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By Quanchen Sun, Mohammed Z. E. B. Elsahife, Anthony Fisher, Chris Barker, Jennifer Schooling

A review of the literature shows that pile integrity is a significant concern in pile construction. Recently, a new integrity test, thermal integrity profiling (TIP,) has been put into use in foundation construction. It measures temperature changes and thermal profiles of concrete during curing. Heat generation and dissipation of early-age concrete is determined by the concrete mix, the ground conditions and the shape of concrete structure. The current data interpretation practice is primary based on experience. Anomaly detection through direct analysis of temperature profiles is currently indicative or suggestive and temperature signatures are usually similar, and numerous causes are not easily isolated. The core of the TIP testing technique, i.e. collecting detailed temperature measurements along the pile during the hydration process, is promising but a new interpretation approach is required. In this paper, a new interpretation approach has been developed in which TIP constitutes the first step. An investigative staged process is then followed to establish and assess the anomalies in the problematic regions along the pile employing the combined use of detailed finite element (FE) simulations, the actual temperature data from TIP and genetic evolution algorithms. In each stage, more details could be revealed about the anomalies being investigated including, ultimately, location, size and shape; this staged process enables practitioners to follow a riskbased approach and decide whether or not to pursue subsequent stages depending on the results they get at the end of each stage. This new approach, depending on the stages required for the analysis, will potentially avail practicing engineers of crucial test results about the quality of the pile immediately following pile construction, hence enabling repair and remedial work straight away at a lower cost.

May 1, 2022

By C. Dai, S Raathiv

The Waikato Expressway is one of the New Zealand Transport Agency’s (NZTA) seven roads of National Significance. Coffey is part of the City Edge Alliance engaged by NZTA for the Hamilton Section of the project. The 22km Hamilton Section is the largest and most geotechnically complex section of the Expressway. The Mangaonua gully in Sector 6 is the most challenging geotechnical area of the project for piling works. Together Coffey and Brian Perry Civil have carried out the temporary and permanent design and construction of embankments, piling works, retaining walls and soil improvement works for the bridge construction. The design and construction works were governed by weak alluvial layers and artesian pressure layers several meters beneath the ground level. This paper presents the action taken to improve the foundation of temporary platform, control the artesian pressure, prevent bentonite leakages into the highly permeable alluvial layer and challenges in the base grouting process. This paper summarises the key components in the construction and supervision of bored piling works and outlines innovative solutions for challenges which we faced during the construction.

Nov 1, 2022

By Melissa S. Beauregard, Randall A. Pietersen

This study focuses on quantifying the effects of water infiltration on a full-scale energy pile system’s ability to meet the thermal demand of an HVAC system. Theoretically, an energy pile system should increase its thermal capacity after a rain event due to increased moisture content creating an increase in thermal conductivity of the surrounding soil matrix. The United States Air Force Academy has an energy pile research site consisting of 8 full-scale energy piles located below a shower facility. The local colluvium surrounding the piles allows for relatively high water infiltration during rain events. This study uses an 11kW Precision Geothermal Geocube to apply a thermal load on two single-loop piles. A weather station located south of the structure records atmospheric conditions. Results indicate that moderate rain events can caused up to a 23% increase in the system’s thermal exchange capacity. This change is due to the increase in moisture content near the surface, which penetrates to deeper soil layers with time. The time required for moisture to penetrate to greater depths and then dissipate in the soil matrix, explains why increased system performance is seen for over a week following the passing of a singular rain event. 1 INTRODUCTION With a “future-forward” focus, there is an ever-pressing economic and environmental need to use sustainable sources to meet growing energy needs. HVAC is typically responsible for 34% of the overall energy required by commercial buildings and 48% of the energy required by residential buildings (USEIA, 2009; USEIA, 2012). Energy piles are a low cost, sustainable technology that have been used to offset this energy demand incurred by a building’s space heating and air conditioning requirements. An energy pile consists of heat exchanging elements in a closed loop system integrated into a building foundation and connected to a ground source heat pump (GSHP). It is most common for these heat- exchanging elements to be constructed within a drilled shaft foundation due to both construction practices and geometric considerations. This system operates based on the principle that at a certain depth below ground (typically 4 meters) subterranean temperature remains constant at a value equal to the mean annual air temperature at a given location (Kavanaugh et al., 1997). This allows the soil to function as a heat sink for cooling operations and a heat source for heating operations when exchanged within this zone of relatively constant temperature. For the past 25 years, the implementation of energy pile technology in public, residential, and even large-scale architectural complexes has slowly expanded which has created an increase in research into the topic as a result (Brandl, 2006; Hamada, 2007; Sekine et al., 2007; Gao, 2008; Bourne-Webb, 2009; Stewart and McCartney, 2013; Murphy et al., 2014). When pile construction takes place beneath the groundwater table, soil is under fully saturated conditions, maximizing thermal exchange for a GSHP system. Under unsaturated conditions, however, changing moisture contents change thermal conductivity values in a soil, which affect a GSHP system’s ability to meet a thermal demand. The observational data presented in this paper apply to GSHP systems in unsaturated soil conditions.

