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By Mark Maday

As part of the I-94 North-South Corridor reconstruction program, the Wisconsin Department of Transportation (department) is reconstructing the Mitchell Interchange in Milwaukee, Wisconsin. Located on the south side of Milwaukee near Mitchell International Airport, The Mitchell Interchange interconnects I-94, I-43 and I-894. Reconstruction began in 2009 with the letting of the first advance contract for local crossroad bridge reconstruction. A second advance contract for construction of collector-distributer roads on each side of the I-94 mainline was completed in 2010. The main contract involving reconstruction of the core of the Mitchell Interchange was let in the summer of 2010, and is scheduled to be completed by the end of 2012. The core contract includes construction of three cut and cover tunnels along two system interchange ramps. Construction of the three tunnel structures is on the critical construction path. The contract includes an interim contract completion date that requires the tunnels to be open to traffic by the end of 2011. A top down method of construction using drilled shaft secant piles for the sidewalls of the cut and cover tunnel structures was selected as the preferred structure type to address subsurface and construction schedule challenges. The department identified in pre bid coordination that no cost reduction incentives would be reviewed or accepted for changes in tunnel wall type. A major component of the tunnel structures requires the installation of 1,500, 4-foot diameter secant piles. This paper presents mitigation strategies to manage construction risks associated with the installation of the secant piles including; prequalification of the secant pile subcontractors, requirement for use of full depth temporary casing, a site specific quality control plan, specifying drilling equipment, and developing a geotechnical baseline report for this critical component of the Mitchell Interchange reconstruction project.

Jan 1, 2011

By Andy Schroeder

Located in Hamilton, Ontario Canada, Berminghammer Foundation Equipment, is a manufacturer of advanced foundation equipment with 30 years of experience. The company is represented in more than 20 countries world wide, maintains an extensive Research and Development team, and has earned a reputation for finding the most practical solutions to the most challenging projects. The vertical travel lead, referred to as "VTL" system, was first developed and patented by C.W. Bermingham in the 1970's. This lead system was developed in response to the fundamental limitations of either a fixed lead or hanging lead system. The fixed lead system is well suited to level job sites with few obstructions and has the advantage of faster positioning of the lead, the hanging lead is very adaptable to different elevations and batter piles but takes much longer to position. Therefore the Vertical Travel Lead was developed to combine the advantages of fixed leads, fast and accurate positioning, with the ability to adjust the height of the lead base up or down. The VTL lead is connected to the boom by a sliding connection which allows the lead to be elevated or lowered below grade. The advantages of the VTL system were recognized by many foundation specialists and they have become the Industry standard in Canada , US Railway Construction , and many parts of the USA.

Jan 1, 1997

By Scott A. Walker, Frank L. Rollo

"The San Francisco Museum of Modern Art (SFMOMA) in downtown metropolitan San Francisco, California, is supported on a mat foundation. Although the mat foundation of the original museum was designed to accommodate a future expansion, the plans for expansion that developed in 2010 required a larger footprint to accommodate the new space requirements of the museum. The new, larger expansion was designed by lead architect Snohetta. It will be a tall 12-story, steel-framed building occupying an area that was once the eastern part of the existing museum as well as two adjacent and newly acquired parcels.As designed, the expansion includes a 30-foot-deep excavation which is surrounded by adjacent buildings and improvements. Because of variable subsurface conditions at the site, geotechnical challenges included mitigating anticipated differential settlement between the existing and new foundations, preventing overstressing of the existing mat foundation, controlling groundwater to prevent settlement of surrounding improvements, and providing temporary support of adjacent structures during excavation for the new basement.To address several of the geotechnical challenges, soil-cement mixed (SMX) ground improvement was recommended by Treadwell & Rollo. However, during contract negotiations and construction, the specialty contractor proposed using jet grouting as an alternative technique for ground improvement. The jet grouting approach was accepted in principal, but when implemented was only marginally successful. Accordingly, the contractor eventually installed SMX panels using a Cutter Soil Mixing (CSM) machine. Because the CSM machine was a late arrival during construction, the contractor was not able to take advantage of the ground-improvement technique to install many of the shoring elements that we had originally recommended (such as the cut-off shoring wall). In the end, SMX panels were installed as ground-improvement beneath the new mat foundation to (1) reduce the potential for liquefaction in clean sand below the groundwater by providing increased rigidity to the soil, (2) reduce the potential for disturbing a weak underlying marsh deposit during construction, and (3) transfer vertical building loads to a layer of underlying dense sand.This paper also discusses the quality control and quality assurance programs that were implemented to check that the ground-improvement techniques used were thorough and complete and provided the required strength to transfer the new foundation loads to the underlying strata."

