increase in the soil. The soil stratigraphy considered in this study was a 30 m deep soil deposit that comprised a very stiff base layer and a shallow soft surficial clay layer. Ricker Wavelet time histories with different frequency contents are used as the excitation force in the analyses. Various area replacement ratios (ARR) for aggregate piers are studied for a square plan layout. The results presented in this study are considered to be of interest to researchers and designers in evaluating the seismic ground response of the sites improved using aggregate piers. INTRODUCTIONThe schedule and cost limitations imposed by the traditional over-excavation and replacement method for the stabilization and settlement control for poor soils resulted are underlying factors for the significant increase in the use of aggregate pier foundation system, particularly in the last two decades. Various well known advantages of aggregate pier systems including increased bearing resistance, settlement reduction, and increased uplift capacity have been studied by various authors. The use of aggregate pier systems for settlement control in soft soil deposits was studied by various researchers including Lawton and Fox (1994), Lawton et al. (1994) and Wissmann et al. (2001). Lien and Fox (2001) studied the behaviour of aggregate pier systems supporting embankments and retaining walls. The stabilization of slopes by means of aggregate piers was studied by Lien and Fox (2001), Wissmann et al. (2002). Thompson et al. (2009) reported on a performance monitoring study of aggregate pier systems supporting MSE walls. The interaction mechanism between the aggregate pier system and the surrounding soil attracted attention of various researchers. Handy and White (2006a) and (2006b) studied the changes that occur less than 2 m from centers of the piers, and further away, respectively. The support mechanism of aggregate pier systems subjected to compressive loading were studied experimentally and numerically by White et al. (2007) and Pham and White (2007), respectively."

Jan 1, 2017

By N. Aarthi, G. R. Dodagoudar

The improvement of soft clay deposits using stone columns is a well-established ground improvement technique in the western world. This technique has been well documented and has proper design codes for precise execution in the field. The sand compaction pile (SCP) method is a contemporary technique to stone columns and has limited literature related to the strength characteristics of the loose to medium dense sand deposits treated with SCP. The available studies on the SCPs installed in cohesionless deposits focused on the improvement by indirectly assessing the SPT-N values pre- and post-installation of the SCPs. The widespread implementation of the SCP technique in recent years has increased the need for a more direct evaluation of the improvement. Earlier studies in this regard have revealed that the available design solutions are based on the type of installation equipment, their working efficiency, and accumulated field data. However, it is found that there are no generic design codes for the direct estimation of the ultimate bearing capacity of the SCP improved cohesionless deposits. To meet the design requirement for the SCP treated ground, a series of experimental and numerical investigations are performed in the present study to arrive at a direct framework in the form of design charts based on the pressure-settlement response of the treated ground. The developed design charts give the ultimate bearing capacity (UBC) of the treated sand deposit for the known initial relative density (RD) of the deposit, spacing and diameter of the SCPs, size of the footing, and for the specified target unit weight required for the intended application. It is concluded that the design charts will be of preliminary use to the design engineers to directly evaluate the UBC of the SCP improved loose to medium dense cohesionless deposits as part of the SCP method of ground improvement. It is expected to have more field-scale experiments and in-depth analysis before implementing these charts for actual field execution.

Nov 1, 2022

Technically speaking, the concept of NDT sounds like the "magic bullet" when faced with a questionable drilled shaft. All the Contractor or Engineer needs to do is select an NDT method, apply it, understand the details and extent of the defect and determine whether it will impact the load carrying capacity of the shaft during it’s design life. Unfortunately, it is not that simple. NDT is a tool utilized to indirectly assess the condition of the completed drilled shaft. For the most effective interpretation, NDT data should be correlated with the subsurface information, visual observation, and detailed shaft installation records. The basis for acceptance or rejection of drilled shafts should not be solely based on NDT. The parties responsible for specifying, interpreting and using the NDT results must understand the capabilities and limitations of the method to be utilized, in conjunction with the relevant subsurface conditions of the site, before selecting and specifying a system and acting on the results. This is necessary so that an appropriate NDT method can be specified and contracted. In this manner the results and roles of the responsible parties can be clearly defined.