Jan 1, 2019

By Christophe H. Locussol

D.C. United, the professional soccer team located in Washington, D.C., completed a 20,000 seat capacity stadium in July 2018 named Audi Field. The project initially considered a foundation system consisting of roughly 800 prestressed concrete driven piles configured in groups with pile caps. A value engineering alternative proposed in a design-build manner ultimately resulted in the use of 300 single element Auger Cast Piles (ACPs) for the foundation system. The ACPs ranged between 1.5 ft and 4 ft in diameter, were up to 85 ft in length, and were connected through a system of grade beams to accommodate large lateral induced loads. Limitations in conventional analytical methods were encountered during the structural design of the piles due to the complexity of the lateral loading and pile fixity conditions. An innovative approach using advanced finite element modeling that incorporated the framing effects of the grade beams was required to meet the strict movement criteria despite large lateral loads.

By Martin D. Larisch, Ronald Damen

The design and construction of temporary working platforms for cranes and piling rigs is a high-risk activity. It requires the careful selection of the appropriate input parameters to obtain the correct load cases, as well as the application of robust and reliable design methods to assess the required thickness and stiffness of the working platform. The document introduces some of the most common and most relevant guidelines for working platform design which are currently used in Australia and New Zealand. The authors will also discuss the basic assumptions and considerations about load transfer from construction plant, debate ground risk, compare the applicability of different design methods for various ground conditions and suggest some common verification methods for working platform certification.

May 1, 2022

By Antonio Zechini, Giuseppe Iorio, Massimo Grisolia

"The new C Line of the Rome Metro runs northwest to southeast across the city center, with 30 new stations and a total length of more than 15.5 mi (25 km). Due to the presence of a dense urban environment, the selected solution for the construction of the stations consists of a cutand- cover excavation, which is retained by multipropped diaphragm walls to minimize settlement and prevent damage to the nearby structures. The bottom of the excavation of the underground stations are about 82 ft to 98 ft (25 m to 30 m) below ground surface, and about 66 ft to 82 ft (20 m to 25 m) below the groundwater table. To ensure dry conditions and to prevent hydraulic base heave instability, deep well systems were designed and used to lower groundwater level and piezometric head during excavation. The dewatering field tests showed how the local stratigraphy strongly affects the dewatering efficiency. Finite element modeling (FEM) of steady state filtration were used to compare the soil permeability with Lefranc in-situ test results and to verify the efficiency of the grouted plugs. The geological sequence along the new C Line consists of a very heterogeneously layered deposit. The base deposit of stiff overconsolidated clay (“APL,” Pliocene age) is overlain by fluvio-palustrine very dense sandy gravels (“SG,” Pleistocene age), which are then overlain by medium stiff clayey silts or dense sandy silts (“AR” or “ST,” Paleotevere units). These deposits are overlain by covered by pyroclastic volcanic soils, tuff, silty sand and sandy silt (Middle to Upper Pleistocene) deriving from the Colli Albani apparatus. A layer of made ground (“R”) of varying thickness covers the stratigraphic sequence and the natural soil profile everywhere.The local hydrogeological framework is very complex and characterized by a double groundwater system. The upper main aquifer is mainly represented by the “pozzolane sequences” (“PR/PN”), while the lower aquifer consists of a deposit of sandy gravel (“SG,” Pleistocene), which is underlain by marine claystone bedrock (“APL,” Pliocene). The pyroclastic deposits (e.g., pozzolane, lithoid and pseudolithoid tuff and clayely tuff) show large variations in permeability due to porosity, compaction processes, sealing and secondary fracturing. Permeability values for each soil type were determined using Lefranc tests at variable head and using pumping tests. The Lefranc tests indicated a wide range of permeability."

