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By Sherif Elfass, Gary Norris

Bi-directional load testing of drilled shafts has been widely adopted as a means to evaluate their load carrying capacity. However, in order to reach failure, most of these tests are carried out on sacrificial shafts using expensive sacrificial elements such as hydraulic jacks. A proposed low-cost bi-directional testing technique is discussed. It mechanically loads the end bearing soil below a drilled shaft, against its side shear resistance. The technique was originally established as an alternative to post-grouting to reliably account for the forfeited end bearing resistance. However, since it loads the shaft in a manner similar to conventional bi-directional tests, it can be used to not only load test sacrificial shafts, but production shafts as well. Furthermore, unlike conventional bi-directional load tests, the load is applied through surface jacks. These jacks, along with other load test components, are movable and can be reused to load test all the shafts of the project thus presenting an economic benefit. The concept of this technique has received favorable feedback from a few consulted departments of transportation, and while promising, has not been field tested to date. A U.S. patent was issued for the tip loading module and the loading technique described.

Sep 8, 2021

By Maral Papazian Bedian

"Case 2. 100th Street Bus Depot: Elimination of Deep Caissons in Favor of Spread FootingsThe PROJECTThe 100th Street Bus Depot is a new five-story bus terminal for the New York City Metropolitan Transit Authority occupying one city block in Manhattan between 99th and 100th Streets, and between Lexington and Park Avenues. It replaces a former two-story garage, built in the 1890’s and initially used as a trolley-car barn. The new structure is a steelframed building with concrete floors and includes a partial basement near its middle. The easternmost column line with design loads of 10 MN (1,125 tons) is within 1.5 m of the underlying multi-tube Lexington Avenue subway system. To support the new columns along the subway line, the project bid plans had called for 1 m diameter and 17 m deep drilled shafts. The upper 14 m of each unit would have required 50 mm separation from the surrounding rock to prevent stress from being imposed on the roof and walls of the adjacent tunnel. The column loads were thus transferred to below the base of the tunnel and supported by 3 m long sockets in bedrock. The bid documents contained extensive test boring information, which revealed that the project site was underlain by massive Manhattan Mica Schist bedrock within just 3 m below street level. In fact, the Lexington Avenue two-level and multi-tube subway had been tunneled through this rock circa 1910, leaving an about 6 m thick solid roof over the upper-level subway. The NX rock core recovery values were near 100 %, with average RQD of 75 %.The CHANGEThe Bus Depot project was let as a design/build contract with a very aggressive fast-track schedule. Both the pre-bid preliminary design and the subsequent final design by the Contractor’s own hired design engineers relied heavily on very restrictive codes, including unnecessarily conservative approaches to seismic design. Any suggestion for value engineering change was undesirable and was strongly resisted. Yet, objecting against the blind reliance on codes in foundation design, the author questioned the real need for the deep drilled shafts to support the columns along the subway. The unsupported statement that no stresses from the new structure can be imposed on the roof and walls of the adjacent tunnel was not sufficient reason for the drilled-shaft design. Unconvinced that deep shafts were necessary, the author rushed to MTA’s warehouse where many rows of rock core boxes were neatly stacked. Careful inspection and some simple testing of the rock cores with the blows of a geologic hammer gave support to the reservations about the design. Later, as expected, the schist bedrock at this site was found to be hard to very hard with unconfined compressive strength values estimated to range from at least 70 MPa to over 100 MPa (10,000 psi to 15,000 psi). The tensile strength of the rock was assessed to be minimum 5 MPa (750 psi)."

Jan 1, 2003

By Ramin Motamed, Fahim M. Bhuiyan, Raj V. Siddharthan

Numerical lateral load analysis based on the beam on Winkler foundation (BNWF) model (i.e., the p-y method) is a simple, and widely used tool to predict lateral responses of drilled shafts from field load tests. The lack of a site-specific p-y model for cemented soil layers such as caliche is one of the major limitations of simulating lateral load tests conducted in Las Vegas Valley. In this study, some of the existing p-y models for rock materials, such as Florida Limestone and Vuggy Limestone have been evaluated to simulate the lateral resistance of caliche. This has been done in the context of four lateral load tests in caliche-dominant sites from the recently constructed Raiders Stadium project in Las Vegas (NV). The uncertainty in characterizing the material properties of caliche has been addressed. The p-y analyses were performed using NVShaft, a MATLAB-based, comprehensive load analysis program. The applicability of the considered p-y models for caliche material was evaluated by quantifying the normalized error margins between measured and predicted lateral responses from the simulations of the mentioned load tests. Correlations between such errors and the depth and thickness of caliche in soil layers affecting numerical predictions were established, for both up to and beyond design load levels.