Jan 1, 2004

By Diego Bellato

Production data recorded by special foundation rigs during construction activities at the site are commonly used for quality assurance / quality control procedures and, in particular, to prove that the installed foundation elements comply with the geometrical and quality requirements defined in the design specifications. Parameters such as crowd force, penetration/withdrawal rate, rotational speed etc. are usually presented in reports in the form of depth and/or time profiles. This type of protocols are already standard QA/QC solutions for ground improvement methods like deep soil mixing or jet-grouting, but they are quite rarely applied in combination with other techniques like diaphragm walls or Kelly drilling. In the latter cases, one of the main reasons behind this lack of site documentation is related to the difficulty in interpreting huge amount of data collected during the creation of single elements, which, in some cases, can last several days (not always in a row). In addition, the building sequence is often characterized by many alternated operations involving different movements of the rig and the use of different tools. In this context, the identification of specific construction activities based only on the mere exam of the time profiles of the recorded production parameters is extremely difficult. In this paper, the time profiles of production parameters obtained from a fully-cased Kelly drilling rig employed on a site in Karlsruhe (Germany) have been investigated and compared with a detailed series of activities deduced from a video filmed during installation. Typical time profile patterns associated to specific procedures have been identified by combining the different information available. The outcome of this study helped project engineers to automatize the recognition of activities directly from production data and led to an overall understanding and optimization of the construction process. INTRODUCTION The special foundation industry is characterized by the use of highly sophisticated machinery for the realization of geotechnical systems such as piled rafts, retaining walls and slabs for excavation pits, cut-off walls for levees and embankments or ground improvement solutions. Rigs can vary in size, weight, and power and can be provided with several drilling tools to cope with the different soil conditions (e.g. clay, sand, rock) and the different geometries of the elements to be built at the site (e.g. micro-piles, large- diameter bored piles, diaphragm walls, anchors). Due to the challenging construction procedures, various types of sensors have started to be mounted on the equipment in the last decades to monitor the behavior of some important machine parameters and to inform rig operators about the on-going process and the status of their devices.

Jan 1, 2019

By Waddah Akili

At an offshore site along the Red Sea coast of Saudi Arabia, marine structures were supported on tubular steel piles driven into coral and coral contaminated sands and silts. Surprises and disappointments faced during the installation of the piled foundation were, to a large measure, due to inappropriate design methodology and absence of proper soil information. The paper describes the design evolution process, highlights the static pile test program conducted to verify design parameters, and amplifies the need to prepare for worst possible scenario when coral deposits are encountered. Despite corrections made to the design, based on site-specific insitu parameters (skin friction, end bearing) perceived from load tests conducted on site; the final design adopted overestimated capacities in over 50 percent of total piles driven. The paper describes the changes introduced to the design during the execution of the project, highlights the pile test program conducted to verify the design, and compares pile design penetration with actual penetration depth. The unpredictable and erratic pile behavior observed, ascertains the need for more appropriate pile design and installation guidelines for driven piles in coral and coral contaminated formations.

By Shawna Munn, Carol Dounitch, Erika Acton

The EQ Bank Tower, a 24-storey office tower with 4 levels of underground parking, is currently under construction at 25 Ontario Street in the downtown core of Toronto, Canada. The tower geometry required an 18 m (60 ft) deep excavation inside an existing 3-storey 100-year-old façade, to be retained in place throughout construction. This presented a variety of design challenges that required several innovations and a customized monitoring program. In this paper, we will discuss two major challenges, and highlight the innovative and adaptable solutions carried out using performance-based design leveraging the observational method. The first was installation of a shoring system in a 500 mm (20 in) gap between the historical façade and a live gas main. The second involved excavating 10 m (33 ft) into expansive shale bedrock adjacent to a sensitive neighbouring building.