Jan 1, 2017

By Russell J. Denny

"A 25m deep cut-off wall is required for environmental remediation of a Former Chlor-Alkali Plant. Extensive trials were conducted to verify the effectiveness of the mixes proposed, with the requirements of the cut-off wall to include limiting criteria for hydraulic permeability, vapour permeability and strength, over a 100 year design life. A limited number of field CSM trial panels were installed on a nearby site with similar stratigraphy, and a variety of mixes and mixing methodologies were used, together with the extraction of deep wet grabbed samples from the panels, which were tested for strength, hydraulic permeability and gas permeability. Test results obtained from these trials revealed a trend which allowed the construction methodology to be decided. Further to this, the mix design needed to be resolved, together with sensitivity analysis on the variations in the mix which might occur during construction, as a result of normal unavoidable variations in construction technique. Laboratory sampling would be used at lesser expense, to resolve the final mix design and analyse the sensitivity of the possible mix variations. An initial series of laboratory mixed samples were prepared using soil samples and groundwater obtained from the site, and testing carried out. However the test results in this initial series of laboratory tests could not match the results which had been achieved in the field trials. Closer scrutiny and investigation and rounds of sampling and testing, then revealed laboratory techniques for mixing and sampling which provided a logical way to match the actual field test results. CSM Construction is due to commence soon and will provide more extensive results which can be compared back to the laboratory trials. This project provides a valuable opportunity to resolve methods of laboratory sampling so that they compare well with results from in-situ deep mixing.INTRODUCTIONThe former chlor-alkali plant at Botany, NSW, which operated from 1945 until 2002, used mercury cell technology and brine solution to manufacture chlorine, caustic soda, hydrochloric acid, sodium hypochlorite and ferric chloride. Mercury contamination is present in the permeable alluvial soil profile beneath the site. The mercury is present in the form of elemental and inorganic mercury, together with dissolved methyl mercury in the groundwater and soil profile beneath the site and also down-gradient of the site, to depths of up to 25m. Residual clay and sandstone bedrock at approximately 25m depth are relatively impermeable and limit the contamination plume. A cap and contain approach has been recommended by consultants Golder Associates, and this involved a subsurface containment wall, or cutoff wall, to restrict groundwater ingress and egress, and lateral subsurface vapour migration. The cut-off wall is situated on the perimeter of the site, with a total length of 430m and passing through alluvial Botany Sands, with a nominal key into the underlying residual clay or sand stone at 20 to 25m depth. An HDPE liner insert was proposed for the upper 7m of wall above the water table, to further limit gas permeability."

