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By Sudhir Kumar Das

"The exorbitant price of the land in the metropolis has restricted the horizontal expansion and compelled the owners, the developers and the engineers to opt for vertical expansion. This has resulted in the construction of high rises by extending floors of the existing buildings and developing the new ones for which deep excavation is a must. The multistoried buildings up to a certain height can be founded on shallow depth if the soil beneath can withstand the load. If not, the soil can be stabilized by the latest improvement technology to change the properties of soil to cater the desired load of the superstructures. By such practice the cost and time of completion of the substructures can be reduced in comparison to the substructures needed for deep excavation.The necessity of deep excavation cannot be ignored to create housings, underground parking lots and the other public amenities for the urban migrants in the metropolis.Although most of the metropolis have underground mapping the developers, before starting excavation should be hundred percent sure about the alignment and depth of the utilities so that the excavators do not snap the same to bring cut in water supply, power lines, telephone lines etc, resulting in hue and cry in the neighborhoods of the metropolis due to no availability of the essential services The building/structures coming on the influence zones of the deep excavation should be monitored in all sequences of excavations. In case of building underground corridors for rail or road through open deep excavation under a traffic road the developers, before commencing excavation should shift/divert the dry and wet utilities coming on the way of excavation to suitable locations. The surface traffic need to be diverted either temporarily to an adjacent alternative road or allowed to pass over a decking built over the trench of excavation for the affected length of construction. The soil support system is necessary longitudinally on the two sides covering the width of trench for building corridors. In case of building substructures of flyovers built at different plots along the alignment of the flyover or a multistoried complex built at an isolated plot, the soil support system would be necessary on all the sides covering the plot of construction.The material of construction of soil support depends on the depth, type of soil and the type of permanent structure to be developed. Probable geo-hazards inviting casualties in the deep excavation projects occur due to caving of soil, leakage of wet utilities, seepage through honey comb concrete surfaces, failure of pump used for dewatering etc. A detailed comprehensive planning, management and determination of the project authority is essential for marginalizing the casualties. These prevent unforeseen expenditure in mitigation and help to control the time and the cost over run of overall project. The engineer at site should be more a professional manager than an engineer at site. He should be conversant with the safety and environment rules and regulations applicable to deep underground projects."

Jan 1, 2015

By W. G. K. Fleming

Mr P. Bermingham introduced paper 9.1, describing the development and trials of a new pile load-testing technique that the Authors had termed "Statnamic". The system involved launching a test weight mounted on the head of the pile by igniting chemical fuel in a pressure combustion chamber between the pile head and the test weight. The expansion products from the burning fuel generated large pressures which were used to launch the weight upwards at high velocity. The reaction from this force generates an equal and opposite force at the pile head. This force is typically of much longer duration compared with, for instance, dynamic load testing by drop hammer. In addition the pile experiences a much lower acceleration - typically of less than one g. Because of the long duration blow, the pile is loaded at below its natural frequency and is therefore under a uniform high stress over its full length throughout the duration of the test. The pile behaviour is not dominated by the complex action of an impulsive stress-wave as with standard dynamic testing. The test technique is thus essentially quasi-static. It was anticipated that a ram test weight of 16 tonne would be sufficient to provide the test reaction for a 600 tonne load test. It was pointed out that the device was still at the research stage, but had yielded encouraging results to date. Testing would proceed from model testing and computer simulation to full scale field testing.

Jan 1, 1991

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 James L. Christensen, Gregory Sanchez, Michael P. Walker

The Fogg Museum expansion project required excavation and construction in a congested urban area in Cambridge, Massachusetts. A soldier pile tremie concrete (SPTC) wall provided the support of excavation and now serves as the permanent basement wall of the new expansion of the museum. The existing Fogg museum had a single basement level. The new expansion has a two-level basement for new exhibit space and an amphitheater. The east side of the site is about 20 feet above the basement level of the existing Fogg structure which resulted in a significant unbalanced load that needed to be resolved without damaging the original Fogg structure. The SPTC wall was supported with a combination of tiebacks and internal bracing. The final depth of the excavation was about 40 feet below street level. Strict movement control was imposed because the existing museum contained an Italian Renaissance-style courtyard. The southeast corner of the SPTC wall had to accommodate underpinning of an historic concrete ramp which was ultimately incorporated into the expansion. Challenges during construction included excavating the SPTC wall panels up to 12 feet into argillite bedrock which had occasional diabase dikes and sills. The following topics are discussed in more detail after a general project.

