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By Raffaella Granata, Wesley Schmutzler, Matteo Bertoni

"The Lower Wood River Levee system, at the confluence of the Wood River Creek and the Mississippi River, in East Alton, Illinois, has been plagued with underground seepage and, in 2010, remediation was deemed necessary by the Southwestern Illinois Flood Prevention District Council and the United States Army Corp of Engineers (USACE). The experts enlisted by the council produced a design that provided for constructing a cutoff wall approximately 2,000 feet long and up to 140 feet deep, through alluvial and outwash soils, and embedded in bedrock. This paper will describe the challenges faced by the Quality Control (QC) and Quality Assurance (QA) teams due to the complex nature of the project in conjunction with an extremely thorough QC/QA program.INTRODUCTIONThe “American Bottom” is an area of 453 km2 (175 square miles) in Southwestern Illinois, extending from Alton south to the Kaskaskia River, which is home to 156,000 people. In the 1940s and 1950s the U.S. Army Corp of Engineers (USACE) designed and built a 120 kilometer (74 mile) long levee system to protect the area from a 500-year flood event on the Mississippi River, which flows through it. The levee system has been plagued by under-seepage for several years. The phenomenon has worsened to varying degrees, depending on location, to the point that remediation was needed.The Southwestern Illinois Flood Prevention District Council (SIFPDC), to obtain Federal Emergency Management accreditation, in June 2010 commissioned a team lead by Amec Foster Wheeler for the design and management of the required levee improvements. The team presented in 2011 the project’s first set of drawings showing proposed design features throughout the levee system. The project was subdivided in four areas, based on the controlling levee districts, one of which, the Wood River Drainage and Levee District, was split into three subdivisions: Upper Wood River, East-West Forks of Wood River, and Lower Wood River.The project included the installation of a cutoff wall at the confluence of the Wood River and the Mississippi River in East Alton, IL (Fig. 1). The Engineer of Record (Amec Foster Wheeler) considered the cutoff wall as the only viable solution to stop the severe under-seepage that was undermining the integrity of the Lower Wood River Levee. The Lower Cutoff Wall (LCW) project is the subject of this paper."

Jan 1, 2017

By George Mylonakis

The curvatures and subsequent bending imposed to piles by the surrounding soil during the passage of strong seismic waves is studied. This type of bending develops even in the absence of a superstructure and is referred to as "kinematic bending", to distinguish it from bending imposed to piles by loads generated from the inertia of the superstructure ("inertial bending"). Although kinematic loading may be severe in the presence of sharp stiffness discontinuities in the profile and may lead to damage, it has received little attention by engineers. The scope of the paper is twofold: (i) to discuss some fundamental aspects of seismic pile bending, and (ii) to review some existing design methods. To this end, a dimensionless bending strain parameter (instead of the more commonly used bending moment), and a strain transmissibility function relating pile bending strain and corresponding soil shear strain are introduced. Numerical examples are also presented.

Jan 1, 2002

By Timothy C. Siegel

In response to a solicitation for ground improvement for the construction of a new hospital in Owensboro, Kentucky, the team of Berkel & Company Contractors and Dan Brown and Associates PC designed and installed lightly reinforced cast-in-place piles (known commercially as Cast-in place Ground improvement Elements or CGEs) as part of a composite ground system. The concept of the design is that the structure load is shared between the piles and the soil subgrade. The load sharing is controlled (to some degree) by the placement of a cushion between the pile head and the bottom of the overlying spread foundation. In an effort to confirm the design principles and to better understand the behavior of composite ground, the design-build team performed plate load tests on ground with a single CGE and with a group of CGEs. The small plate test (on ground with a single CGE) characterized the stiffness of the cushion. The large plate tests showed that the cushion will distribute the applied load to the CGEs and to the soil subgrade between the CGEs. On the basis of the plate tests, it was concluded that the plate stiffness can influence the test results. The use of a concrete layer was effective at supplementing the plate stiffness. The cushion was shown to be an important component of a composite ground system by allowing mobilization of the soil subgrade resistance and avoiding a stress concentration at the tops of the CGEs that would otherwise be present if the spread foundation and piles were rigidly connected. Because the composite ground system engages the resistance of the soil subgrade, the structural demand is reduced and consequently there is a potential for savings when compared to a conventional pile foundation. Several foundations for the new Owensboro hospital are being monitored for vertical movement during construction of the superstructure that will extend through 2011. At the time of this paper (mid 2011) the settlement of the foundations due to only part of the structural load (primarily the structural steel) has been negligible.