Jan 1, 2015

By Donald A. Bruce

"The Deep Mixing Methods (DMM), in their current forms, have been employed in the United States since 1986, although an earlier version had seen service from 1954. The earlier developments were strongly influenced by practices in the Nordic countries and Japan, while by the late 1980’s several DMM systems had been developed in the U.S. itself. Since then, DMM has continued its evolution, principally via the challenges of a series of large, landmark projects, but also via distinct, significant technological advances. This paper highlights the key points in the history of DMM in the U.S., and provides an overview of the different methods currently in use.IN THE BEGINNINGIt is a common misconception that the history of applications of the Deep Mixing Methods (DMM) in the United States dates from 1986 when SMW Seiko Inc. — a subsidiary of Japan’s Seiko Kogyo Company — was established in the Bay Area. However, the author believes that Intrusion Prepakt Co.’s patented MIP (Mixed in Place) system had been used, albeit sporadically (about 30 projects are recorded), since 1954 (FHWA 2000, 2001). Ironically, by 1961 this single auger method had been extensively used under license in Japan for excavation support and groundwater control — by the Seiko Kogyo Company. By 1972, the original MIP technique had been succeeded by more advanced Japanese methods, involving multiple augers. Intrusion Prepakt have long since become defunct.The first systematic studies of contemporary Deep Mixing Methods in Japan began in 1967 when the Port and Harbor Research Institute of the Ministry of Transportation began laboratory testing using granular and powdered lime for treating soft marine soils. Fundamental studies continued through the early 1970’s, by which time the development of industrial scale equipment was well advanced, having its first application on a marine trial near Haneda Airport. Coincidentally, laboratory and field research also began in 1967 in Sweden (“Swedish Lime Column Method”) for treating soft clays using unslaked lime. Reportedly the progenitor was a Norwegian, Kjeld Paus, who had made observations on fluid lime columns in the U.S. It would seem that developments in Japan and the Nordic countries proceeded independently until 1975 when the technology leaders from each group (Broms and Boman; and Okumura and Terashi, respectively) presented their — very similar — findings at a conference in Bangalore, India. Limited technical exchanges ensued thereafter.Whereas the Nordic developments continued to focus on the use of dry reagents (cement and lime) and relatively light equipment compatible with operating on and in very soft clays and organics, the Japanese progressed into the use of fluid reagents (cement-based grouts) and heavier equipment for both marine and land-based projects. Thus, by 1986, there were a large number of proprietary (wet and dry) DMM systems in Japan, and a rapidly growing market already by then accounting for over 12,000,000 m3 of ground treatment."

Jan 1, 2015

By Gerald Verbeek, Erick Baziw

"Downhole Seismic Testing (DST) is an important geotechnical testing technique for site characterization as it provides low strain (<10-5) in-situ interval compression (Vp) and shear (Vs) wave velocity estimates. These velocities are determined by obtaining relative arrival times of source waves as they travel through the stratigraphy and are recorded by one or more vertically offset seismic sensors. A challenging aspect of this process is to characterize the seismic data sets to determine the analysis method that will result in the most accurate interval velocity values. This paper introduces an assessment technique which utilizes linearity estimates (i.e., hodograms fitting straight lines) from the polarization analysis in conjunction with crosscorrelation coefficient calculations of the full waveforms as well as the deviation of the source wave frequency spectrum from a desirable bell-shaped curve. The paper will provide an overview of the technique and include some examples of actual data sets where the technique was applied to analyze those data sets.1. INTRODUCTIONIn general terms, Downhole Seismic Testing (DST) such as Seismic Cone Penetration Testing (SCPT) is a geotechnical technique for measuring in-situ shear and compression wave velocities (VS and VP respectively). The main goal in DST is to obtain arrival times as the source wave travels through the soil profile of interest, and from these arrival times the velocities are then calculated. Figure 1 shows a schematic of the typical DST configuration: a seismic source is used to generate a seismic wave train at the ground surface. One or more downhole seismic receivers are used to record the seismic wave train at predefined depth increments. The downhole receiver(s) may be positioned at selected test depths in a borehole or advanced as part of an instrumentation package as in the case of SCPT. When triggered by the seismic source a data recording system records the response of the downhole receiver(s)."

Jan 1, 2017

By W. L. Chong

For a project located in Docklands Victoria, a high-rise development was proposed where the geology comprised soils of various compositions and consistencies to approximately 50m deep before being underlain by a siltstone bedrock. Due to the structural loads and spatial constraints, the majority of the foundation piles were designed to be socketed into the siltstone. Key factors in selecting the Continuous Flight Auger (CFA) technique as an effective piling solution are explained. These factors included structural and geological considerations, piling rig capabilities, pile testing regime to verify load performance and integrity, the extensive suite of construction quality controls and instrumentation records required while also achieving an appropriate piling budget and program. This paper also described how these factors underpinned the design approach of the final piling scheme. Critical aspects considered during construction and post-construction quality and pile testing records required to meet and satisfy the strict project piling specifications are also presented. The project adopted what may be considered the “best practice” in deep CFA piling. To the author’s knowledge, this project achieved the record for the deepest CFA piles in Australia where multiple piles to 53.8m deep were constructed.