Jan 1, 2015

By Michael Oakland

This paper will discuss the design analysis of sheet pile cofferdams for static and dynamic blast loads. Following construction of the new Willis Avenue Bridge across the East River between Brooklyn and Manhattan, in-river piers No. 9 and No. 10 from the former bridge were demolished, partially by explosive charges. The blast at Pier 10 was conducted first and though the demolition charge was relatively small, it gave confidence that the sheeting could be designed to resist the blast load. This paper primarily summarizes our analysis and performance of a sheet pile cofferdam at Pier 9 used to withstand the larger blast loads, contain the blast debris, and allow excavation of the pier below the existing river bed mudline. The program NLFlex was used to predict stresses and deformations of the cofferdams under dynamic blast loads, using simplified equations to estimate the underwater blast pressures. Specifically, the analysis focused on the stresses in the struts, waler beam, sheet pile interlocks and connection of the sheeting to the waler beam. Design included allowing plastic deformations and limited rupture of the sheet pile interlocks under the blast loading. Comparisons are made between stresses assessed by the dynamic finite element modeling and empirical relationships used within the industry. The performance of the system after the actual blast is discussed as well as details of the performance of welded vs. bolted connections within the system.

By John Mould, Gordon Chen, Michael Oakland, William McElwee

"This paper will discuss the design analysis of sheet pile cofferdams for static and dynamic blast loads. Following construction of the new Willis Avenue Bridge across the East River between Brooklyn and Manhattan, in-river piers No. 9 and No. 10 from the former bridge were demolished, partially by explosive charges. The blast at Pier 10 was conducted first and though the demolition charge was relatively small, it gave confidence that the sheeting could be designed to resist the blast load. This paper primarily summarizes our analysis and performance of a sheet pile cofferdam at Pier 9 used to withstand the larger blast loads, contain the blast debris, and allow excavation of the pier below the existing river bed mudline. The program NLFlex was used to predict stresses and deformations of the cofferdams under dynamic blast loads, using simplified equations to estimate the underwater blast pressures. Specifically, the analysis focused on the stresses in the struts, waler beam, sheet pile interlocks and connection of the sheeting to the waler beam. Design included allowing plastic deformations and limited rupture of the sheet pile interlocks under the blast loading. Comparisons are made between stresses assessed by the dynamic finite element modeling and empirical relationships used within the industry. The performance of the system after the actual blast is discussed as well as details of the performance of welded vs. bolted connections within the system. IntroductionThe Willis Avenue Bridge is one of the major access ways from the Bronx into Manhattan. The location is shown on Figure 1. The original bridge constructed in 1901 was a swing bridge over the East River. The bridge was in disrepair and outdated with regards to its ability to handle the flow of traffic resulting in numerousaccidents.In 2007, Kiewit Constructors Inc./Weeks Marine, Inc., A Joint Venture was selected to construct a replacement bridge. The $612 million project included construction of a new bridge just to the south of the original bridge. The most notable aspect of the construction was floating and lifting the new 350 ft. long swing span in place as a single piece. However, another significant challenge was using blasting to demolish two of the abandoned piers which were within the East River. The blast would be near existing structures in both Manhattan and Brooklyn and would be within 30 ft. of the new bridge."