Oct 1, 2022

By Michael W. Neill, O&apos

The performance of foundations that combine the high bearing capacity of rafts (mats) with the settlement reduction capability of piles is described through a summary of 24 case histories. Structures included are high-rise commercial office buildings, governmental buildings, industrial facilities and residential buildings, and subsurface conditions range from soft clay to stiff soil overlying rock. Pile types are bored, augered and driven. Since piled rafts are not commonly used in the United States, most of the case histories are from overseas. In all cases the performance of the foundations was monitored during and after construction. Particular emphasis is placed on measured settlements of the piled-raft foundations, distribution of resistance between piles and raft, and general analysis methods that were used by the designers for various geotechnical circumstances. Finally, patterns of behavior are summarized. In most cases, the piles were not designed to mobilize their full capacities under sustained loading of the foundation; therefore, under long-term loading conditions, the piles typically carried more load than the raft. This paper is the result of a study conducted by ITC-18 (Deep Foundations, Willem Van Impe, Chair) of the International Society for Soil Mechanics and Geotechnical Engineering by a subcommittee chaired by the author.

Jan 1, 2003

By Kirty Dave

Foundations in any contract are the most uncertain parts of the contract and most of the "Construction-Contract-Disputes" are either directly related to foundations or arise as 'Side-effects of changes in promises related to foundations. Foundation Engineering is defined as ' The art of selection, designing and constructing the elements that transfer the weight of structure to the underlying Soil or Rock." (Ralph B. Perk). This art started becoming a science since 1920, when scientific efforts to determine the behaviour of sub-surface materials were made. The art and science merged to give new techniques and the science started dominating the field as more and more refinement came in techniques to predict more accurately the characteristics of the sub-surface elements. Inspite of good thorough investigations and design, the contractual promises drafted could leave some room for differences between the parties and above all the prudency expected of both the parties may fall short of the expectations raised in the contract. This may give rise to disputes which may need to be resolved as per principles of law. This paper attempts to initiate a dialogue amongst Foundations-Engineers and Contractors as to how do we minimise the differences arising out of or related to contracts concerning "Foundations".

Jan 1, 1996

By Robert S. Thomas, Bernard M. Tarralle, Nasser Massoudi

"The Commonwealth of Virginia is restoring and expanding its Capitol of great historic significance. Designed by Thomas Jefferson in 1785, it is the second oldest Capitol building in the United States. The building expansion required excavations immediately adjacent to its South Portico. The building, which rests on shallow brick footings, is very sensitive to any disturbance caused by construction and excavation. A comprehensive and secure plan of operations was devised by the design team to ensure that this national monument remains unharmed by the new construction. Various construction techniques were implemented to satisfy the strict movement goal of 0.25 inch and distortion of U2000. They consisted of jet grout columns to stabilize the upper soils, compensation grouting for future foundation leveling, a tied-back reinforced concrete diaphragm wall for excavation retention and foundations, and realtime instrumentation for monitoring. This paper describes the design approach for the retention system, providing information on the various construction phases and techn iques, and reports on the movements recorded by the real-time monitoring system during the course of the project. At the time of this manuscript preparation, and the deep excavation complete to final grade, the results indicate that the extremely restrictive building movement criteria have been met. The success can be credited to detailed design, close cooperation among the project team, prudent construction methods, and real-time monitoring. INTRODUCTIONThe Commonwealth of Virginia is undertaking a comprehensive renovation and expansion of the Virginia Capitol building located in Richmond, Virginia. The Capitol building was designed by Thomas Jefferson in 1785, with construction of the original building starting the same year. The Capitol building was designated a National Historic Landmark in 1960 and was listed on the National Register of Historic Places in 1966.A part of the comprehensive renovation and expansion of the Capitol is a 25,000-square foot, two-level subterranean extension on the south side of the Capitol building, which will serve as a new Visitor Center and public entrance for the Capitol. Deep excavations were required for the construction of the new Visitor Center. The excavation required a permanent retention system to accommodate an approximately 40- foot deep excavation."