Nov 1, 2022

By Brian E. Ladd

"A load test program was performed on two auger cast piles constructed in the Inner Coastal Plain geology of North Carolina. Both test piles were installed through Coastal Plain deposits and into underlying Piedmont residual soils; one test pile was embedded into partially weathered rock (PWR). The recommended 100-ton design load was confirmed by a test program that included instrumenting the piles with strain gages. The two piles performed differently during the load tests due to the effect of embedment into PWR. Loading Test Pile No. 1, which was not embedded into PWR, to failure at about 230% of the design compressive load allowed for evaluation of the mobilization of the ultimate shaft and end bearing resistances. Mobilization pile resistance was evaluated by comparing shaft and end bearing resistances to top of pile deflection (d) normalized by the pile diameter (D). For Test Pile No. 1, the ultimate average shaft resistance was achieved at d /D of about 7.5% and ultimate end bearing resistance at d /D of about 9.5%. Test Pile No. 2, embedded into PWR, achieved a d /D of only about 4% at 200% of the design load and was not loaded to failure. Shaft resistance was mobilized at a different rate within each individual geologic layer, i.e. ultimate shaft resistance did not occur simultaneously for all geologic layers. As the available total shaft resistance was exceeded and end bearing mobilized, the unit shaft resistances reduced from the peak values. A modified Davisson offset using d /D of about 6.5% appears applicable for evaluating the ultimate capacity of auger cast piles in the Inner Coastal Plain.INTRODUCTIONAuger-cast-in-place (ACIP) piling was developed in the 1940’s and patented in 1956 (Neely, 1991). Since patent expiration in 1973, ACIP piles are abundantly used in the United States, particularly in the southeast. However, most literature addresses driven piles constructed in sand and clay with lesser discussion of drilled piles. Conventional design methodologies (a- method, ß-method, SPT or CPT correlations, etc.) are based on data derived from numerous projects in a great variety of geologies. O’Neil (2001) notes that there are significant levels of uncertainty in the “universal” databases as evidenced by coefficients of variation of 0.35 to 0.40 for geotechnical parameters (su, SPT-Nvalue, etc.) used to estimate pile capacities.There is a need to develop local databases developed from data obtained from load tests that measure shaft resistance and end bearing. This paper presents the results of load tests conducted on axially loaded auger-cast-in-place piles constructed in the Inner Coastal Plain geology of North Carolina. Shaft resistance, end bearing, and movements that initiated mobilization of these resistances are described. The information presented herein can be used to refine geotechnical correlations and parameters applied in auger cast pile design methodologies."

Jan 1, 2017

By Brain E. Ladd

A load test program was performed on two auger cast piles constructed in the Inner Coastal Plain geology of North Carolina. Both test piles were installed through Coastal Plain deposits and into underlying Piedmont residual soils; one test pile was embedded into partially weathered rock (PWR). The recommended 100-ton design load was confirmed by a test program that included instrumenting the piles with strain gages. The two piles performed differently during the load tests due to the effect of embedment into PWR. Loading Test Pile No. 1, which was not embedded into PWR, to failure at about 230% of the design compressive load allowed for evaluation of the mobilization of the ultimate shaft and end bearing resistances. Mobilization pile resistance was evaluated by comparing shaft and end bearing resistances to top of pile deflection (?) normalized by the pile diameter (D). For Test Pile No. 1, the ultimate average shaft resistance was achieved at ?/D of about 7.5% and ultimate end bearing resistance at ?/D of about 9.5%. Test Pile No. 2, embedded into PWR, achieved a ?/D of only about 4% at 200% of the design load and was not loaded to failure. Shaft resistance was mobilized at a different rate within each individual geologic layer, i.e. ultimate shaft resistance did not occur simultaneously for all geologic layers. As the available total shaft resistance was exceeded and end bearing mobilized, the unit shaft resistances reduced from the peak values. A modified Davisson offset using ?/D of about 6.5% appears applicable for evaluating the ultimate capacity of auger cast piles in the Inner Coastal Plain.