Jan 1, 2017

By Philip Derbyshire, Dale J. Scheffler

"Continuous Flight Auger (CFA) piling is a variation of Augered Cast-In-Place (ACIP) or augercast piling. In both cases a continuous auger with a hollow stem is used to drill a hole and a pile is formed by injection of cementitious material through the hollow stem as the auger is withdrawn. CFA differs from conventional American ACIP by the use of concrete rather than grout to form the pile, and by the type of equipment used to advance the auger into the ground and withdraw it. CFA installation uses a European style rig (i.e. fixed mast and rotary system) which can produce greater crowd and usually has a larger rotator or drill motor than the standard augercast setup. A standard augercast setup will consist of a lattice-boom crane and a set of leads to house the drill motor and auger. The auger size will range up to 24 inches (610mm). With CFA rigs larger diameter piles can be constructed, 24 to 36 in dia. (610mm to 915mm) are common and the technique has been applied with diameters up to 48-inch (1220mm). CFA makes use of sophisticated computer controlled monitoring systems, which have more recently been introduced for conventional ACIP piling. Developments in CFA have taken place over the last 25 years in Europe and particularly in the UK, but are relatively new in the USA. One application is in the construction of secant (overlapping) piled retaining walls. D.J. Scheffler Inc. recognized the potential of the CFA system following visits to the UK and has introduced its use into California for both secant piling and other applications.BACKGROUNDThe high price of real estate in many of the favored areas of California has increasingly led owners to want to build basements under their houses to increase the floor space available on a lot. Many of these areas are by the coast where the ground conditions are predominately granular and the water table is high. Conventional shoring and dewatering systems have often caused problems with adjoining properties. Clearly tangent walls are not suitable in these conditions because of leakage and loss of ground. The secant pile system, using CFA techniques, has proved very effective at overcoming the problems experienced by other methods. Other applications for CFA secant walls have included use for an emergency job on a highway following erosion caused by unusually heavy rainfall.METHODThe concept of secanting piles, whereby primary(female) piles are installed first and then secondary (male) piles are cut into the primary piles is not new. The method has been known for more than 30 years. Originally ‘Benoto’ grabbing rigs, developed in Japan, were used together with sectionalized double skinned casing and oscillators.This early method was slow, although very effective. More recently high torque rotary machines have been used. Contractors in the UK have increasingly used CFA techniques to further improve productivity of this type of piled wall. The improved capabilities of piling rigs available, as well as developments in concrete technology and instrumentation, have made this possible."

Jan 1, 2005

By Christian Hoyme, Jochen Maurer, Hans Regler

Up to today, it has been very difficult to obtain qualitative and quantitative information about the status and production process of a construction site. It is becoming more and more important to be able to analyze this process so as to notice bottlenecks and interruptions on the site early on. The high costs of each shift in special foundation industry mean that making the wrong decision and/or interruptions can put the financial result at risk. Previously, keeping reliable data meant manual process documentation. This was done either by an additional staff member (incurring high additional costs for training, education, etc.) or by the equipment operators. The latter is critical, because they have to initiate every process step change, leaving no time to log data separately. Studies have shown that there are considerable deviations from the actual process steps. In this paper, a seamless, automated method will be introduced to analyze the construction process. This method recognizes each process step from the equipment data. The main purpose of the data recorded by the piling rig is the need of quality reports and now basis for the presented analysis. Here, a method was successfully transferred from theoretical computer science (compiler construction field) to find application for process recognition. Because the execution of works in special foundation construction can always be defined sequentially and therefore also practiced sequentially, recognition can occur step-by-step. Our method always recognizes the next step, so it does not have to monitor as much data at the same time. Individual trigger points are easier to define. Unlike solutions that are based on a global approach and allocate suitable process steps to data patterns, thereby also creating gaps, the presented method is always seamless. Furthermore, this method can be applied regardless of time or location provided that the necessary machine data is available, which is normally the case with production data logging. This means that construction sites even from the past can also be analyzed and the results used for comparisons. The first results from the analysis of a complete continuous flight augering (CFA piles) installation process of a construction site will be presented.