Jan 1, 2014

By Qi Wang, Zengzhu Kang, Jianguo Liu, Guanglei Liu

"Due to the increase of automotive vehicles, available parking spaces become a new type of limited resource in central cities of China, especially in those old districts without visionary urban planning. Additional mechanical parking in underground space is an efficient solution to provide parking spaces under the situation where the urban space is constrained. Shichahai district is an old protected zone in Beijing which is close to the Forbidden City and there are many Hutong (alleyway) and Quadrangles (courtyard house). No spaces are available for car parking on the ground and all vehicles are parking in Hutong without order currently. The local government plan to do renovation work for this district and improve the residential environment. Several innovative solutions are studied including parking in deep shafts, parking under existing buildings by under-pinned method, parking under buildings by covered excavation method, parking under roads built together with utility tunnel etc. 5000 difference types underground parking spaces are planned to be constructed in the following three years. Project examples are also introduced in this paper. INTRODUCTIONCar parking resources are very limited in central cities, especially in old districts without planning for increasing automotive vehicle volume. Traffic get worse when cars park on the side of the roads or move slowly to find parking spaces. Investigation shows the normal (parking space/ automotive vehicle volume) ratio is about 1.2 in most big cities such as New York, Tokyo and Hong Kong, while this ratio is only 0.5 in Beijing. One solution is to move cars out of central cities. But there are still huge parking requirements for the citizens living in central cities. Shichahai district is an historic protected zone in Beijing which is close to the Forbidden City and there are many Hutong and Quadrangles (refer to Figure 1 for project location). No spaces are available for car parking on ground and all vehicles are parked in Hutong without order currently. The local government had a plan to do renovation work of this district and improve the residence environment. 5000 different types of underground parking spaces are planned to be constructed in the following three years. One project designed and to be constructed by Zhongyan Technology will be introduced in this paper. Other innovative solutions will be introduced briefly as well."

Jan 1, 2017

By Jiwei Duan

The energy transferred from a hammer to the pile top is considered as the effective energy in this paper. The effective energy is related to the pile dimensions, soil and pile-soil interface properties. This relation may be expressed as an equation based on the dimensionless theory. The relationship between pile capacity and effective energy was studied by performing a series of wave equation analyses using a commercial software called GRLWEAP (Wave Equation Analysis Program) by GRL Engineers, Inc. The results show that the pile capacity increases with the blow count when the effective energy is constant, however, it has a little change as the blow count is over 100 blows per foot. The pile capacity decreases as the ratio of pile penetration depth to pile diameter increases if the effective energy is constant. The pile capacity will increase as the pile diameter and wall thickness increases if the effective energy is constant. The pile stickout (pile length above the ground surface) does not have a significant effect on the effective energy and may be neglected. Curves for pile capacity versus effective energy are presented to be used for preliminary hammer selection according to effective energy and hammer efficiency. Finally, a case from PDA testing was studied. Measurements of the effective energy and pile capacity by CAPWAP were presented and compared with the results by GRLWEAP.