Jan 1, 2005

By Franz-Werner Gerressen

New developments are required each day as our industry becomes more competitive. To improve performance, continue and to ensure future demands can be met. This requires the development of technical support systems that enable a more constant delivery and quality of installation of pile foundations and other applications. For example: assistance systems capable of relieving the machine operator of automating monotonous or repetitive operations. Real time installation control of the production process to manage quality control, or data transfer and reporting systems capable of keeping pace with the digital future. This paper will describe these new approaches and considerations required for these new developments. The paper also describes the equipment which is needed to execute the work under the various conditions and provides references herein. INTRODUCTION The success of a construction site is influenced by a number of factors. Selecting the most efficient and economic methods during the planning phase to defining the right direction. This means having multifunctional equipment available. To ease the usage of this equipment by the operator, uniform operation and control systems are essential. Systems like this can provide uniform handling procedure for more than 20 different installation techniques. Experienced operators are not always available. Therefore, to ease the start for beginners and to support training, numerous assistance systems were developed. This ranges from simple information for controls shown on the monitor avoiding misuse to systems which can partly automate the construction process. Regardless, the best equipment is not enough when the construction is not running smooth. The control system not only helps to organize and coordinate service of the equipment; moreover, it allows the operator to control the quality during the installation process reacting if needed. It allows process optimization as well as documentation which might be required for later negotiations.

Jan 1, 2019

By Juhyung Lee

Numerical analyses were performed to analyze the behavior of two different type of suction piles (mono type and group type) under various soil layer conditions (uniform silty clay layer, uniform silty sand layer, and two-layer deposit consisting of clay and sand layers) and lateral loading locations (top, middle, and bottom of the suction pile). According to the results, mono suction pile shows maximum resistance when load is applied on its middle, regardless of the soil layer conditions, while group suction piles varies significantly according to the allowance on head rotation. When head rotation is allowed, the behavior of group type piles become similar to the behavior of mono suction pile. Whereas, when rotation is prevented, resistance is maximized when load is applied on the top head. Moreover, group suction piles show higher efficiency regardless of the ground condition and geological stratum. For further advances, concrete block on the top of group suction piles are suggested as an effective alternative method to prevent partial rotation and maximize ground resistance for group suction piles.

By Danny Déry-Chamberland, Peter Bowman, Michael Byle

"The Barrage des Quinze dam is a concrete sluice dam consisting of 19 spillway sections, each of which is approximately 7.6 metres wide and 14.5 metres deep. Rehabilitation efforts being performed on the dam including demolition and improvement of the roadway and spillway sections and grouting to mitigate underseepage. Initially, conventional cement grouting was attempted and was successful in 14 of the spillway sections, but unsuccessful in 5 of the sections due to the high water flows which washed the grout away. The removal of the roadway and portions of the piers during construction temporarily reduced the stability of the structure limiting grouting pressures that could be applied. This and the substantial high water flows (leakage) beneath the dam between the concrete/rock contact and within fractures in the upper rock formation created a challenging situation to create a cutoff.A grouting solution was developed that involved implementing several different grouting methods and materials including balanced high mobility grouts (HMG); low mobility grouts (LMG); polyurethane grouts; and sodium silicates. Because of the critical scheduling for the work, multiple approaches were planned and made available on site so that the work could proceed with the best technology with little, if any, time loss. The end goal of the grouting program was to create a seepage cutoff beneath the 5 sections of the dam in a stepwise process. The initial step was to fill the large openings and create a grout barrier to reduce the high water flow. The second step was to seal the contact between the base of the dam and the bedrock; and the third step was to complete closure by grouting a deep grout curtain into the underlying rock. Other features of the work included an extensive grout mix testing program, water pressure testing, borehole camera survey, and monitoring of the grout injections."

