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By Takeo Asanuma, Sachihiko Tokunaga, Hirofumi Taguchi, Yasuhiro Ootsuka, Yosuke Tanaka

The Cement Deep Mixing Method (CDM Method) is a ground improving method that has been used for mainly offshore sites to strengthen the soft ground below the sea bottom by injecting and adequately mixing cement slurry with soft soil into the ground to form a ground-improving column. In recent years, the CDM Method has increasingly been adopted for ground- improving work as part of liquefaction countermeasures and earthquake-resistant reinforcement in the shallow waters of river mouths and inland waters. In consequence of that, a pontoon-mounted CDM Method (CDM- FLOAT Method) has been developed for shallow waters, which is equipped with a land-type mixing machine combined with system management equipment and a tide level-based control function. This CDM-FLOAT Method can be deployed at work sites where the conventional offshore-use CDM barge cannot be employed. This report describes the CDM-FLOAT Method and the scope of applications together with construction work procedures, and a representative case of use of the CDM-FLOAT Method is introduced as an example of earthquake-resistant reinforcement of the existing embankment of a canal.

Jan 1, 2015

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used to drill a hole and a pile is formed by injection of cementitious material through the hollow stem as the auger is withdrawn.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 John R. Grillo, Gordian Ulrich, Franz-Werner Gerressen

Most geotechnical construction professionals are aware of piling using hydraulic drill rigs and the so-called Kelly drill mode. Kelly drilling has many advantages as it can work with a wide range of tools facing almost all types of soil and rock conditions. Kelly drilling can also deal with diameters up to 10 ft (3.00 m) and bigger or depths of more than 330 ft (100 m). Nonetheless, there is a concern about Kelly drilling as it is a relatively slow installation process. Therefore, an alternative piling method like Cased CFA (CCFA) Piles (Cased Auger Cast Piles) provides a significant advantage in terms of installation performance, schedule and cost saving potentials. Major application for the Cased CFA system is the secant pile wall construction. Against the traditional secant pile wall systems like fully cased bored piles or CFA secant piling the Cased CFA secant pile wall system has the advantage in cost and time against the fully cased system and in quality against the standard CFA system. This paper will describe the methodology and installation process in general as well as first reference projects carried out in the United States. This paper will present the results in cost and schedule saving using this method. In addition, we will also describe the limitations of this method. INTRODUCTION In the changing construction environment, companies are searching for new technologies or improvement of existing technologies to complete their projects in shorter time frames to provide a good economic solution. Especially with the focus of increasing urbanization, the aim of fast construction becomes more and more important. When thinking of piling, most people will have the same picture in mind: that of a hydraulic drill rig working in Kelly drilling mode; however, the perpetual drill rig development provides a number of options for the execution of specialist foundation projects, either for foundations or for pile walls when using single pass applications like CFA, Cased CFA and Full Displacement Piling (FDP). Single pass means, in general, that the tool is pushed and rotated into the ground to the final depth in one stroke. After reaching the final depth, concreting is started and concrete is pumped continuously while the tool is withdrawn.