Sep 8, 2021

By Suzanne R. Hess-Brittelle, Sharon L. Schulz, Tyler J. Quick, Amy F. Ebnet

"Abiquiu Dam is a rolled earth fill dam with impermeable core located on the Rio Chama in New Mexico. Abiquiu has had a history of excessive seepage through the fractured sandstone abutments since water was first impounded in 1963. The foundation was treated with a single row grout curtain in the cutoff trench prior to placement of the embankment. During the 1960’s and 1970’s, the grout curtain was extended 1,000 ft. into both abutments and sections of the foundation beneath the embankment were regrouted. Grouting of the foundation beneath the embankment required drilling through the embankment. Drilling fluid loss or loss of circulation within the impervious core was observed during multiple phases of supplementary grouting and during verification drilling following the 1970’s grouting program. It is likely that the drilling methods employed for these grouting and drilling programs caused hydraulic fracturing of the impervious core. The fluid losses in the embankment may be related to seasonal shutdown layers in the embankment or benches in the abutment foundations. In addition, it is likely that the impervious core was fractured from grout pressures during installation of grout pipe through the embankment.INTRODUCTIONAbiquiu Dam is located on the Rio Chama in New Mexico and consists of a rolled earth fill dam with impermeable core, controlled outlet works, and an uncontrolled rock-cut spillway. The dam was authorized for flood control and sediment retention and was designed as a dry dam, holding flood pools for relatively short durations. The foundation is comprised of Permian and Triassic age, interbedded mudstones and sandstones that were deposited in an active braided stream system. Sandstones are moderately fractured and have variable aperture and infilling. Generally speaking, joints are near vertical. Abiquiu has had a history of excessive seepage through the fractured sandstone abutments since water was first impounded in 1963. The foundation was treated with a single row grout curtain in the cutoff trench prior to placement of the embankment. In 1966-1968, the grout curtain was extended 500-ft into the left abutment and the foundation beneath a 560 ft. section of the embankment was re-grouted. In 1978-1980, the grout curtain was extended 1,000 ft. into the right abutment, an additional 500 ft into the left abutment and the foundation beneath the right 520-ft section of the embankment was re-grouted. The alignments of these grout programs are shown in Figure 1. Grouting of the foundation beneath the embankment required drilling through the embankment. Drilling fluid loss or loss of circulation within the impervious core was observed during both phases of supplementary grouting and during verification drilling following the 1978-80 grouting program. It is likely that the drilling methods employed for these grouting and drilling programs caused hydraulic fracturing of the impervious core. In addition, it is likely that the impervious core was fractured from grout pressures during installation of grout pipe through the embankment. This paper provides a summary of the drilling and grouting methods used during these programs and the potential for damage to the embankment."

Jan 1, 2016

By Oladayo O. Komolafe and Majid Ghayoomi

p-y curves have been used over the years to determine the lateral resistance of piles. This method is popular among practicing engineers due to its simplicity and its ability to determine the slope, displacement, shear force, and bending moment for various depths along the pile. The ultimate lateral load resistance is a key component of p-y curve formulation. The p-y curve formulation by Reese et al. (1974) does not consider the effects of soil’s degree of saturation on theoretical ultimate lateral resistance of the failure wedge. This limits an accurate assessment of the lateral soil resistance near the ground surface and the consequent p-y curves. This paper extends the existing approach for determining the failure wedge in unsaturated cohesionless soils with suction dependency, especially for the depths that are above the water table within the wedge. The modification to the failure wedge analysis was made by considering the variation of the degree of saturation which affects effective stress and lateral earth pressure. Through a set of parametric analyses, the impact of incorporating principles of unsaturated soil mechanics in the estimation of theoretical ultimate lateral resistance is examined, and its implications on lateral pile response are discussed.

Sep 8, 2021

By Douglas Heenan

The fracture orientations were inferred based on theory and previous experience. The fracture pattern was not monitored during the project. Grout volume was recorded at each sleeve port and real time movement monitoring of the building foundation was performed.

Feb 10, 2003

By Nils Schneider, Marc Peters, Stefan Frey, Andrea Fluck

Due to the worldwide population growth, the development of sustainable infrastructure and the exploration of renewable energies plays a key role to handle the rising megacity trends and to limit carbon footprint. Herrenknecht AG is a leading manufacturer of Tunnel Boring machines and has constantly endeavored through its extensive Research and Development programs to address limitations faced by the civil engineering industry as regards to construction equipment capabilities. New mechanized technologies, mainly coming from the tunnelling industry, have been developed by Herrenknecht AG as an efficient alternative to conventional civil engineering, where tailor-made concepts are required to comply with restricted conditions onsite. Very often this innovation led technology capability has meant making construction processes safer due to minimal human intervention and also far more productive due to higher performance as compared to other latest or conventional methods of construction. The rising need for even higher building structures and large-capacity bridges involve the development of innovative deep foundation technologies for on- and offshore operation. Conventional methods like bore piles reach their technical and economic limits under certain conditions. For building shafts and foundations, the mechanized Vertical Shaft Sinking Machine technology (VSM) from Herrenknecht AG is a proven innovation and has now been used in various onshore infrastructure projects worldwide to construct a total of 94 circular shafts in depths of up to 115 meters. It operates below the groundwater level, completely remote-controlled from the surface in a diameter range from 4.5 to 18 meters. Subsequently Herrenknecht noted that Offshore foundations, especially in non-drivable ground conditions such as soft and hard rock (e.g. limestone, sandstone, mudstone, granite etc. or soft soil with high density) and shallow continental shelf (water depth approx. 20-60m), presented construction challenges and equally an opportunity for building high performance equipment. The latter construction conditions usually requires drilled installation methods for applications such as harbor enlargements, bridge foundations and foundations for offshore wind turbines. The Offshore Foundation Drilling technology (OFD®) is Herrenknecht’s latest innovation, incorporating our learnings from the VSM and full-face Tunnel Boring machines, and the OFD® enables a rapid and economical offshore installation in such variable ground and rock conditions. This paper will discuss the technology behind the new mechanized technology of VSM and Herrenknecht’s latest innovation of the OFD® along with their respective application fields in foundations construction. The paper will further present in details, their range of benefits to the construction industry.