Jan 1, 2011

By Venda Oliveira P. J., Correia A. A. S., Danisi C. M.

"AbstractA laboratory study has been undertaken to establish common understanding of the creep phenomenon of a Portuguese soft soil chemically stabilised with binders. In order to study the effect of different stress levels on the strength and on the creep behavior of the stabilised soil, oedometer creep tests and unconfined compressive tests were performed at different curing times. Results show that the creep stress level does not influence the unconfined compressive strength. In addition, the creep phenomenon increases the unconfined compressive strength of the treated soil. Two different secondary compression indexes were recognized from the one-dimensional compression curve which increase with an exponential trend with the creep stress level.IntroductionConstruction on soft soils requires a mandatory soil stabilization work to improve mechanical characteristics of the natural soil. Deep mixing method is a worldwide employed ground improvement method, nevertheless the creep phenomenon hasn’t been yet thoroughly analyzed. Most of the published papers have focused on the analysis of the compressibility and the strength of the soil-binder mixtures without considering the creep phenomenon. However, numerical results (Venda Oliveira et al. 2009) have shown that although settlements that occur during the creep stage (namely creep strains) are less in case of treated columns, they are still important especially due to the high loads applied to the stabilised soil. The few published studies about creep behavior of soil-binder mixtures reveal that the stabilization of an organic soil with cement induces a reduction of creep deformations, which is related to the amount of cement used and that the increase of the organic matter of the soil has a negative impact on soil stabilization, further inducing a slight increase in the creep deformations (Venda Oliveira et al. 2012).As part of the current research the effect of different stress levels on the creep behavior of a soft clayey-silt soil was studied. The binder mixture used to enhance the properties of the soil had a specific composition and quantity. Unconfined compressive strength tests (UCS) and UCS creep tests were carried out at pre-set curing times in order to analyze the creep behavior of the soil-binder mixture. In particular five different creep stress levels were studied to understand its influence on the strength and on the compressibility of the stabilised soil. In addition, considerations about the secondary consolidation index are also presented."

Jan 1, 2014

By Muhannad T. Suleiman

Temperatures below freezing significantly enhance the soil shear strength and stiffness and to a lesser extent increase the compressive strength of concrete as well as the yield and ultimate strength of reinforcing steel. Consequently, the lateral load resistance of bridge columns supported by drilled shafts becomes dependent on seasonal weather conditions. To investigate the effects of seasonal freezing on the behavior of bridge columns supported by drilled shafts, large-scale field lateral load tests were conducted at 23°C (73.4°F) and -10°C (14°F) on two identical units at an field test site, which consisted of glacial till soil classified as low plastic clay. The bridge column-drilled shaft systems were subjected to cyclic lateral load with the maximum lateral column top displacements reaching approximately ±30 cm (±11.8 in.). The soil at the test site was characterized at different temperatures using unconfined compression tests in the laboratory as well as in-situ Cone Penetration and Pressuremeter Tests. Using these test results, the lateral load behavior of the column-drilled shaft systems were analyzed utilizing numerical models that consisted of beam elements representing the concrete column and the shaft and lateral springs representing nonlinear p-y response of soil. This paper focuses on comparing the calculated responses of test units with different p-y curves that were developed for the soil near the ground surface using the laboratory and in-situ tests. From the experimental study, the response of the unit tested at -10°C (14°F) was found to show 44% increase in lateral force resistance and 0.84 m (2.76 ft) upward shift of the maximum moment location compared to the response of the identical unit tested at 23°C (73.4°F). Theoretical behavior that included the temperature effects on soil, concrete and steel properties provided good correlation with the measured responses when the soil near the ground surface was modeled using the unconfined compression test or the Cone Penetration Test data, but not the Pressuremeter test data.