Jan 1, 2006

By Mario Terceros H., Bengt H. Fellenius

"ABSTRACTFour strain-gage instrumented bored piles were constructed in a sedimentary, dense to very dense, fine to medium sand in Santa Cruz, Bolivia. Two of the test piles were the normally used bored pile constructed with bentonite slurry and two piles were Bauer Full Displacement Pile (FDP). One of each pair was equipped with the Expander Body, an inflatable steel cylinder that on pressure-grouting provides an enlarged pile toe. Head-down static loading test were performed on three of the piles and a bidirectional test was performed on the fourth pile, a standard pile with Expander Body and a bidirectional cell placed immediately above the EB. The latter pile was tested in 3 phases. First by activating the cell, second, by a head-down test, and, third, by a repeat bidirectional cell test. The static loading tests proved the shaft resistance of the FDP pile to be about twice that of the standard bored pile and that the Expander Body more than doubled the toe stiffness. The strain-gage records showed that the standard bored piles had multiple bulges and neckings, which affected the evaluation of the axial stiffness and load distribution of the piles. The testing programme was used for a prediction event with 60 persons, ahead of the tests, submitting predictions of the load-movement curves for the test piles and also a capacity appraised from the curves.1. INTRODUCTIONOn April 23 - 26, 2013, the First International Conference and Seminar on Deep Foundations was held in Santa Cruz, Bolivia under the auspices of INCOTEC SRL, the UAGRM University, and the Bolivian Association of Civil Engineers and Chamber of Construction. To coincide with the conference, a research study on construction and static and dynamic testing of four instrumented bored piles was undertaken. To ""add spice"" to the conference, a prediction event was organized on the test programme. This paper presents the soil conditions at the site, the type and construction of the test piles, the outcome of the prediction event, and the results of the static tests.2. SOIL CONDITIONSGeotechnical studies comprising SPT and CPT tests with routine laboratory analysis were performed on recovered soil samples. Three SPT boreholes were put down at three of the locations of Pile TP1, TP2, and TP3, at 5.0 m distance from each other. The SPT procedure consisted of manual hoisting of the weight by three crew members pulling on ropes over a pulley supported by a tripod and letting the weight fall by gravity. The groundwater table lies at 3.5 m depth.Figure 1 shows diagrams of the SPT N-indices and the distribution of water content in the three boreholes. The SPT-indices show the soil density to be compact. The average water content is about 15 %, plus-minus a few percent."

Jan 1, 2014

By Dennis Nottingham

Spin-fin pipe piles can develop large loads in tension, thus have evolved as a foundation product of great potential. Currently, over 500 spin-fin piles have been used successfully in dolphins, docks, buildings and bulkheads. Spin-fin piles are pipe piles with plates welded near the tip at a batter-in-screw fashion. Thus, as the pile is driven, the pile screws into position. Tests show this pile type to have highly unusual stress/strain relationships, wherein plunging failure is usually never reached either at normal or large deformations. Tension capacity can approach pile capacity in bearing; thus, large reserves are usually available for tension. Tests have been performed on 8-5/8-inch to 24-inch-diameter piles in silt, sand, and gravelly soil, to provide a broad spectrum of data.

Jan 1, 1990

By Garland Likins

Where soil conditions are favorable, augercast piles have significant economic advantages, but they also have some uncertainty due to the in construction methods. To confirm structural integrity, static testing can be performed on a small sample of piles. Other Non-Destructive Evaluation methods like Pulse Echo are frequently specified for a large percentage of the remaining production piles. However, such NDE methods require testing the pile after the grout/concrete has hardened. If problems are found, then the repair or replacement can be relatively expensive. The confidence in the quality of these piles can be improved by automatically monitoring the grout pumped as a function of depth during the grouting phase of installation. If a low grout volume is detected, the pile can be redrilled and regrouted immediately while the piling rig is still in place and the grout still fluid. This considerably reduces remedial costs. To be effective, such installation monitors must accurately determine both grout volume and depth during installation and be rugged simple to operate. Such an equipment can be of great help to the installation crews. The assurance gained may reduce the need for subsequent NDE tests. The quality of inspection of driven piles depends heavily on the inspection personnel. While inspection is critical in a good installation, it is sometimes assigned a low priority. Inspection personnel in many cases are technicians with little pile experience. They may not understand the project needs or even how the pile driving equipment works. The task is often monotonous and any distraction makes accurate record keeping difficult. In some cases inspection is totally ignored for lack of qualified personnel. Electronic systems can automatically and accurately monitor driven pile installations and include documentation of certain hammer performance parameters. This paper describes equipment available and routinely in use for automated monitoring of both augercast and driven piles and demonstrates applications on typical construction sites. The paper also discusses benefits and limitations of the alternative NDE tests. KEYWORDS: Augercast Piles, Piles, Installation Monitoring, Pulse Echo Method, Integrity Testing