Jan 1, 2019

By Kamil Nuzha, Jianchao Li, Bashar S. Qubain

"The Philadelphia Water Department is rehabilitating Belmont Raw Water Basin. As part of this work, a 500-ft long, temporary cofferdam was designed to retain 35 ft of combined water and soil at the western half during the reconstruction of the eastern half. A cofferdam that comprises two integral rows of sheet piles was selected to take advantage of the soil’s weight between the sheet piles for increased stability. To fine tune the design, a geotechnical investigation was carried out to verify the subsurface conditions and, in particular, the top of rock variations along the centerline of the cofferdam. A detailed finite element analysis was performed based on the subsurface findings and incorporating the construction sequence to evaluate the behavior of the cofferdam at the following stages: installation of tie rods to connect to the two rows of sheet piles; partial excavation and installation of tiebacks; complete excavation of the east basin, and demolition of the cofferdam. Inclinometers and survey markers were installed every 100 ft along the cofferdam and were monitored throughout construction. The deformation measurements were in good agreement with the finite element results.INTRODUCTIONThe Philadelphia Water Department (PWD) Belmont Raw Water Basin is located at the intersection of City Line and Belmont Avenues in Philadelphia, PA. The facility actually contains two raw water basins, east and west, separated by an earthen dividing dike. Water leakage at the bottom of the basins and through the dividing dike together with increasing demand for a larger storage capacity dictated the replacement of the wide earthen dike with new narrower concrete structure. The temporary cofferdam was designed for a two-year period to facilitate excavation support, water cutoff, removal of the existing earthen dike and replacing it with a new concrete dike. During this construction sequence, the water level in the west basin had to be maintained at or near its full capacity.Various excavation support systems were considered for this project prior to the selection of a double wall sheet pile cofferdam. Fig. 1 shows a plan view of the cofferdam and the new dividing dike. A typical cross section of the two structures is shown in Fig. 2. Double row sheet pile walls are commonly used as both temporary and permanent retaining systems in open water applications such as construction works, quaywalls, breakwaters and revetments for storing industrial waste as indicated by Ohori, et al. (1984), Ohori et al. (1988), and Khan, et al. (2001). There are many advantages to double row sheet pile systems as recognized by Ohori, et al. (1984; 1988): (1) It can be installed and removed in the presence of water easily and quickly; (2) it provides stability with small width to height ratio, utilizing the existing soils between the installed sheet pile rows; and (3) it serves well as a means for water cutoff. These advantages meet the specific project requirements."

Jan 1, 2016

By Daniel Ruffing, Charlie Krug

In recent years, the chain-style trencher has been proven a valuable tool for installing vertical walls on challenging sites where conventional methods may be less desirable. Like many tools, trenchers are most effective when used with the right application. Trenchers are commonly used for applications that could also be completed with conventional slurry trenching; low-permeability cutoff walls, collection trenches and permeable reactive barriers (PRBs). Drawing from a wealth of experience with conventional slurry trenching and the trencher, this paper compares and contrasts the technical considerations, treatability, installation, performance, and lessons learned for recent projects.

By Sun Gengsheng

Geotechnical properties of soils, usual types of pile foundations, pile capacity, calculation of settlements of pile foundations, usual types of retaining structures for deep excavation, stability analysis of retaining structures and Anti-buoyancy soil anchors in Shanghai.

Jan 1, 1991

By Marcelo Chuaqui

We certainly have the data to back calculate it. I must admit that I haven't, at the moment my priority is not on what is the stiffness of the jet grout but is making sure that the jet grout is really there. It's a bit like what Stuart Littlejohn was talking about this morning in terms of grouting on the dams a small window causes a big problem so it's having the jet grouting there at all, at the moment must have been my focus rather than just what is the stiffness once you've got it there.

Feb 10, 2003

By Federico Pagliacci

Continuous Flight Auger (CFA) technique represents an important technological advance in the construction of piles in soft soils. The possibility of excavation under the water table with no need for drilling fluids, along with high productivity, have resulted in this technique?s becoming widespread in many countries. However, CFA technology has limitations because of its difficulty in penetrating hard layers and cross strata with cobbles and boulders. In these situations, pile verticality may be an additional problem. The Cased Augered Pile (CAP) technique consists of penetrating the soil with an auger housed in a casing. Two independent rotary heads sliding along the rig mast operate the auger and the casing. By adjusting the height of the casing shoe and auger bit according to soil type, it is possible to drill piles in very severe conditions - in the presence of cobbles and boulders - and to socket the pile into the rock. The use of a steel casing enables improved pile verticality. Therefore, the CAP technique is also used to construct secant piles to be used as diaphragm walls. The limitations of this technology are the depth, usually no more than 27 m (88 feet), and the size of the rig that supports the drilling tool, no less than 70 t (77 short tons) in working conditions. This paper illustrates CAP technology, the drilling system, and the characteristics of concrete and steel reinforcement and offers a case study of the Palermo-Carini second railway line, which used CAP to construct the new 30 km (18.6 mi) railway line, 20 km (12.4 mi) of which passes through the very congested downtown area of Palermo. More than 300,000 m (186.4 mi) of piles have been drilled in dense calcarenite formations with unconfined compressive strength of 15-25 MPa (2,200-3,600 lb/inch2), soft clay, and silt formations.