Jan 1, 2016

By Filippo Maria Leoni, Wesley Schmutzler

"Deep Mixing Method (DMM) for the Rio Puerto Nuevo Project in San Juan was chosen by the Corps of Engineers to improve the soils adjacent to a 90 inch forced sewer main relocation and to improve the soils for the base of a new drainage channel. The project is located just east of San Juan and south of the Horizon Port. The soils to be improved consisted of fill, marine clay, organics (peat) and the foundation clay layer. A preconstruction soil investigation campaign was performed to assess soil properties and to retrieve samples of the different soil layers for the laboratory Bench Scale Testing program (BST). The BST was conducted using various binder contents and water/cement ratios in each of the soil types; the selection of the different combinations and dosages was based on past extensive experiences on similar materials. Following the laboratory program, a full scale Field Test (FT) was done installing several DMM elements to verify the results of the BST and fine tune the construction parameters. Each element consisted of two 5.5 feet diameter overlapping mixing augers installed simultaneously to a depth of approximately 60 feet using a SOILMEC SR-90 dual axis drilling rig. The FT construction and post-construction coring results showed significant differences between the lab study and the actual field conditions. This paper will highlight these differences and the importance of performing both pre-construction laboratory and field tests in order to ascertain the proper mixing parameters in the different soil layers.IntroductionThe Puerto Nuevo project consists of the stabilization of a major drainage channel using Deep Mixing Method (DMM) and the relocation of a 90 inch forced main sanitary sewer outfall. The first portion of this project was a 40 x 16 x 2,000 foot box culvert installed in 2004. In order for the drainage system to be completed and function properly, the 90 inch forced main needed to be lowered about 20 feet to allow for proper drainage.DMM was chosen by the US Army corps of Engineers to stabilize the drainage channel as well as improve the soil under the relocated sewer main. The overall layout of the project is shown in Figure 1. The DMM is arranged in different zones (A through E) with variable top and bottom design elevations as can be seen in the typical cross section for ZONE A and B as an example. (Figure 2) The total amount of soils to be treated by DMM is approximately 84,000 cubic yards up to a maximum depth of 57 feet from ground surface and an Area Replacement Ratio of 100%.The equipment used to perform the DMM is a Soilmec SR90 twin-shaft jet assisted deep mixing rig (Figure 3) coupled with a LODOS 30 grout plant and two Soilmec 7T-500J high pressure pumps."

Jan 1, 2015

By Peter Smith

One New Change is a landmark retail / commercial development in the City of London. Integral to the structure is the three double storey basement from which the building is serviced. The building construction involved a ?top down? (up down) construction technique to give programme benefits. In addition, the planning authority stipulated that 10% of the energy demand had to be met by Renewable technology. Cementation Skanska has not only delivered the foundation package - comprising secant piling and foundation bearing piles including Cemloc® plunged columns - but, alongside subcontractor Geothermal International, also installed a 1.7MW ground source heating and cooling system using Energy Piles® and open?loop wells to provide the renewable energy. The works were successfully installed and completed within a tight programme, and within the logistical constraints imposed by an inner-city location, concurrent demolition works and multi contractor involvement in the basement construction.

Jan 1, 2010

By Richard Guenther

As available space in urban centers becomes more scarce, builders and developers are increasingly turning to vacant, existing structures to meet cities' growing needs. The developers of City Ridge Roadside Development and North America Sekisui House (NASH) - - found a suitable site for their "urban village" at the former Fannie Mae headquarters complex on Wisconsin Ave. NW in Washington, D.C., which had been vacated in early 2018. The urban village will consist of eight new structures centered around the building that currently sits on the site. All told, the project will include 687 residential units, a 150-room hotel, over 150,000 sq ft (13,935 sq m) of retail space, and 62,000 sq ft (5,760 sq m) of office space. A below-grade parking structure will extend across most of the footprint. The Fannie Mae building, which was designed in the Colonial Revival style to mimic the Governor's Palace in Williamsburg, Virginia, was named a historical landmark following a request from the development team. The central portion of its existing masonry structure was built in 1956 on pile caps with small-diameter cast-in-place piles. Two wings, which were added in 1962, were built on belled caissons. There are three levels above grade and one below.

Feb 1, 2022

By Bernard H. Hertlein

The introduction of LRFD methods for structural design has been a gradual process by AASHTO, ACI, AISC, ASCE, and the FHWA, which has largely been ignored by the deep foundations industry. In 2007, however, the industry has been obliged to embrace LRFD for any deep foundations on projects involving federal funds. The authors are concerned that the risks caused by the need for, and the difficulty of providing, reliable quality assurance, will result in unnecessarily high safety factors that will defeat part of the purpose of LRFD. A primary attraction of LRFD for owners and engineers alike is that it promises more efficient design, and therefore cost reductions. Unfortunately, a key element of LRFD philosophy is often overlooked - that the applied safety factors can be rationally reduced, often allowing less material to be used, thus saving costs, but only if all the risk factors involved are identified and closely controlled. This means that both the quality of the materials and the quality of the construction work must be adequately monitored, and held to an acceptable standard. In the case of deep foundations, the soil in which the foundation is constructed is also a critical component that must be taken into account in the assessment of risk factors.