Jan 1, 2006

By Luca de Sanctis

The analysis of piled raft foundations in layered soils may be performed by 3D finite elements or by approximate procedures. Among the latter, the code NAPRA (Russo, 1998) is based on the method of the interaction factors and accounts for soil layering by the so called Steinbrenner approximation. A comparison between the results of 3D FEM and NAPRA for some reference layered soil profiles shows that the approximation is fully acceptable for engineering purposes, provided the stiffness of the single pile is properly selected. The interest of the conclusion lies in the fact that the amount of work needed to model a practical problem by NAPRA is but a fraction of that needed by FEM modelling.

Jan 1, 2002

By D. V. Karandikar

Contiguous bored piles have been used in the past for retaining the sides of deep excavation. An innovative version of this method was adopted successfully in two prestigeous projects in Bombay in which in a very constricted and congested locality, adjoining seashore at Walkeshwar, 14 m deep excavations with vertical sides were required. 600 mm dia bored cast-in-situ piles were first installed at 1.2 m c/c and subsequently as the excavation proceeded, they were tied to cast-in-situ RCC waling beams. The shear connectors to the beams were pre-fixed to the pile reinforcing cage at specified depths. The pile / waling beam system was anchored into the ground by installing inclined prestressed cable anchors at the designed depths. The waling beams were also used to support the brickwalls, which formed the required backup wall for fixing the tiled water proofing system. Catch-drains were installed behind the brickwalls for relieving the ground water pressure and thus ensuring a very economic design. The adequacy of the system was proven in that where the system was not installed in time, failure of the sides occurred during monsoon. Whereas in the areas where the above retaining system was installed, there were no problems inspite of heavy monsoon and surcharge of construction materials and equipment. The system became a very effective and economic alternative to an anchored diaphragm wall. The paper presents the case studies of these two projects.

Jan 1, 1996

By Rudolph P. Frizzi

"Abstract Pile design for building structures in the United States is typically performed by: 1) investigating and assigning engineering parameters to the respective ground bearing materials, 2) calculating ultimate pile to ground (geotechnical) capacity which is then reduced by a Safety Factor deemed appropriate by a registered Design Professional thereby arriving at an allowable pile geotechnical pile capacity, and 3) determining the required pile structural section using allowable pile section material properties. It is advantageous to use a Working Stress Design Method (WSDM) approach as one system of loads (service loads) are used in both the geotechnical and structural evaluation. There are a variety of methods used to determine the ultimate and allowable geotechnical capacity, and Building Codes often require a registered Design Professional to determine the appropriate method(s) and capacities. The International Building Code is the Code typically referenced in building design and construction in the United States. Structural design usually follows Building Code requirements and Allowable Stress Design (ASD) procedures. As design of the overlying structure typically follows a Strength Design Method (SDM) approach using factored loads, in some cases piling is first designed for pile-to-soil interaction using service loads, followed by evaluating the pile geometry for factored loads. Construction is the finalization and implementation of the designed piling. As such, project-specific technical specifications are typically developed by a registered Design Professional such that a project Owner can bid, buy, and instruct a Contractor as to the desired piling work and acceptance criteria. There are several Industry groups, including DFI, PDCA, ADSC, and ACI that provide guidance documents which the registered Design Professional can refer to in developing the piling technical specifications. It is the author’s opinion that the registered Design Professional is best suited to observe and verify the piling installation; many Building Departments require verification and documentation by a registered Professional as a condition of final acceptance.INTRODUCTIONPile design for building structures consists of: investigation, design, specification, and verification. In major metropolitan areas within the United States, Building Codes typically identify minimum requirements for each of the above steps. The International Building Code (ICC, 2012) is the Code typically referenced in building design and construction in the United States. Recognizing the ground conditions as well as piling construction means and methods can vary on a site-by-site basis, latitude is given to the registered Design Professional and Contractor to optimize the piling system for the respective project conditions. Field testing and quality control / assurance measures are typically implemented to verify the design intent is attained for the production pile elements."