By Federico Pagliacci

Continuous Flight Auger (CFA) technique represents an important technological advance in the construction of piles in soft soils. The possibility of excavation under the water table with no need for drilling fluids, along with high productivity, have resulted in this technique’s becoming widespread in many countries. However, CFA technology has limitations because of its difficulty in penetrating hard layers and cross strata with cobbles and boulders. In these situations, pile verticality may be an additional problem. The Cased Augered Pile (CAP) technique consists of penetrating the soil with an auger housed in a casing. Two independent rotary heads sliding along the rig mast operate the auger and the casing. By adjusting the height of the casing shoe and auger bit according to soil type, it is possible to drill piles in very severe conditions - in the presence of cobbles and boulders - and to socket the pile into the rock. The use of a steel casing enables improved pile verticality. Therefore, the CAP technique is also used to construct secant piles to be used as diaphragm walls. The limitations of this technology are the depth, usually no more than 27 m (88 feet), and the size of the rig that supports the drilling tool, no less than 70 t (77 short tons) in working conditions. This paper illustrates CAP technology, the drilling system, and the characteristics of concrete and steel reinforcement and offers a case study of the Palermo-Carini second railway line, which used CAP to construct the new 30 km (18.6 mi) railway line, 20 km (12.4 mi) of which passes through the very congested downtown area of Palermo. More than 300,000 m (186.4 mi) of piles have been drilled in dense calcarenite formations with unconfined compressive strength of 15-25 MPa (2,200-3,600 lb/inch2), soft clay,

Jan 1, 2017

By Kanagarajah Ravishankar

Drilled shaft (caisson) foundations are extensively used in the past. In the central part of New Jersey, the soils consist of silt and clayey silt overlying Triassic age shale bedrock. The shale is friable and generally severely weathered and highly fractured. The shale crumbles readily into small fragments. In general, the shale is encountered in shallow depth. Subsurface investigations indicated that the upper part of the shale is very soft, highly weathered, and able to advance through soil exploration methods. The underlain formation is relatively hard and required rock coring techniques for sapling. Individual core recoveries ranged from 10 to 100 percent and Rock Quality Designations (RQD) vary from 0 to 90 percent. Although several methods available to estimate the axial capacity of drilled shafts, it is a difficult task for the designer choose the suitable method due to self disintegrate nature of the shale. In the recent years several bridge foundations have been constructed using drilled shafts founded on shale rock in the vicinity of the central New Jersey. Based on load tests carried out on drilled shafts during construction, subsurface exploration, and laboratory tests, suitable methods for determining axial capacity of drilled shafts is analyzed. This paper presents the findings of the field tests and suitable methods to determine the axial capacity of drilled shaft founded on soft shale. Key words: Drilled shaft, axial capacity, Osterberg load test, shale.

Jan 1, 2006

By Juhyung Lee

Recently, large diameter drilled shafts are often used for foundations of large-scale marine bridges with high capacity and required to resist lateral loads. Steel casings are essential in supporting the hole-diving concrete installation of the drill shafts constructed in the sea. The casings, however, are usually not considered as the structural elements and their load bearing capacity is often overlooked in the design of drilled shafts. As the diameter of drilled shafts becomes larger, there are higher demands for more efficient and economical design of large-scaled drill shafts in the sea. Steel-concrete composite columns are popular for the superstructure of bridges, and the outer steel attached to the shaft increases the shaft resistance through confining the concrete. In this study, the lateral resistance of steel-concrete composite drilled shafts was evaluated quantitatively based on the numerical analysis. When steel casings are used as structural elements such as the composite columns. Ultimate lateral bearing capacity of composite drilled shafts with various diameters was numerically calculated through the 3D finite element analysis. For that, elasto-plastic model with the perfect plasticity is involved to capture the ultimate load. A commercial FEA program, MIDAS-GTS, is used in this study. Real field conditions of the west coast, Korea were examined to set up the ground conditions and pile lengths required for this parametric studies. Detailed characteristics of the stress and displacement distributions are evaluated for the better understanding on the mechanisms of the composite shaft behavior.