Nov 1, 2022

By David Coleman

This paper presents a case history involving the installation of drilled in piles with rock sockets for the Bicycle and Pedestrian Path project located west of the Henry Hudson Parkway within the Riverside Park between 83rd Street and 91st Street at the Hudson River in New York, NY. The paper specifically addresses access and construction procedures for a marine installation when working in an urban and environmentally sensitive setting.

By Mikael Calando, Thomas Joussellin

"San Francisco's rapid growth has caused the city to plan for the Transbay Transit Center Project, a visionary transportation and housing project, that will transform downtown San Francisco and the San Francisco Bay Area’s regional transportation system by creating a “Grand Central Station of the West” in the heart of a new transit-friendly neighborhood that will be home to more than 20 new towers rising a high a 1,070 ft. This paper describes the specificities of using advanced diaphragm wall technology, tooling, equipment and installation practices for deep foundation and permanent underground structures. In particular, this paper will emphasize on the urban constraints, geotechnical conditions, and the novel approaches adopted for the construction challenges of the Transbay Transit Center’s Load Bearing Elements, or Barrette PilesPaperThe Transbay Transit Center Project consists of the construction of a new multimodal, five-story Transit Center located in the South of Market neighborhood near the Financial District in San Francisco. The future Transit Center will incorporate nearly 83,000 square feet of retail, a 5.4-acre rooftop park, an extensive public arts program and bus ramps that will connect the Transit Center to a new off-site bus storage facility and the San Francisco–Oakland Bay Bridge. The new facility will accommodate more than 100,000 passengers each weekday and up to 45 million per year. Additionally, the new Transbay Transit Center will replace the since-demolished San Francisco Transbay Terminal, and nearly 20 towers, such as Salesforce Tower, will take advantage of the height increases allowed through the Transit Center District Plan.The approximately $4.5 billion project features a new five-story structure (including two underground stories) and new bus ramps which include a cable-stay bridge. The deep foundations for the pylon of the bridge (Pylon 9) consist of two each 21 ft x 5 ft barrettes (also called Load Bearing Elements in the US) extending more than 180 feet below grade and 10 feet into the bedrock. The barrettes were chosen because of the combination of high loads, significant depth and small footprint. The barrettes are installed using the Diaphragm Wall technology. Nicholson Construction was contracted by Shimmick Construction to install the cable-stay bridge’s foundation elements."

Jan 1, 2016

By Timothy Flaherty

We observed the boiling in the water very close to the water adjacent to where we were drilling. That only happened at the very beginning before it was switched to water flushing. Yes, it was performed with water flush.