Jan 1, 2014

By M. B. Wechsler

An analysis is developed for determining the maximum loading, as well as the potential uplift of the piles on bridge pier foundations. There are considered piers supported on two through seven rows of piles, and related to two simply supported collinear superstructures of any structural material. The study leads to different types of influence lines for various load combinations. For load combinations containing vertical loads only, the related influence lines are similar to those as for the bending moments of a virtual span covering the two actual spans, as well as the gap between the two superstructures; and, in this case, the heavier loads should be positioned in the vicinity of the pier. While, in the case when vertical loads are acting together with hori­zontal forces, the related influence lines will indicate where the heavier live loads should be positioned. And they will also indicate on which portions of the spans the live load should be avoided.

Jan 1, 1989

By Klaus Pöllath

The Netherlands RandstadRail project makes use of a large range of sophisticated geotechnical techniques to allow a shield driven tunnel to approach the central station of Rotterdam. This paper describes the construction of three deep excavation pits constructed with 1.2 m and 1.5 m thick diaphragm walls. Besides the presentation of the actual diaphragm wall activities special consideration is given to the break-in and break-out situations of the TBM into the deep excavations pits using sealing blocks and partly glass fibre reinforcement in the diaphragm walls.

Jan 1, 2006

By Nuno Cruz

"The concrete overbreak estimation for bored piles provides the quantification of the shaft’s expansion beyond its theoretical volume. There are stability analysis methods that can be employed before and after concrete pour but as for the moment of decision, during pile cast, the most common method still consists in measuring the rising of the concrete level in order to compare its poured volume with the theoretical pile section volume. This is a determinant parameter to monitor, not only because it assesses the bored shaft stability but also because it represents a direct cost. When analyzing the estimation methods commonly applied on-site it becomes evident that these are often affected by human errors that lead to misleading results. The objective of this paper is to identify those errors and discuss a subject which is usually overlooked. As a general conclusion, it was ascertained that most errors derive from inaccurate volumetric data, working procedures and gauging equipment. By acknowledging these widespread practices deep foundations contractors will be in a better position to make informed decisions on how to correct and improve bored pile stability.GENERALBackgroundWhen executing bored piles, the estimation of its concrete overbreak allows a swift appraisal of the excavation stability during the drilling process. This is simply obtained from the proportion of the poured volume of concrete over the drilled shaft theoretical volume, as shown in equation [1].Where CO = concrete overbreak percentage, Vc = volume of poured concrete, Vr = pile’s theoretical volume. This calculation not only provides a general idea of the shaft’s expansion from its theoretical volume, but also the outline of the excavated column’s geometry. For the latter, the outline will be as accurate as the number of measurements taken for each partial known volume of poured concrete. This means that for each load placed inside the excavation there is a corresponding rising of the concrete level. The profile of the definite pile is then plotted (see Fig. 1) and allows inferring about how stable remained the shaft walls up to the moment of casting.The technological developments in this area have provided other methods for determining pile stability before and after pile cast, such as ultrasonic echo sensing, cross-hole sonic logging or thermal integrity profiling systems. Notwithstanding, concrete overbreak assessment remains as common practice and confers the advantage of providing stability information during the process of pile casting."

Jan 1, 2017

By A. Garassino

A pile design was performed for a thermal power station in Egypt and more than 4000 piles were to be driven. Technical economical reasons suggested the choice of driven composite LACOR piles designed for very high specific loads. Some uncertainties on the behaviour of the pile soil system suggested to perform a test on an instrumented pile. Scope of the test was to verify the possibility of developping the required bearing capacity within the range of the allowable pile settlements values and the effect of the pile joint enlargement on that portion of skin friction to be developped by the upper pile section.