Jan 1, 2007

By Richard Schmidt, Lijun Deng, Mohamed Abdelaziz, Weidong Li

Helical piles are widely used as a foundation supporting a variety of different structures. Understanding the axial behaviour of helical piles is required to confirm the engineering design. Helical pile research is often conducted in the field, but this method can be prohibitively expensive in some cases. Geotechnical centrifuge modeling offers an alternative method for the helical pile research and practice. A series of axial load tests of helical piles installed into cohesive soils were conducted on the geotechnical centrifuge at the University of Alberta. The objective was to investigate the effects of inter-helix spacing and soil strength on the axial behaviour of helical piles. Four types of aluminum model helical piles including one single-helix pile and three double-helix piles with various inter-helix spacing ratios were tested. Both compressive and tensile loading tests were conducted. All model piles were instrumented with multiple strain gauge stations. The clay had an undrained shear strength of approximately 50 kPa and 120 kPa. The test results indicate that there is a transitional failure mode between the two widely recognized failure modes, i.e., individual plate bearing and cylindrical shearing. The shaft adhesion was significantly reduced by the helix. Axial capacities were comparable to the field test results.

By Donald T. Robertson, Kurt Hecht, Michael K. Muchard

"This paper presents case histories of driven concrete pile damage detected with dynamic testing methods utilizing strain gages and accelerometers embedded in the pile at the prestressing yard during pile construction. Data from the embedded instrumentation is compared with data taken with external bolt on instrumentation and other test methods such as low strain testing on the same pile. In the most severe cases, the piles were extracted revealing and corroborating the embedded data collector results.INTRODUCTIONDynamic testing of driven pile foundations was originally developed in the late 1960’s and commercialized in the early 1970’s. While the methods of analyzing dynamic test data have improved with the advancement of computer technology, the test method and the sensors used to acquire the data have changed little. In 1998, under a research grant provided by the Florida Department of Transportation, (McVay et al, 2002) an Embedded Data Collector system (EDC) was developed. The collector utilizes two sensor packs, each consisting of one strain gage and one accelerometer, embedded near the pile toe and pile top. Utilizing the toe sensor pack, the system provides reliable real time pile end bearing capacity measurements. This end bearing capacity is combined with a Case Method Solution augmented with an automatic damping calculation to provide the overall pile capacity, pile skin friction capacity and pile end bearing capacity. Also, since the gages are embedded, they have the ability to track all changes from the casting yard (i.e. prestress), driving, and subsequent setup (freeze, relaxation, etc) at both the top and bottom of the pile."

Jan 1, 2017

By Leonhard Weixler, Alexander Blatt, Franz-Werner Gerressen

Diaphragm wall technique is usually used to construct structural elements in the ground, commonly used for retention systems, permanent foundation elements or deep ground-water barriers, named Cut-Off-Walls (COW). It can be anticipated that global urbanization and increasing demands on environmental considerations will need to be accommodated in underground space in the future. These trends show an increasing requirement for diaphragm walling in even more complex conditions, especially in inner-city applications with limited space. Therefore, there is the demand to minimize the size of equipment to accommodate such projects. Following this demand, a new trench cutter system, the so-called CUBE System, was recently developed. The complete trench cutter system has been fit into container size dimensions so that it can work in very limited space conditions. In addition, complex conditions in terms of space limitations require specifically adapted solutions for slurry, spoil, reinforcement and concrete handling and the related logistics to ensure smooth production. Due to the limited space requirements, the impact on the surrounding environment is limited. As the system is electric driven, an additional reduction of carbon footprint can be expected. First tests of the system have been carried out and the results will be shared. The paper will explain the construction process and the specific challenges and experiences made for these extreme conditions.