Oct 1, 2022

By Narong Thasnanipan

Performance of diameter 1.5 m toe-grouted bored pile founded at depth 44 m in sand-gravel formation of Chiang Mai City is presented in this paper. Toe grouting was applied by using tube-a-manchette method. Effectiveness of toe grouting was observed from the standard penetration tests conducted immediately below pile toe through grouting pipes at two stages, prior to grouting and three weeks after completion of grouting. Improvement of pile end resistance by toe-grouting is demonstrated with a series of back analyses carried out by load-transfer method employing hyperbolic transfer function. Construction experience of large diameter deep-seated bored piles in multi-layered subsoil and practical aspects of toe-grouting are also briefly discussed.

Jan 1, 2002

By Arash Saeidi Rashk Olia, Dunja Perić

The increasing demand for renewable energy has attracted attention to energy geostructures as means of extracting clean geothermal energy from the ground. To further advance the understanding of soilstructure interaction in energy piles analytical solutions considering the self-weight of the pile were derived. These solutions were then incorporated in recently-derived thermomechanical weightless solutions to provide comprehensive analytical solutions for axial displacement, strain and stress in single energy piles. This was accomplished by comparing responses of energy pile under different loading scenarios that reflect presence and absence of the self-weight. Results of mechanics-based analysis revealed that the self-weight of energy piles embedded in stiff soils has no significant contribution to displacement, strain and stress that develop under thermo-mechanical loads. Overall, the significance of the self-weight contribution depends on the magnitude of thermal load as well as the soil-pile interface stiffness. The stiffness of end restraints imposed to the pile head and tip were also found to play an important role in contribution of self-weight in induced thermomechanical stresses in energy piles.

Oct 1, 2022

By Braxton P. Erbe, Douglas C. Brunot

A variety of systems and techniques exist to support deep excavations where sloping is not feasible. This paper will explore an example project involving the use of pre-engineered hydraulic bracing systems to support sheet pile walls. Challenges on site that drove the final design include a high water table, irregular excavation geometry, and underground obstructions. The hydraulic system, connected by pins and not requiring welds, allowed for quick deployment and the modularity to change as required due to unforeseen site conditions.

By Alexander Filotti, Richard Kalson

"In the last decade, the construction industry has witnessed significant changes in the project delivery systems and contractual relationships between the general contractors (GC) and Deep Foundation Specialty Contractors. The Deep Foundation industry, especially including industry specialty subcontractors, have experienced a significant increase in requests that project risks be transferred through contract documents to subcontractors and suppliers with a decrease in margins for the industry. GCs regularly revise their form subcontracts to take into account recent experiences/contractual trends and newly issued judicial precedent, an exercise that is less frequently undertaken by subcontractors and suppliers. These contradictory trends are at the base of the ethical analysis of subcontracts that comprises the subject matter of this paper. Using contracts as a risk management tool in order to mitigate the general contractor’s risks in the context of dynamic changes in the legislative environment will also be addressed. Furthermore, another possibility for risk mitigation for the industry is to actively promote the introduction of the latest technical developments into the contract documents.CONTRACTS’ ETHICSFor thousands of years, ethics have been a constant presence in our lives and have been debated by different branches of philosophy. In modern times, ethics in business started to be an imperative for the success of a globalized economy.“Ethics are standards by which one should act based on values. Values are code beliefs such as duty, honor, and integrity that motivate attitudes and actions.” (Rumbaugh 2004). Some of these values and actions have been carved in legislation in general and in business legislation in particular. More and more, unethical business practices (e.g., corruption) are identified as the root cause of poverty, underdevelopment, and war around the world. In the context of contract ethics, three aspects are of interest:•,Ethics of contract construction•,Ethics of contracting processes•,Ethics of risk allocation in contracts"