Jan 1, 1999

By Peter J. Nicholson

Since the reintroduction of soil mixing to the United States over 10 years ago, the work installed by soil mixing technology has grown dramatically. From an annual turnover of less than ten million dollars per year the volume of soil mixing put in place has grown to an estimated $40 million per year in the year 2000. The majority of work done to date has involved walls, either for excavation support, permanent retaining structures or hydraulic cut-off walls. The other major use for soil mixing has been for mass stabilization of soils whether for isolation of contaminants or for retaining structures. This paper will discuss the uses of and costs of typical soil mix structures. BACKGROUND Soil mixing is defined as the in-situ combining of reagents, typically cement, with native soils, the purpose being to modify or improve the ground. This history of soil mixing covers only the use of cement slurry, aggregated with soil in-situ by mechanical mixing methods only. Soil mixing by use of high-pressure hydraulic means, also known as Jet Grouting, will not be discussed. In addition this will not cover ex-situ (above ground) mixing, or mixing dry reagents with soil. Only mixing applications for building, civil and heavy construction applications will be discussed, with only passing reference made to uses of soil mixing for environmental remediation work.

Jan 1, 2001

By N. Shariatmadari

In recent years, determining bearing capacity of piles from in-situ testing data as a complement of static and dynamic analysis has been used by geotechnical engineers. In this paper, different approaches for estimating base bearing capacity of piles from SPT data has been compared and evaluated. A new method for pile base bearing capacity in sand is proposed using SPT records. Data averaging, failure zone extension, and plunging failure of piles have been addressed in the proposed approach. A data bank comprising 10 full scale static load tests on instrumented piles and 26 dynamic tests, analyzed with signal matching technique by CAPWAP software, was used for validation. The SPT data that was performed close to pile locations is also included in the data base. Comparison of current methods by error investigation with Log-Normal approach demonstrates that the proposed method predicts pile base capacity with more accuracy and less scatter in comparison to other methods.

Jan 1, 2006

By Christopher J. Pacitto

This paper presents a case history of an engineered, monitored, and tested program that provided an effective and satisfactory basis for the completion of pile foundations for Twin Dolphins 1 at La Peninsula Condominiums located in the Isles of Capri in southwest Florida, U.S.A. An 8-story building (withl-story parking underneath) along with recreational facilities (such as a swimming pool and tennis courts) had been planned for final construction. Following an evaluation of various foundation alternatives, a precast prestressed concrete (PPC) pile-supported system was selected. The building foundations were designed for pile capacities of 445kN (50 tons) and 890kN (100 tons) in compression and 133kN (15 tons) in uplift. A test pile program was performed to provide site-specific pile driving data, verify design assumptions, determine production pile lengths, and evaluate pile driving criteria. A total of 24, 356 mm (14-in.) square, 19.8 m (65 ft) PPC concrete piles were driven and dynamically load tested utilizing a Pile Driving Analyzer (PDA) within the building limits. Dynamic monitoring during probe pile installation and restriking was performed to estimate the ultimate capacity of the piles and to evaluate driving stresses during installation. CAPWAP analyses were preformed on PDA data to better estimate pile capacity, resistance distribution, and predict pile freeze (increase in pile resistance with time) and thus optimized the production pile lengths. Upon completion of probe pile installation, 12 of the probe piles were tested using the Pile Echo Tester (PET) function of the Pile Integrity Sonic Analyzer (PISA). PET testing was performed to evaluate the integrity of piles which had exhibited high driving stresses during PDA testing. Information gathered during the probe pile driving program was effectively utilized as part of the overall quality control program to install a total of 539 PPC piles (including 24 probe piles) within the building limits at the project site to depths ranging from 9.1 to 19.8 m (30 to 65 ft) below the existing ground elevation as part of the foundation support system. Prior to installation of probe or production piles, a termination criterion was established using 1-dimensional wave equation analyses in addition to the design pile embedment requirement. The predicted pile capacities compared very well with the capacities from the CAPWAP analysis for probe piles. Use of geotechnical instrumentation and PDA assisted technology enabled each foundation support element to be constructed to its optimum capacity and at optimum cost. Furthermore, by using PDA the consultant was able to quantify a difficult to measure geotechnical phenomenon termed "pile freeze" which eliminated costly overdriving and unnecessary splicing of piles.