Jan 1, 2008

By Dr. Anup Kumar Mandal, Partha Roy, Shuvranshu Kumar Rout, Dipak Mandal, Biswajit Das

Installation of a new scalping station with bunker, apron feeder, scalping screen, ramp -retaining wall and approach bridge was planned in an existing integrated complex of phosphate fertilizer at a remote place in West Africa. Rock phosphate ROM, transported from mines by a combination of 100 Ton and 150 Ton dumper, would be fed to a steel bunker having capacity of 180 m3. Different options were studied for retaining wall at the junction of ramp and approach bridge. Initially options with conventional RCC Retaining Wall, Gravity Retaining Wall with Precast Concrete Blocks and Reinforced Earth walls were studied. Option with Reinforced Earth was selected as this option was much more cost effective compared to other options. But real engineering challenges cropped up when competent execution contractors were not available nearby the site. To minimize the cost, an innovative option with Stepped Retaining wall was then studied. Geotechnical parameters of native soils, selected for the construction of the approach ramp were determined and it was found that with available poor geotechnical parameters of the native soils, design of stepped retaining wall would not be feasible with respect to available bearing capacity, subjected dead load, live load, operational load and earth pressure. A conscious effort was then made to make the design feasible by improving the geotechnical parameters of the retained earth of ramp near the retaining wall. In view of that, mix design with locally available materials like Silexite, Sand, Laterite, Gravel and Silt at different proportions was made and samples were tested in the laboratory to determine relevant geotechnical parameters. Based on the test results, a suitable mix was selected that had high shear strength, enhanced bearing capacity and improved coefficient of earth pressures. Design of stepped retaining wall was then made with the selected construction materials and construction completed. The plant was successfully commissioned in December. 2021.

Sep 1, 2022

By Ben C. Gerwick

Large diameter steel tubular piles installed vertically or on a slight rake, offer many advantages as the foundations of major overwater bridge in regions of high seismicity. By proper selection of diameter and wall thickness, an optimum balance between stiffness and strength can be achieved. Under strong seismic motion, the piles will deflect and bend so as to reduce the acceleration forces transmitted to the superstructure, while still limiting drift. A major advantage of this concept is that the mass of the footing block is significantly reduced from that of the conventional pier. The design of the footing block requires great care in order to transfer the high shears and moments. Where the soils consist of significant depths of sediments, the kinematic interaction of soils, piles and structures must be considered. Moments will be a maximum just under the footing block. Filling the top portion of the pile with concrete will prevent local buckling and assure ductile behavior even under overload. Typically the piles will be long, with most or all of their support furnished by friction and will require the use of very large pile hammers to achieve the required capacities. Where the piles are founded on rock or in hardpan, sockets will be drilled and filled with reinforced concrete. For these piles, high moments can occur both at the head and just below the rock surface, so the concrete infill should extend the full length. This paper describes the use of tubular piles driven through the deep silty sands of the Jamuna River, Bangladesh, and also where socketed into the near-surface rock for the mail pylon pier of the new San Francisco-Oakland East Bay Bridge in California.

Jan 1, 2013

By Paul Suver

The closed loop standing column well (CLSCW) system uses a closed circuit of water to develop the same thermal heat exchange characteristics that are achieved from traditional open circuit standing column well that uses the ground water directly. Pipe pile and pipe anchor foundations can be used as CLSCW components for ground source heat exchange. New data gathering and analysis techniques and equipment installed in the heat pumps allow any mechanical engineer to design the system without specialty engineering equipment and certifications.