Jan 1, 2016

By Andrew Z. Boeckelmann, David S. Graham, Paul J. Axtell

In the last fifteen years, several research studies have evaluated the ability to detect various types of deep foundation concrete integrity flaws with crosshole sonic logging (CSL) and thermal integrity profiling (TIP). This paper synthesizes the findings from the research, focusing on two studies that included CSL and TIP testing of drilled shafts with various types of flaws. The first, a 2016 research study of test shafts for the Wisconsin DOT, included inclusions inside and outside the reinforcing cage, intentional tremie withdrawal during concreting, and soft bottom flaws. The second, a 2021 study of production shafts for the Missouri DOT, included one shaft with and another without soft bottom conditions. After synthesizing the ability of each test method to detect each type of flaw, the paper presents recommendations for improving how CSL and TIP results are evaluated in practice. The recommendations highlight DFI‟s CSL interpretation protocol as well as the importance of evaluating TIP data versus time, not just depth. The paper includes example temperature-versus-time plots for various types of flaws and emphasizes how temperature-versus-time evaluation can be used to distinguish soft bottom conditions from standard bottom-of-shaft temperature roll off.

Oct 1, 2022

By M. Hesham El Naggar, Mehdi Heidari

"Equivalent fixed-base cantilever model is a common approach for performance base seismic design of bridge structures supported by extended pile-shaft. In this method, global displacement ductility factor is related to local curvature ductility demand by assuming a concentrated plastic hinge at location of maximum bending moment. Equivalent plastic hinge length is one of the key parameters that should be assumed accurately in kinematic expression of the cantilever model. Although, some expressions have proposed to estimate the length of the in-ground plastic hinge; however, these relations yield differing results. In this paper, a general expression is derived based on the concept of distributed plasticity to predict the plastic region of yielded piles in clay and sand. A length modification factor is defined to relate the equivalent length of plastic hinge to the real plastic zone. Then, results from nonlinear pushover analyses are used to propose an equation for the modification factor as a function of displacement ductility factor.IntroductionDuring severe earthquake events, development of the plastic hinge in pile foundation below ground level is inevitable for bridge structures supported on extended pile-shafts. A common approach for seismic design of the yielding pile-shafts is to replace the pile-soil system by an equivalent fixed-base cantilever assuming the equivalent system has the same global response as that of the pile-shaft (Budek et al. 2000; Chai 2002). In this method, plastic curvature is concentrated at the center of the equivalent plastic hinge below ground surface. Prior knowledge of plastic-hinge length is essential for proper assessment of assess plastic displacement at the top of the pile-shaft. Unfortunately, existing recommendations for estimating plastichinge length are largely incomplete and/or inadequate.During the last two decades, several relationships have proposed for evaluating the equivalent plastic hinge length, Lp, based on experimental and numerical studies. Budek et al. (2000) conducted numerical modeling to calculate the plastic-hinge length of piles embedded in cohesionless soil. They found that the plastichinge length varies linearly with both soil stiffness and aboveground height, e. Chai and Hutchinson (2002) conducted full-scale experimental tests on reinforced concrete piles in sand. They reported that Lp depends primarily on the aboveground height of the pile, neither sensitive to the soil stiffness nor to the value of displacement ductility factor. They stated that the equivalent plastic hinge length is relatively independent of the displacement ductility factor and is not very sensitive to the change in soil density. On the contrary, Goel (2014) and Liu et al. (2016) conducted nonlinear numerical analyses which revealed that Lp changes with the displacement ductility factor and even suggested that using different values of Lp for different seismic design levels is essential for a reliable estimation of the ductility capacity."

Jan 1, 2017

By Andreas Massarsch

Information Technology, IT, is rapidly affecting all aspects of private life and how professional activities are conducted. Probably the most important development is the Internet, which makes it possible to exchange information independently of time and geographic location. While traditional communication is based on limited availability to information, the basis of the new Information Technology age is abundance and unlimited access. IT has evolved into a powerful resource and new applications are being developed and introduced almost daily. IT influences every aspect of our private life as well as our business environment. If properly used, IT can become an important resource for planning and implementing construction projects more efficiently, at lower cost and with higher quality. Interactive Web Platforms are already being used for group collaboration on a global scale. As these can be used without programming knowledge and are user-friendly, Web Platforms make cooperation more efficient and stimulate members to actively participate. Another application of growing interest are Internet Platforms and electronic publishing, which can provide technical and other information in different formats and much cheaper than conventional books or proceedings.