By Stephan A. Jefferis, Adrian H. Bath

"This paper draws together some themes on the durability of barrier systems, and particularly cementitious systems. For contaminated land and water retaining structures, durability can be poorly addressed at all stages of a project, from specification, to barrier material selection, barrier design including toe-in and through to performance assessment in operation. Permeability (hydraulic conductivity) is a dynamic property which will vary over time as reaction processes propagate through a barrier. However, laboratory testing, when undertaken, tends to be focused on short term tests with aggressive chemicals so that the effects of longer-term processes such as carbonation and leaching by permeating water are missed. For water retaining structures, carbonation and leaching actually may be the most significant processes affecting barrier performance as the groundwater adjacent to many water bodies can be otherwise rather benign (as regards bentonite and cementitious systems). These and other reaction processes have been modelled in the arena of nuclear waste repositories and procedures are well recognised. However, such procedures have yet to be widely adopted for the assessment of other barrier systems.INTRODUCTIONOver the last few decades there has been an enormous amount of laboratory research on the durability of barrier materials or more specifically papers reporting the results of permeability tests. Unfortunately there is a much smaller literature on scaling test results to barrier dimensions in the field or to required design lives. Although in the geotechnical industry durability research has been largely laboratory based, in the nuclear industry where relevant timescales are multi-millennia rather than decades, research has been heavily underpinned by geochemical modelling. A significant purpose of this paper is to examine the tools that may be used to analyse the results of tests on barrier materials used in geotechnical engineering, for example, for water retaining structures and contaminated land and draw the attention of the construction industry to the potential of the modelling procedures developed for nuclear repository assessments. Modelling can help to identify underlying processes and so augment information from laboratory testing focused on changes of physical properties such as permeability and strength."

Jan 1, 2016

By Andrew J. Ciancia

The construction of the Pennsylvania Station in Manhattan, the Beaux-Arts masterpiece, was completed in 1910. In financial ruin, the Pennsylvania Railroad Company sold the station in the 1960?s and the new Madison Square Garden and the Penn Plaza complex were constructed at the site. The demolition of Pennsylvania Station brought public awareness and outcry to protect historic structures and the Landmarks Preservation Commission (LPC) was subsequently established in 1965. In the 1960?s relatively little engineering data was available on the performance of historic structures during adjacent construction and thus, no published criteria were established by the LPC on allowable movements and vibrations. During the late 1970?s a commercial tower was planned adjacent to the landmark Fraunces Tavern Block (FTB) in lower Manhattan. Through negotiations between the LPC and the developer, Dr. M. I. Esrig and the author were retained to monitor the historic block during foundation construction. The monitoring data and building performance compiled from the project formed the basis of the published 1981 ASCE technical paper by Esrig and Ciancia entitled ?The Avoidance of Damage to Historic Structures Resulting from Adjacent Construction?. Based on the ASCE paper, the NYC Department of Buildings adopted Technical Policy and Procedure Notice #10/88 entitled ?Procedures for the Avoidance of Damage to Historic Structures Resulting from Adjacent Construction When Subject to Controlled Inspection by Section 27-724 and for Any Existing Structure Designated by the Commissioner?, June 1988. This paper describes the author?s recent experience during the installation of deep foundations within, or adjacent to, three Manhattan landmark structures. Discussions are provided on the foundation construction, monitoring programs and performances of the three structures.

Jan 1, 2008

By Mohamed A. Sakr

An experimental study on the behavior of pile group&apos;s arrangement under lateral load was carried out in the level ground and at crest of sand slope 3H: 2V. Tests were conducted on single pile and pile groups with center-to-center pile spacing of 3D. The model piles were founded in sand with relative density 25%. Several configurations of pile groups were used to study the effect of piles arrangement in the group (series or parallel) with respect to slope crest. The behavior of the pile groups in the level ground was compared with the behavior of pile groups at different configurations at the slope crest. Based on the test results, the behavior of laterally loaded pile groups adjacent to a slope crest depends largely on piles arrangement in the group with respect to direction of the lateral load. Pile groups in the level ground have more resistance to lateral loads when they are arranged in a parallel configuration than in a series, whereas the reverse is true in cases of pile groups constructed near to the edge of a slope. It is advisable to use the pile group in series arrangement for groups constructed at slope crest to minimize the effect of the ground slope on lateral capacity of piles and the occurred deflection and maximum bending moment of the lead row in the group.