Jan 1, 1991

By Ali Porbaha

The use of soil nailing technology as a cost effective alternative for excavation support and slope stabilization has substantially increased in the United States during the last decade. For example, in the past thirteen years, more than 185,800 square meters of soil nail walls have been constructed in California alone. The conventional soil nail systems pose difficulties when ground conditions are subject to caving, for instance for silty sand (sugar sand) or cobbles and boulders. The construction industry has developed self drilling hollow bar systems (or pressure injected bored, IBO) that combine both drilling, placing and grouting in a single operation as a solution to speed up construction. While the system is extensively used for temporary applications, nevertheless, some concerns, particularly about corrosion, has limited the use of this technology as a permanent system in North America. This study presents several issues related to self drilling soil nail systems, the results of a field investigation and a summary of the research project.

Jan 1, 2006

By Fabian Kirsch

Cyclic behaviour of axially loaded piles has been an issue since studies revealed that the capability to transfer skin friction into the ground is highly depending on the level and the number of load cycles the pile is subjected. It has been shown that degradation of skin friction due to axial cyclic loading leads to accumulating displacements and a severe reduction in pile capacity. In Germany the DIN 1054 as well as the Recommendations of the Working Group 2.1 ?Piles? of the German Geotechnical Society (EA-Pfähle) require the consideration of cyclic loading for the assessment of both the displacements and the capacity. Up to now no broadly accepted design method exists, which enables the engineer to give a reliable judgement on the pile capacity under axial cyclic loading and the displacements respectively. Instead numerous design charts make it possible to distinguish between stable and instable loading levels in order to ensure a design on the safe side. A newly developed design approach based on engineering models is presented which delivers a calculation algorithm for the remaining axial pile capacity after a defined number of load cycles to allow for the analysis of stability of the foundation. Furthermore the computation of accumulating displacements is made possible. The results are verified with pile load tests undertaken at Dunkirk, France and showed that the axial capacity after cyclic loading calculated with the newly developed design approach predicts actual capacity with an accuracy of ±20%.

Jan 1, 2011

By António A. Henriques, António Gomes Correia, Ana Teixeira

"Abstract Pile foundations are often used for important structures, and thus, reliability evaluation is an important aspect of the design. Reliability methods have become increasingly important as decision support tools in different areas. The main benefit of reliability analysis is that it provides quantitative information about the parameters (uncertainties) that most significantly influence the behaviour under study. In particular, the design of pile foundations still involves many limitations and uncertainties, particularly when there is not enough investment in soil characterisation and/or pile load tests. In addition to the uncertainties associated with soil characterisation, physical, statistical, spatial and human uncertainties exist. In this subject, the primary purpose of this paper is to demonstrate the application of reliability methods to geotechnical pile design (axial load). It also presents a simple and practical approach to performing it using Monte Carlo Simulations, intending to provide knowledge for code harmonisation and encouraging the development of such methodologies in geotechnical practice. Sensitivity analyses are shown to understand the influence of each uncertainty type coming from different sources. An application example indicates, corroborating other studies, that the model error is the most influent uncertainty. As such, when using the different models (SPT-, CPT- and PMT-based) for bearing capacity, the results emphasise the need for a well-defined and wellcharacterised resistance model, also these results allow the engineer to understand how important the load tests can be to achieve reliable results and economic designs.1 IntroductionUnlike the approach to reliability evaluation used in structural engineering, the traditional procedure used in geotechnical designs addresses uncertainties through high global or partial safety factors (SF), mostly based on past experience. However, this approach to addressing uncertainties does not provide a rational basis for understanding their influence on design.Furthermore, the new regulation codes and social concerns, such as the sustainability or the economy, are imposing geotechnical engineers to increase their ability to deal with uncertainty in a direct and more rational way. Designs should be economic, sustainable and reliable at the same time. Concerning the reliability part of design, different approaches can be done, but the most important thing to keep in mind is the simplicity and efficiency of the tools and applied methods."