Feb 10, 2003

By Dario Libano, Armando Caputo, Francisco Caputo

"UHE Peixe Angical is a 452 MW hydroelectric power plant located on the Tocantins River in Tocantins, Brazil. In 1999, geologists began feasibility studies to estimate the river’s hydroelectric potential, and the decision was made to proceed with the construction of a power plant. In 2002, after extensive investigation, the studies indicated geological homogeneity at the site for the dam, except for an anomaly detected on the left margin, and construction began on the $1.2 billion project.As the work began, the complex ground conditions presented several serious difficulties. The solution was unlike any undertaken before in Brazil— a 100-m-long secant cutoff wall, with 76 1.8-m-diameter piles of up to 78 m deep. All were placed in a six-month period.In the preparation for the detailed construction plans, further studies in the area of the anomaly better defined the geology so that a treatment program could be developed. The feasibility study had detected silicified rock with high permeability in one area, and an injection curtain was designed with five injection lines. In the other area with an anomaly, further investigation revealed a permeable marble formation that was 50 m thick. Here, a specific injection program with three injection lines was developed.The injections started in February 2005 in the marble formation area. By July of that year, only the primary and secondary holes were drilled from the three lines, resulting in a space between injections of 1.50 m. By the end of July, the drilling was halted. The contractor had identified a thick area of heterogeneous material below the transition zone that was characterized by a mixture of soil, fractured rock and hard fractured rock. The anomalies were detected while drilling, and both the general contractor and the designer concluded that the phenomenon of “piping” was taking place.Constructing a positive cutoff wall became a priority."

Jan 1, 2009

By Michael Cianchetti, Nadir Ansari, Matthew Janes

"PROJECT DESCRIPTIONThe R C Harris Filtration Plant underwent an expansion to install an underground sludge treatment capability consisting of a series of underground tanks within stepped excavations 12m (39 ft) and 10m (33 ft) deep into compact, wet sands over stiff clays and clayey silts.Concerns regarding the original structure influenced designers to set the lateral deflection limit for the proximal front footing at 4mm (1/6 in), (0.03% excavation depth). The design-build team indicated at the time of tender that the movement criteria was unattainable using the tender design. Through extensive Fast Lagrangian Analysis on Continua (FLAC) and a novel construction geometry the design-build team crafted an alternative that produced significant savings over the original concept and met deflection concerns.GEOTECHNIQUEThe hillside site drops 14.5m (47.6 ft) over a distance of 53m (174 ft) between the existing Filter Building on the north and the Services Building on the south. The soils adjacent to the Filter Building consist of 6m (20 ft) of sandy fills, to the footing elevation, over compact sands and layered dense sands and silts to a depth of 10m (33 ft) below existing footing. Beneath the silts lies a 10m (33 ft) thick stiff clayey silt, 2m (6.6 ft) of sandy silt till (containing cobbles and boulders) and an artesian gravelly sand at a total depth of 30m (98.5 ft).The tender information was deemed inadequate to accurately determine soil parameters for a finite element analysis. As a result, the design-build team performed pre-tender Cone Penetrometer Testing (CPT), including dynamic analysis. The CPT data indicated stratigraphy consistent with the conventional bore hole exploration (SPT results) however, the CPT data provided consistently superior soil strengths. The CPT data indicated the sands and silts were dense to very dense throughout their full thickness. The clayey silts below the sands were found to have shear strengths in the 100 to 200 kPa (14.5 to 29 psi) range with an Over-Consolidation Ratio (OCR) ratio of 1.5 to 2. The dynamic analysis, while low strain, indicated very competent behavior with Young’s Modulus values in the 200 to 350 MPa (29,000 psi to 51,000 psi) range. The CPT derived shear moduli and OCR values were vital in determining the soil engineering parameters used for the FLAC analyses."