Jan 1, 2002

By Bruno Gemmi

The objective of the ? 200 million ($280 million) project Parma Railways Station-Urban Transformation was the reconnection of the North and South parts of the town by constructing an 80 m (250 ft) wide sunken artery passing under the four double railway tracks of the station without any impact on train traffic. The site of the project, adjacent to the Parma River, presented water seepage problems at any excavation depth. The use of conventional large diameter bored pile machinery was not allowed by the Railway Authority because equipment dimension and construction phases do not comply with train traffic safety regulations. Foundations for the bypass were thus constructed by minipiles nested into jet-grouted soil using machinery operating within the existing head room and at a safe distance from the tracks. Jet-grouting treatment reached depths of 25 to 28 m (80 to 90 ft) from tracks? grade and embedded minipile-heads were terminated at 2 to 3 m (6.6 to 10 ft) below grade. Load tests on minipiles were pushed to failure. Failure occurred at a 240 t (265 t) load without breakage of the bond between the jet grouted soil and the minipiles. A 0.93 MPa (135 psi) shear resistance ??? between minipile steel casing and the jet grouted soil was measured prior to the failure of the steel casings. Overall measured foundation settlements were well within expected values and were considered insignificant.

Jan 1, 2011

By Mohamad Hussein

Low strain dynamic tests are performed to evaluate the structural integrity of driven or cast-in-place concrete piles. This type of testing requires minimal pile preparation, and is simply performed by attaching an accelerometer to the pile head and striking the pile head with a hand held hammer. The measured data is processed by a dedicated system, inspected for wave reflections, and interpreted based on one dimensional wave propagation theory. Piles are normally tested shortly after installation so that problems can be identified early and corrective measures taken before construction of the superstructure. However, evaluation of existing foundations is occasionally required. Often, pile installation records are not available rendering impossible any rational foundation reanalysis. This paper discusses three case histories where low strain dynamic measurements allowed determination of pile lengths and structural integrity under existing structures where pile heads were not accessible.

Jan 1, 1992

By Jim Frazier

Tradition has often dictated low design load stresses on piles. Such traditions often developed prior to modern static or dynamic pile testing methods and perhaps result from a few limiting situations. These low stress limits were then broadly applied, even in cases where the piles could carry substantially higher loads. With sufficient testing to prove the design, higher design loads may present significant overall savings to the project owner. The cost of the testing then becomes an insignificant cost compared to the potentially great benefit of increased pile loadings. To confirm higher load possibilities for driven piles, the pile is tested either statically or dynamically. Further savings and increased testing efficiency result from remote dynamic pile testing. This paper presents a project where design stresses were considerably increased as a result of additional testing and use of remote dynamic pile testing equipment.

Jan 1, 2002

By Eric S. Lindquist

High groundwater levels combined with variable soil and rock profiles present challenges to the design and construction of deep excavation support systems. Increasingly, secant piling techniques are the preferred technical solution for shoring in these cases. Recent developments in drilling equipment, tooling and procedures allow cost-effective construction of deep, overlapped pile systems to tight tolerances in extremely difficult ground conditions. This paper summarizes critical design considerations for secant pile shoring systems, detailing recent advances in installation procedures and verification techniques that allow secant piles to be used for an expanding range of project conditions. Technically- and commercially-viable secant pile shoring designs require that stringent drilling tolerances be achieved in order to successfully provide combined structural support and groundwater cutoff systems, particularly for unreinforced circular secant pile shafts acting in ring compression. Modern drill rigs and tooling can advance fully cased shafts in geotechnical conditions which range from cohesionless soils below the groundwater table to hard rock, within a single drillhole. Down-hole instrumentation provides verification that tolerance requirements are met and allow secant pile shoring to be used at sites previously considered unacceptably risky. In California, secant pile shoring systems are being used for excavation depths of over 100 ft (30 m) on projects with challenging site conditions. Two case studies are presented detailing severe geotechnical conditions and excavation depths which represent the regional state of practice in secant piled excavation support. These projects provide real world examples of the design, construction and construction verification techniques that permit secant pile shoring to be used in more demanding geotechnical conditions and to greater depths than ever before.