Jan 1, 2014

By Wolfgang G. Brunner

The closing of the gap in the European waterway- net is one of the big and challenging traffic projects following the German reunification. The water canals in the North German plain connect the Rhine river, the border between Germany and France, with the Oder, the German border river to Poland. As early as in the 30's of the 19th century the planning and construction of a ship- lift and a canal bridge started, in order to close this last big gap in the system between the Mittelland Canal and the Elbe- Havel Canal near Magdeburg. This main waterway connects the West of Germany, known for its coal mines and steel mills, with the capital Berlin, and from there it goes on into Poland. The building activities started in 1934 but came to a complete stop in 1942 because of the war. The communist government in East Germany was not interested in continuing this huge project, including the ship lock Rothensee, the canal bridge crossing the river Elbe, the former border river between West and East Germany, and the lock Hohenwarthe due to lack of political backing along with low construction capacity. Now this important project is in progress and this report describes the special foundation techniques used on the great ship lock Hohenwarthe. Hohenwarthe is a double- bay ship lock of considerable scale, which is notable for recirculating water rather than letting it flow. It includes 44 800 m2 ( 481 720 sq. ft) of up to 55 m ( 180 ft) deep cut- off walls, ground water control, 1248 bored piles with a depth of 22 m ( 72 ft ) serving as foundation and 28 000 m ( 91 864 ft) of soil densification with vibroflotation equipment for ground improvement. In the year 2003 the project shall be completed and all ships can travel from the West to the East through Germany without expensive and time- consuming detours through other canals and locks.

Jan 1, 2000

By Carlos Lam, Joram M. Amir, Erez I. Amir

"Abstract The modulus of elasticity of pile material (E) is an important parameter for the interpretation of both static and dynamic loading tests on piles. This value is commonly assumed to be constant with depth though it may not be true for deep bored piles due to the chosen casting method and/or selfweight consolidation. To provide evidence to support this proposition, the results of compressive strength tests on core samples taken from four different studies have been presented. The results show a marked increase in the strength and stiffness values with depth. The results of crosshole ultrasonic tests conducted at another site also confirm the same pattern. It is therefore recommended that before load testing a pile the distribution of the E values along the pile axis should be investigated. This will ensure the use of a realistic elastic modulus value and hence the correct interpretation of thedistribution between the shaft and end resistances.IntroductionThe modulus of elasticity of pile material (E) is an important parameter for the interpretation of both static and dynamic load tests on piles. Multiplying E by the strain measured by either strain gauges (e.g. ASTM D4945) or tell-tales (e.g. Geffen and Amir, 1971) gives the stresses acting at a given pile section. Typically, in the absence of better information, the value of E is derived from laboratory tests on concrete cubes or cylinder specimens taken on site and is assumed to be constant along the pile. While this may be correct for pre-fabricated concrete piles that are cast in horizontal molds, it may not be true for cast-in-place piles that are produced in the vertical position.There are at least two factors that may contribute to the change in concrete properties with depth in a bored pile. First, the casting methods may be by free fall in dry holes (e.g. Kiefer and Baker, 1994) or by using a tremie tube if support fluids are used. In the former case, the earlier batches reach the bottom of the pile bore at a higher velocity and are thus compacted under higher energy. Second, regardless of the casting method, the fresh concrete in the pile bore will always consolidate at least partially under its own self weight. The materials in the lower parts of the pile will therefore experience a higher consolidating pressure. This can reduce the pore volume and the water content in the wet concrete, thus changing the properties of the hardened concrete. Recent research by Justs et al. (2011) has shown that even a relatively small pressure can have a significant positive effect on concrete properties such as compressive strength and stiffness. However, the possible change of concrete properties with depth is commonly ignored by foundation engineers in the current design practice."