Jan 1, 2010

By Dave Paul

Dam rehabilitation involves a range of design, construction, and operation risks, some of which are not encountered in new dam construction. These risks can have significant impact on project schedule and project budget. Owners, engineers, and contractors need to understand these risks. Existing dams typically were designed in an era of design and construction standards that have been upgraded and changed. Modern standards will impact the construction approach taken and involve understanding the earlier standards. Knowledge of historical standards/practices as well as current design standards and construction methods is valuable for developing and designing rehabilitation components. Construction records and as-built drawings are valuable when they are available. Rehabilitation projects often consist of older projects where as-built documents or construction records are not available. Where these records exist, many (most) times, they do not fully reflect the current conditions within the dam and appurtenant works. leading experienced practitioners to “expect surprises” both during investigation of the existing facility, as well as during construction. “Surprises” should be expected even when historical records of investigations, design and construction are available. Unknowns, be they known unknowns or unknown unknowns, can be planned for by developing an approach for the design and construction process to identify potential issues/problems, or at least alert the designer and contractor of potential issues. A Risk-Based approach applied for the entire life of the rehabilitation project can be used to alert the parties of potential “surprises” and provide direction for mitigating issues as they arise. This type of approach is particularly effective when the process includes senior practitioners with decades of design and construction experience in all aspects of dams. Minimizing impacts created by “surprises”, particularly during construction, can result in an improved project meeting budget and schedule goals and design standards. This paper identifies and categorizes risk types salient to dam construction, reviews the process of risk identification and analysis, discusses guidelines for risk allocation, reviews strategies to mitigate risks, presents several case studies where risk mitigation strategies were employed successfully (or unsuccessfully), and presents lessons learned. The paper concludes with a summary and recommendations for best practices for Project Risk Management and mitigation that can be used by: Owners; Design Engineers; and Construction Managers, in planning, design, pre-construction and construction phases of dam related projects.

By John E. Lens

Driving bridge foundation piles into glacio-fluvial sands and gravels and glacial tills brought surprisingly longer than predicted driving lengths on several recent projects in Vermont. In some instances, piles drove more than 40 feet past refusal depths predicted from Standard Penetration Resistances from borings terminating in glacial till. Overall, piles developed substantially less skin friction than predicted using common capacity formulas and drove as much as 80 feet longer than predicted in the moderate to dense gravelly and cobbly soils. These piles were driven for one to five span highway bridges within narrow valleys with bedrock ranging from 80 to over 200 feet deep. Piles were for both conventional and integral abutment bridges. H-piles were used for a variety of reasons including lower unit cost, better availability, and better ability to drive through cobbly soils in upper strata. Dynamic testing was used to evaluate capacity, including skin friction and end bearing capacity. In order to develop better pile length and capacity predictions for future projects, VTrans and one of their geotechnical consultants are collaborating to develop criteria for improved pile capacity predictions in these river valleys. We are doing this by evaluating driving and dynamic testing data from four projects in comparison with the Federal Highway Administration (FHWA) DRIVEN pile design software, and methods from Myerhof (1976) and Tomlinson (1981). Our overall objective is to provide a basis for choosing appropriate pile types and reliably estimating pile lengths for projects in this terrain. Bridge foundation design projects in other mountainous terrain share similar design and construction challenges to those encountered in these Vermont projects. These include: difficult exploration drill rig access requiring smaller rigs with limited capability to drill through cobbles and boulders deep enough to reach bedrock; limited experience with displacement piles as alternatives to H-piles in this geology; and relatively greater variability in soil stratigraphy between foundations at these sites as a consequence of the relatively high energy depositional environment in mountainous terrain. This paper presents the case history summaries of the pile driving, results of the ?back analysis? capacity evaluations, examples of solutions employed on these projects to address the lower capacities achieved, and resulting pile capacity design guidelines and prediction criteria for these geologic conditions based on data from these projects.