Jan 1, 2002

By Anthony T. C. Goh, Zhiye Zhao, Laddu B. Jayasinghe, Hongyuan Zhou, Yilin Gui

"Ground vibrations from blasting are undesirable and they are very short in duration with high principal frequencies and high amplitude. Structural response to that kind of excitations may differ significantly from that generated by lower-frequency earthquake vibrations. In practice, the damage to nearby structures to generated ground vibrations has been controlled by various codes and regulations available. However, the existing vibrations limits are not always applicable, as they depend on the geological conditions of the site and the dynamic characteristics of the structure. This paper investigated the influence of the rock-soil interface on the response of pile foundation to ground-borne vibration from rock blasting, through numerical simulations using finite element software LS-DYNA. It is found that the slope of the rock-soil interface greatly influences the location of damage and the extent of damage on the pile. The bottom of the pile is subjected to a larger blast pressure and stresses are highly concentrated at the pile bottom. Thus, the pile bottom can fail in shear before it reaches its plastic moment capacity.INTRODUCTIONDrilling and blasting is the widely accepted method to large-scale rock breaking activities in civil engineering constructions due to its cost effectiveness, higher efficiency and ability to break hard rock. However, ground vibrations from blasting are undesirable and it can cause damage to nearby structures. In practice, the damage to nearby structures to generated ground vibrations has been controlled by various codes and regulations available. The existing vibration limits are not always applicable, as they depend on the geological conditions of the site and dynamic characteristics of the structure.Pile foundations are commonly used as foundations of high-rise buildings and bridges to transfer the heavy loads from the superstructure above through weak compressible soil strata into deeper, competent soil layers which have adequate capacity to carry these loads. In engineering practice, many piles are normally designed to carry mainly vertical loads and very little lateral loads, as typically the vertical loads (the gravity) are significantly larger than the horizontal loads such as wind loading. However, in recent years, there have been a number of reported case studies of translational soil movements that have induced stresses and bending moments that have damaged pile foundations and in some cases resulted in collapse of the superstructure. Typical lateral load include nearby construction activities such as an excavation for a basement or slope, the construction of a road embankment or a tunnel, as well as earthquakes (Abdoun 1997; Goh et al. 1997; 2003; Chen et al. 1999; Dobry et al. 2003; Boulanger et al. 2007; Black et al. 2007)."

Jan 1, 1900

By K. Rainer Massarsch

"Part 1 of 2 By K. Rainer Massarsch, Geo Engineering AB, Stockholm, SwedenINTRODUCTIONConstruction activities, such as driving of piles and sheet piles, soil compaction or excavation generate noise and vibrations. In populated areas these can have a negative impact on the environment, disturb inhabitants and, under unfavorable conditions, cause damage to buildings and installations. This condition is aggravated by the growing public awareness of environmental issues and the increasing use of vibration-sensitive electronic equipment and machinery in industry. In many countries, environmental regulations are enforced more stringently and limit or even prohibit the use of impact or vibratory hammers. This development has restricted the use of cost-effective foundation methods, such as driven and vibrated piles and sheet piles.Vibration problems are gaining importance in many European countries and extensive research has been performed during the past decade, especially with respect to traffic vibrations (Massarsch, 2004). Significant progress has been made owing to the availability of high-quality field measurements and an improved theoretical understanding of how vibrations are generated and transmitted through soil layers. These findings can also be applied to vibration problems associated with construction activities. However, this information is not yet appreciated by the geotechnical profession and even less by the construction industry.This paper discusses the effects of ground vibrations on the surrounding soil and on buildings, with particular emphasis on the different mechanisms of damage that may occur. Guidance is given on the elements which should be taken into account in an assessment of risks associated with piling projects. A simplified method is proposed for assessing the risk of settlements or strength loss in soil deposits. Limiting vibration levels are presented, based on the Swedish standard, which can be used to assess the risk of damage to buildings. Aconcept to predict ground vibrations caused by pile driving and the mechanisms which control the propagation of ground vibrations, will be presented in the second part of this paper."