Jan 1, 2007

By Stephan Fisch, Franz-Werner Gerressen

"The use of cut-off-walls (COW) for the open pit coal mines has been used for decades. They have been used to reduce the negative hydraulic impact to the surrounding area caused by the open pit mining. The pile-guided trench cutting system is a worldwide unique technique, originally developed by the engineers of the mining companies themselves. It guarantees a continuous, joint free, COW during a continuous installation process. At this specific site in Welzow, this technique has been pushed to new limits in order to address the local lake region. Depth capability has been designed to about 430 ft (130m), proven are already depth of about 360 ft (110m) at a constant trench width of 39 inch (1000 mm). This project is approximately. 6.8 miles (11 km) long of COW, scheduled to be completed in 12 years period. About 2.05 miles (3.3km) have been installed, which is equivalent of about 3.5 Million ft² (330,000 m²). The system flushes special clay which forms a filter crust at the inner surface of the trench. Only natural clay resources used, in order to achieve the cut-off effect (colmation effect). The paper explains the installation process of the cut-off-wall as well as the equipment systems developed specifically for this project. After a successful start of the first phase of the project, the next step in the advancement of the equipment is already underway to enable the installation of greater depth to approximately 490 ft (150 m +) and beyond. The next generation equipment system is scheduled to start operation around 2018 INTRODUCTIONThis Serbian saying “Bóh je stworil Lužicu a cert je zaryl brunicu – God created Lusatia and the devil buried brown coal underneath it.” captures local communities’ ambivalence towards lignite.Lusatia is an almost entirely flat stretch of land between the Elbe and Neiße rivers dominated by glacial sands. On the surface, the heathland and woodland is hardly noteworthy. However, three large lignite mining regions, two in Brandenburg and one in Saxony, in the east part of Germany, divert the attention to underground level, down to depths of up to 120 meters. Here, seams crisscross the earth like ribbons. They were formed in the Tertiary around 17 million years ago.The mining of the lignite started almost 200 years ago. To enable open pit mining, a suitable dewatering system was required. At first, wells and drainage system were used. With the increasing demand to go deeper to enable full use of the existing resources with greater mining depth, a decision taken back in the 60th of the last century, the amount of water which had to be pumped increased dramatically. In peak times, approx. 1.57 Billion cubic yards per year (1.2 Billion m³/year) had to be pumped. This led to a lowering of the groundwater level for up to 230 ft (70 m), impacting the regional lake landscape. In order to reduce the influence on the water balance, and bring the water level back to pre1970th, a first development took place to implement the use of specific COW system to depth of about 147 ft (45m)."

Jan 1, 2017

By Brian Koch

Michels installed 242 drilled shafts to support the piers for a new basket-handle, true-arch twin bridge across the Mississippi River from Moline, IL to Bettendorf, IA. The installation of the drilled shafts was completed with the simultaneous use of two Liebherr LB36 and one IMT 300 drill rigs. Utilizing barges, 233 drilled shafts were installed in the river. Michels crews also installed 7-ft to 10-ft permanent steel casing into the bedrock, and drilled to depths of 60 feet for each shaft. Despite working in strong currents, freezing temperatures and on rocking barges, Michels crews placed the shafts within 3 inches of plan position. Since the drilled shafts are the key piece in supporting the bridge structure, Michels provided cross-hole sonic logging to verify the integrity and strength of the concrete within the shafts and to add another level of quality control for the owner/customer. Extensive planning took place each day to ensure that tugboats, the linchpin of the project, were being efficiently utilized to shift the barges and materials daily. On any given day, Michels transported five concrete trucks by barge from shore to shaft sites to pour between 40 and 240 cubic yards of concrete. The Michels environmental team was diligent with preparing, discussing and implementing a water treatment plan that was accepted by all state and federal agencies and adhered to strict environmental regulations. Grain hopper barges were rented to control and treat the water that was used in the drilling operations. Another challenge crews ran into was the discovery of caverns when drilling into some parts of the bedrock. Michels worked with the engineer to develop a plan to construct the drilled shafts that encountered the caverns.

Jan 1, 2019

By Tracy Brettmann

The Highway 146 Bridge Expansion Project across the Clear Creek Channel in Houston, Texas was designed on driven precast concrete piles. However, during construction, the piles along one side of the bridge along the main channel encountered obstructions and couldn’t be installed. These obstructions turned out to be the remnants of a previous bridge foundation at this location, which was unknown to the designers since that bridge had been demolished 40 years ago. Those old foundations were massive 20 ft by 40 ft (6 m by 12 m) pile caps 11 ft (3.3 m) thick supported on precast concrete piles 37 to 55 ft (11 to 17 m) long. The foundation re-design for these locations involved installing a single 78 inch (2 m) diameter drilled shaft up to 125 ft (38 m) long to replace the originally planned driven pile supported pile cap. The drilled shafts would need to be installed within very tight tolerances since they were supporting a single bridge column directly above it. In addition to drilling through the obstructions, this work would need to be completed from barges in 30 ft (9 m) of water capable of dealing with both the current and tides affecting this area. The shafts were installed using a multi-step process. The first step involved coring a larger diameter 100 inch (2.5 m) hole through the reinforced concrete pile cap and removing the concrete inside. This was followed by the installation of a 72 ft (22 m) long permanent casing to and removing the soil and existing precast piles inside. Finally, the drilled shaft excavations were advanced to the completion depths (uncased) using bentonite slurry as the support fluid.

May 1, 2022