Oct 1, 2022

By Franz-Werner Gerressen

As alternative energy industries pick up speed internationally, and as government regulation and restriction limit the use of impact hammers due to environmental limitation from construction induced noise during pile driving operations, unconventional solutions for more complex offshore foundation installations have become a necessity. Manufacturers and equipment suppliers race to develop alternative techniques to accommodate for offshore foundation construction in various soil conditions and at greater water depth. The FLYDRILL, and the Seabed-Drill BSD are two innovative systems for the installation of offshore monopiles with reduced environmental impact

By Emre Biringen

Over the past decades, there has been an increasing recognition of the strategic use of pile-supported rafts in design of heavily-loaded structures to reduce total and differential settlements. However, such a hybrid foundation construction method has not been widely utilized in many countries, including the U.S., due to code limitations. In current practice, the foundation design is based on either (i) the bearing capacity of the raft supported by the subgrade soils, or (ii) solely the pile capacity. This paper addresses the potential use of such hybrid piled-raft systems, where the structural load is shared by both by the piles and the subgrade soils directly beneath the raft, in foundation design of power plant structures. The study assessed some of the characteristics of piled-raft behavior by undertaking three-dimensional finite element analyses of two raft sizes, and various pile layout patterns, including the rafts with piles distributed evenly and only in the central area of the raft. The computer software PLAXIS 3D with the Mohr-Coulomb constitutive soil model was used to facilitate the modeling of such cases. The results presented in this paper indicate how strategically locating the piles could reduce the differential and total settlements.

By Josef K. Alter

Long-term performance and behavior of post-tensioned ground anchors subjected to axial cyclic loading constitutes an important aspect of the stability, reliability and overall performance of wind turbine deep foundations. Axial cyclic loading of post-tensioned (PT) ground anchors in soils has not been thoroughly investigated as evidenced by the research conducted for this topic. This paper evaluates research test data, available literature, and industry expert opinion on the current status and problems of deep foundation post-tensioned ground anchor (PTGA) technology, as applicable to the wind energy industry. It also introduces a proposed design solution that addresses the problems of construction cost and long-term performance of wind turbine deep foundations in soils subjected to dynamic cyclic axial loading. Deep foundations using ground anchors for wind turbines have only recently gained attention as a possible viable alternative to the mass spread footings currently in use. One of the primary problems with general acceptance of current PTGA designs is the need for long-term anchor maintenance. The research that was conducted for this study indicates that current literature only partially addresses the many factors influencing load capacity and pullout performance of ground anchors. The lack of information indicates the deep foundation industry has fallen behind in designing and implementing new technology to improve safety and performance, ensure sustainability, reduce costs, and address environmental responsibility. This paper describes the significance of this problem as it applies to the wind energy market, and proposes a new technology solution. The research, expert opinion, and analysis presented by the author is used to support the premise that ground anchor construction cost and long-term maintenance can be reduced with PTGA systems using the Con-Tech Systems (CTS) patent-pending Groutable Void Form (GVF) technology.

Jan 1, 2010

By Daniel W. Mageau, Larry W. Applegate, Aaron K. McCain

"An innovative method of ground freezing was successfully tested to create a “dry” excavation condition for a new building foundation at a site in downtown, Miami, Florida. The subsurface conditions in Miami generally consist of very porous, weak limestone and sand with groundwater near the surface. Water flow through these materials can be very high. Dewatering is extremely restricted in Miami so deep below-grade structures are rare and expensive. A new, innovative method to allow deep excavations in dry conditions without dewatering involves the creation of a thick, temporary, frozen soil plug below the planned excavation depth across the entire site to cut off vertical groundwater flow during construction. Frozen soil is impermeable and very strong and has long been used for temporary structural and water-tight shored walls. Using the same proven principals, frozen soil plugs are very effective at cutting off water from the bottom of the excavation as well as resisting upward buoyant forces. This new freezing method can be used for fairly deep excavations in new building construction supported on deep foundations. The building piles act as temporary anchors for the frozen plug to resist very high upward buoyant pressures until the permanent structural slab is completed.IntroductionUnlike other Cities, below grade basements are rare in Miami. The few basement foundations constructed have utilized a cumbersome and expensive method of excavation and shoring involving underwater excavation, tremie slabs, and commercial divers. The key issue for underground construction in this area of the country is the vertical flow of groundwater through the base of the excavation. To deal with this issue in the past, the contractor first installed all of the building piles and the perimeter shoring walls. Then, interior sheet pile walls are installed to create small manageable excavation pits. Each pit is then excavated through standing water “in-the-blind” and around the buildings support piles. The final excavation, interior struts, and inspection is performed by commercial divers. Finally a thick foundation tremie slab is poured under water. This method could be successful but proved to be time consuming and expensive. In addition, some building piles were occasionally damaged during the under-water construction process."

Jan 1, 2015