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 Paul Suver

"The closed loop standing column well (CLSCW) system uses a closed circuit of water to develop the same thermal heat exchange characteristics that are achieved from traditional open circuit standing column well that uses the ground water directly. Pipe pile and pipe anchor foundations can be used as CLSCW components for ground source heat exchange. New data gathering and analysis techniques and equipment installed in the heat pumps allow any mechanical engineer to design the system without specialty engineering equipment and certifications.CLSCW Description:Closed end steel pipe of varying outer diameter (O.D.) is installed by various technologies at varying depths depending on subsurface geology. The wells are arranged as stand alone wells or in groups joined in parallel or in series or in a combination of both. These pipes may also serve a dual function as foundation supports, deep foundation pile, anchors or earth retention components. These wells are then internally coated to minimize corrosion. The wells are then plumbed and capped to create a vessel equipped with a supply and return water line.The stand alone well or group of wells is then used as a ground heat exchanger for a ground source heat pumps located in or around the building.The ground source heat pumps provide heating and cooling to the building either with a traditional ducted distribution system or with radiant heating and cooling. These systems can reach efficiencies three times greater than traditional gas fired heat sources and five times greater than traditional air conditioning sources."

Jan 1, 2017

By Dale Berner, Michael O’Sullivan

"This article focuses on lessons learned from innovative designs including in-the-wet construction methodology and modified foundation conditions, for two United States Army Corps of Engineers (USACE) megaprojects. Olmsted Dam FoundationThe over $2 billion Olmsted Dam on the Ohio River is currently under construction 16 mi (29.6 km) upstream from the confluence with the Mississippi River. The project is under the jurisdiction of the Louisville District of the USACE. It will consist of an 800 ft (244 m) long tainter gate section, a 1,400 ft (427 m) navigable pass, two boat abutment sections, a fixed weir section, and upstream and downstream scour protection. The Olmsted Dam and its two 1,200 ft (366 m) locks, which were built in 2002, will eventually replace both Locks and Dam #52 and #53, both built in 1929, and thereby bring significant benefits to the Ohio River navigation system.In 2002, the Jacobs/COWI JV completed the design of the dam; which was an engineering challenge for several reasons. A significant consideration was its proximity to the New Madrid Fault, which could impose an 8.4 Richter scale seismic event on the structure, which is located in an area of potentially liquefiable alluvium. The extensive seismic analysis performed by the designer included a response spectra analyses, lateral pushover analyses of pile foundations, hydrodynamic added masses, pile group effects, and the development of kinematic motions as a result of the soil-pilestructure interaction."

Jan 1, 2016

By Dan A. Brown, Rich A. Lamb, Paul J. Axtell

"Over the last 10 years, the Minnesota Department of Transportation (Mn/DOT) has had a very active program of replacing many major bridges, large structures spanning the Mississippi River. The deep foundations for these new structures include both drilled shafts and large diameter open-ended driven steel pipe piles. Most of these projects included load tests, both axial and lateral.The geology of this area of Minnesota includes some interesting foundation challenges, including highly organic and compressible very soft silts and clays to very dense sand and gravel overlying sedimentary bedrock. In some cases scour requires embedment into rock, and the bedrock formations may range from very soft sandstone to very hard dolostone. Artesian groundwater conditions can sometimes complicate drilled shaft construction, but the rock is otherwise very favorable for drilled shafts. Experience with the open-ended driven steel pipe piles (typically 42 and 48 in, 1.07 and 1.2 m diameter) suggest that these piles most often penetrate even dense granular materials to achieve bearing on rock. Experiences with drilled shafts socketed into the soft sandstones demonstrate that these rocks provide very favorable conditions for drilled shafts, so long as suitable construction practices are followed. Here we present several recent case histories regarding the foundation design and construction of major bridge projects in the vicinity of Minneapolis, Minn., including the Wakota Bridge, the I-35W replacement, the Lafayette Bridge, the Hastings Bridge and the St. Croix Bridge. Some lessons learned from construction and load testing of both types of foundations are described along with implications for design in similar soil and rock conditions."