Jan 1, 2014

By Brock Wallis, Steve Davidow

The following text will present the concept of rock socketed drilled shafts used to support electrical substation structures, and discuss the cost and schedule risks that traditional design responses to unforeseen shallow rock can pose to a project. Design considerations will be detailed, including rock characterization, shear strength of drilled shafts, and modeling lateral resistance of the shaft and surrounding rock. The specific case of drilled shafts installed for heavily loaded structures at the Moxie Freedom Substation will provide an example of how close collaboration between the engineer and contractor to refine designs based on site-specific feedback can provide tangible benefits to the project. In this example, value engineered designs resulted in an approximate 40% reduction in shaft/concrete volume and a 60% reduction in total rock socket depth. PROJECT OVERVIEW The Moxie Freedom Project included the construction of a new 500 kV switchyard in Berwick, Pennsylvania. The foundation contractor was selected to install both small and large diameter drilled shaft foundations to support the structures within the switchyard. The small diameter shafts were utilized to support transformers, switches, bus supports and a static mast, while the large diameter shafts were used to support one 180-foot monopole and six H-Frame structures. CHALLENGES: ROCK SOCKETED DRILLED SHAFTS Available geotechnical data at the time of bid included limited borings and seismic refraction. The borings were not located at every structure, and the contractor and design engineer were left to interpret desktop studies and geophysics to determine the probable site-specific conditions at each foundation. The data suggested substantial variability in the quality and depth to bedrock across the project area, indicating significant risk of deep embedment into bedrock at all seven large diameter shaft locations. Rock socketed drilled shafts pose unique challenges for both designers and contractors, and the topic has become a focus of national foundation organizations. Traditional design models result in deeper and/or larger diameter shafts where rock is encountered. In the case where site-specific geotechnical conditions are not clearly understood and rock is encountered at shallow depths, this can lead to significant additional rock drilling, impacting overall project cost and schedule. Rock drilling can result in more than ten times the cost of soil drilling and can easily take in excess of ten times longer to excavate.

Jan 1, 2018

By Gustavo E. Armijo

This job was done in Morristown, NJ, with mono fluid system jet grouting for the construction of a new bank building. After the demolition of the existing two story structures, an excavation in loose sandy fill materials was necessary in order to reach the new structure basement level. Due to this jet grouting was selected as a medium to provide both excavation support and permanent underpinning, minimizing the adjacent building settlements. These two adjacent buildings were partially underpinned with a "gravity wall" made with 2 and 3 rows of secant vertical and inclined jet grout columns. Besides the classical jet grouting control methods, during the jet grouting execution, all the drilling and grouting parameters were recorded by a proprietary system called "Slogger". Additionally, after the jet grouting execution, an innovative result control technique was used by means of the application of the same parameter recording system. Some of the production columns were re-drilled and a comparison was made between the obtained drilling parameters and those obtained for the same age test columns. Under the referred existing conditions and in comparison with the conventional underpinning techniques, this project demonstrated that jet grouting, with proper execution and result control, can be faster than them and can maintain the building structural stability and act, at the same time, as a retention system minimizing the existing building settlements.

Jan 1, 2002

By Giovanni A. Bonita

The United States Capitol Visitor Center (USCVC) is one of the largest underground structures ever constructed in the Washington, DC, metropolitan area. The 600,000 ft2 (55,750 m2) structure is entirely underground and immediately adjacent to the shallow foundations of the existing U.S. Capitol building. Interior building columns for the USCVC were supported on 186 drilled shafts that varied in diameter from 4 to 9 ft (1.2 to 2.9 m) and in length from 15 to 45 ft (4.6 to 13.7 m). The vast majority of the building utilities were located beneath the basement floor slab. It was decided at the onset of the project to proceed with construction prior to completion of the design drawings, and coordination between the underslab utilities and the drilled shafts had not yet been finalized at the onset of drilled shaft installation. Given depth and location restrictions of the outlets, relocation of the bulk of the utilities was not possible. Almost half of the drilled shafts were affected, leaving redesign as the most feasible remedial solution. The redesign involved adjustments to the shaft length, diameter, and bell. It took place on a case-by-case basis, sometimes only minutes before installation began. Coordination between the field and design team was excellent, and delay associated with the redesign efforts was minimal. In addition, the detailed, high-quality field records kept by both the contractor and field engineers allowed for accurate and fair estimations of the added drilled footage and concrete volumes placed. The additional service fee, which was minimal, was settled quick and fair.

Jan 1, 2006