Jan 1, 2007

By Uwe Hess

For the Danish landworks for the coming fixed link between Denmark and Sweden across the Øresund the focus has been on the environmental aspects of the construction and operation of the facilities. This paper describes how the environmental objectives pertaining to the project have influenced the design and construction of one of the major elements of the Danish landworks, i.e. the tunnel in Sydhavnsgade and under Sydhavn Station. The chosen construction methods for the construction pit bracing and the groundwater lowering will be described along with the observed effects on the environment as shown by simulated or measured values for noise impact, settlements, pumped groundwater and extension of the drawdown cone.

Jan 1, 1996

By Richard E. Sylwester

Evaluating surface and subsurface conditions for marine foundations (bridges, causeways, terminals, etc.) is often done with a limited amount of data. Subsurface information for these projects is primarily acquired using traditional methods, such as boreholes, test pits or divers, which tend to be expensive and limited in the area of coverage. A number of geophysical methods, including precision bathymetry, sidescan sonar, and seismic reflection or subbottom profiling are extremely cost-effective and obtain significantly more data than can be acquired using traditional intrusive methods. These geophysical methods provide detailed surface images and continuous profiles of the subsurface stratigraphy. This information can be invaluable for selecting the best location for geotechnical boreholes and to map potential geohazards such as submarine slides and filled or open scour holes. Offshore investigations conducted for a proposed highway bridge (Knik Arm Bridge, Cook Inlet, AK), the retrofit of two existing bridge (Antioch and Dumbarton Bridges, CA) and a proposed cruise ship terminal (Ketchikan, AK) used a combination of geophysical methods to map water depth, detect and map debris on the seabed, map the thickness of unconsolidated sediment, determine the depth to bedrock and identify potential geohazards such as scour holes. The results of the geophysical investigations will be used to select locations for obtaining geotechnical borings, to extrapolate geologic information between existing or proposed boreholes, evaluate the potential depth of scour and design a pile support pier. Geotechnical engineers, offshore contractors and bridge designers are realizing the importance of the early use of offshore geophysics for (i) site characterization, (ii) to reduce the uncertainty of geotechnical conditions thus avoiding designs that may be overly conservative and thus more expensive and (iii) to assist in selecting locations for geotechnical borings.

Jan 1, 2013

By Dawn Shuttle

In trying to find a grout, or some kind of stabilizer that would work in this application, we established some performance criteria. Of those, what I controlled the most was viscosity, then I had a whole list of other criteria. I needed a long, controllable gel time, durability and the ability to set and stabilize the soil. So I looked through a lot of different stabilizers, some really crazy ones and also the typical chemical grouts that are used. The typical chemical grouts were eliminated because of long-term durability concerns, the need for having extended gel times, and several other concerns. I would be happy to discuss that with you further after the talk if you&apos;re interested. But, generally it was based on viscosity, gel time, and the need for extended gel time. In terms of the relative density of the sand many other grouts could have been used. But the main issue was trying to develop this way to do low pressure grouting that would not cause invasive disruption of the site. We couldn&apos;t go in and grout it, put centers, so most of the other grouts wouldn&apos;t work for various reasons. The forty percent relative density samples were prepared by plubiation. That was both during the cyclic testing stage of the research, which happened a few years back, and also during the box model and the laminar box models at RPI. In terms of what criteria were used to determine the success of the grouting, when I initially started this work what I did was take the grouted samples and I subjected them to cyclic triaxial testing. What I did was take a look at the cyclic deformation resistance of different concentrations of grouted colloidal silica treated sand. I looked first at 20% concentration because I wanted something that I knew worked and then I gradually decreased to 15%, 10%, and 5%. What I was most concerned with was that it did not liquefy and that it was able to hold together it and experience some deformation. But most importantly it needed to not liquefy. So, that was the biggest issue in determining the success of the grouting. In terms of the centrifuge modeling it was done by looking at several components: from looking at the pictures of the bending moments, looking at the acceleration records and how the acceleration records were transferred through the soil, looking at the reduction in the lateral displacement and those kinds of issues. So let me show you the difference.

Feb 10, 2003