Jan 1, 2013

By Scott A. Walker, Gabriel J. Alcantar, Brian Zuckerman, Ramin Golesorkhi

"The new San Francisco 49ers Levi’s Stadium is part of the next generation of sporting facilities. Constructed in Santa Clara, Calif., the new structure has 68,500 open-air bowl seats and includes a 7- story tower housing more than 150 suites. The overall project includes the stadium structure, elevated open pedestrian walkways, commercial community space, three new pedestrian bridges and improvements to the adjacent light rail station. Sustainable design for the project includes a green roof, photovoltaic panel and a ground source geothermal system. Stadium-wide next-generation Wi-Fi capability is another feature. The design-build project team included HNTB (project architect), Magnusson Klemencic Associates (MKA, structural designer) and a joint venture of Turner Construction and Devcon Construction (TDJV, general contractor).During preconstruction, the 49ers’ original design team and the design-build team formed later worked together to facilitate communication and provide continuity. This helped to meet the project’s aggressive schedule. Working directly for the 49ers, with the design-build team, Treadwell & Rollo (T&R) served as the geotechnical engineer of record for the project from preliminary to final design and through construction. Although not contracted directly to TDJV, the stadium ownership encouraged direct interaction between T&R and TDJV and improved responsiveness to geotechnical issues during design and construction.Subsurface ConditionsThe new stadium lies within the Santa Clara Valley, a deep alluviumfilled basin resulting from historic movement on the active and potentially active strike-slip and thrust faults that bind the valley. The valley is filled with Holocene age (approximately 11,000 years old to present) alluvium, consisting of levee and basin deposits, with bedrock more than 750 ft (229 m) beneath existing ground surface. The stadium site is between two of the highly-active faults in California, the Hayward Fault 6.8 mi (11 km) northeast, and the San Andreas Fault about 11.8 mi (19 km) southwest."

Jan 1, 2014

By David R. Shields, Michael T. Bracher

"The $330 million (U.S.) Dana-Farber Cancer Institute’s Yawkey Center for Cancer Care (Yawkey Center) sits in the heart of Boston’s Longwood Medical Area. The Yawkey Center is a cutting-edge cancer care facility that houses Dana-Farber’s adult clinical care and clinical research programs. Standing 14 stories above grade, it includes 7 stories of underground parking extending 75 ft (23 m) below ground. The structure is on a 198 by 186 ft (60 by 57 m) site sandwiched between Dana-Farber’s 13-story Richard A. and Susan F. Smith Research Laboratories Building, the Medical Area Total Energy Plant (MATEP), Jimmy Fund Way, and Brookline Avenue, a busy four lane artery through the heart of the Longwood Medical Area. Together with Simon Design Engineering, the project structural engineer, GEI Consultants designed an innovative foundation and excavation support system to isolate the building from ground vibrations generated by the adjacent MATEP power plant. In effect, the Yawkey Center is a 21-story free-standing structure that starts 7 stories below grade.The MATEP facility provides power for 9 million sq ft (840,000 sq m) of occupied space in the medical area. There are six 32-cylinder diesel engine generators in the facility that produce low-frequency ground vibrations in the 10 Hz range, similar to the natural frequency of typical building elements. The resonant response of the Yawkey Center building structure to these ground vibrations would affect the performance of sensitive medical research equipment and cause an unacceptable environment for clinical care.The soil profile at the site consists of stiff clay, fine sand, glacial till, and bedrock consisting of hard metamorphosed conglomerate. In-situ measurements of ground vibrations performed in boreholes showed that there was little attenuation of the vibrations with depth in the soil layers overlying the bedrock, but the vibration amplitude in the bedrock was markedly lower than in the overlying soil. Based on this data, an innovative foundation system was designed to support the building on bedrock located up to 110 ft (34 m) below ground surface, while isolating it from the surrounding soil. This was done by physically separating the below-grade parking garage floors from the perimeter foundation walls to create a free-standing structure supported on the bedrock"

Jan 1, 2012