Jan 1, 2004

By John R. Davie

This paper describes the design and construction of two 5.6 MN capacity drilled piers installed to support the main loading elements of a large cantilevered gantry crane. The critical crane columns were located within and at the edge of an existing sheet-pile cofferdam, which had been filled with loose coal slag when it was originally constructed Due to the presence of the slag and the age and questionable condition of the sheet-piles, the drilled piers were installed to provide vertical and lateral supports for these columns. The lateral capacity of the piers was supplemented by two smaller drilled piers and two large spread footings that were linked by a system of grade beams.

Jan 1, 2006

By David Gatto, Nicolas A. Willig-Friedrich, Jeff A. Segar

"With the increasing demand for electricity, and requirements to generate this power cleanly, more producers are turning towards hydroelectric power. A project in Iowa currently under construction will retrofit an existing Army Corps of Engineers Dam with a hydroelectric generating facility. The design of the intake structure requires the construction of a diaphragm retaining wall. The T-shaped diaphragm wall elements retain an unbalanced fill height up to 21.3 meters (70 feet). The design required a single production element be constructed, tested, and instrumented prior to beginning construction of the rest of the elements. The testing included extensive concrete mix design development, coring, and Cross Hole Sonic Logging. Installed in the other production elements are 10 inclinometers, 4 pressure cells, 4 piezometers, and multiple survey monuments. Some of these instruments require manual readings while most are monitored by an automatic data acquisition system and instantly transferred to a website providing real-time graphical display of the data. This paper will discuss the construction of the diaphragm wall from the contractor’s perspective when working on a site only large enough for two service cranes and a Hydromill excavation unit, without any storage area on the construction pad, describe the testing performed and the quality control procedures employed, and investigate the information gained from the automated instruments providing real time measurement readings.INTRODUCTIONIn 1964 the US Army Corps of Engineers (USACE) constructed a dam by raising the surface grade approximately 34.7 meters (114 feet) above the natural ground line using a combination of fill types. This earthen dam stretched slightly longer than a mile intersecting the flow of the existing Des Moines River. The center of the dam is a concrete spillway consisting of 12 monolith sections. On each end, three of the sections extend 42.6 meters (140 feet) from the spillway to transition from the concrete dam sections to the earthen dam section. Adjacent to these three sections on the East end is where the contractor is actively working, for a private developer under a lease agreement with USACE, on this site to convert it to a Hydroelectric facility licensed for an output of 36.4 megawatts, enough power to meet the needs of about 18,000 homes. To create this, a powerhouse structure, housing two vertical Kaplan turbines is being added to the downstream side of the existing dam. From the power house, two penstock pipes will be cored through the existing concrete monolith sections and connect to the Intake structure on the upstream side of the dam. Protecting and reinforcing the dam adjacent to the intake structure is a new diaphragm wall. This wall is constructed using T-shaped diaphragm elements, acting as a cantilever retaining wall for the intake platform. Figure 1 shows a diagram of the upstream features of the construction."

Jan 1, 2016

By Louay Owaidat

The United States Army Corps of Engineers (USACE) Sacramento District awarded a $64 million construction contract in February 2020 to the Maloney Odin Joint Venture for 3 mi (4.8 km) of levee improvements along the Sacramento River East Levee (SREL). This project kicked off approximately $1.5 billion of work to upgrade levees along the American and Sacramento Rivers and widen the Sacramento Weir and Bypass. The project received the 2021 ASCE Region 9 Project of the Year Award. Contract 1 improved levees along five segments of the river, the longest segment being a 2 mi (3.2 km) reach from Garcia Bend Park to the Freeport Intake Facility in the Pocket neighborhood of Sacramento.

Oct 1, 2022