Jan 1, 2011

By W. J. Grose

The Embankment Place office development over the platforms of Charing Cross Railway Station in London has presented many interesting and unusual problems to the engineers involved with the project. The main structure is supported on widely-spaced columns which penetrate the station platforms and underlying vaults, calling for high capacity foundations built in severely restricted spaces. Hand-dug underreamed piles were chosen. Whilst a conventional design approach was taken to size the piles, a detailed appraisal of ground movements was made to explore the effects of the new building loads on the existing foundations, not only beyond the site perimeter but also those amongst the new foundations. Before construction of the pile proper could take place, it was necessary to sink a caisson through the upper unstable and water-bearing soils. This being identified as a high-risk item, a full-scale trial was carried out prior to embarking on the main works. The twenty-one hand-dug piles were 2.5m diameter, over 30m deep and belled out to between 4.5m and 6.6m.

Jan 1, 1989

By Michael Arnold, Bob Faulhaber, Joe Nichols

"Center Hill Dam is a critical part of the infrastructure controlling floods at the Caney Fork River and reducing flood levels at the Cumberland, lower Ohio and Mississippi Rivers. The Center Hill Dam Foundation Remediation Project was necessary to address Karst features in the foundation rocks and observed signs of distress of the dam. From 2011 to 2014 BAUER Foundation Corp. (BFC) performed deep foundation works for this project. The executed features of work include the installation of two walls. The first wall extends throughout the clay embankment into the underlying rock to provide encasement during the construction of the second wall. Its width of 7.4 feet makes it the widest diaphragm wall ever installed. The second wall is the actual seepage barrier and provides a continuous 2- feet wide wall. It extends through the first wall into the underlying rock and is up to 300 feet deep. The paper introduces the project, the requirements specified by United States Army Corps of Engineers (USACE) for encasement and barrier wall and the approaches taken by BFC. It discusses the ground conditions and describes the excavation equipment as well as the excavation methods used. A special focus is put on the steering capabilities of the hydrocutter equipment and the verticality performance.PROJECTBeginning in 2011, BFC was tasked by the USACE with the installation of a seepage barrier/cutoff wall at the Center Hill Dam Foundation Remediation project under a partially performance based specification. The remediation was necessary due to karst features in the foundation rocks and observed signs of distress, which led USACE to rate the dam with the most critical dam safety action classification (DSAC I). The executed features of work include the installation of two walls. The first wall, an encasement wall, extends vertically through the clay embankment and is embedded minimally into the underlying bedrock to provide embankment stability during the construction of the second wall, the barrier wall. The encasement wall is constructed of overlapping panels 7.4 feet (2.25 m) wide, which is the widest diaphragm wall ever installed, and up to 210 feet (64 m) deep. The second wall is the seepage barrier and provides a continuous 2 feet (0.6 m) wide wall consisting of overlapping panels. It extends through the encasement wall into the underlying bedrock and is up to 307 feet (93 m) deep. BAUER BC40 and BC50 hydrocutters mounted on MC96 and MC128 foundation cranes were used to perform the majority of the works (Figure 1). Excavations were performed under bentonite slurry (encasement wall) and water (barrier wall) and concrete was poured with the tremie method. Adding to the challenges, the project had to be executed in an environmentally sensitive area. Based on the high risk, a special focus was put on monitoring, quality control and geometric accuracy. The WallTracker information management system was used to share all relevant data between BFC and USACE (Roff et al. 2014)."

Jan 1, 2017

By Mohammed Z. Islam

As cities are growing all over the world, the need for urban transportation facilities are on the rise. Designers (of these facilities) today are faced with a number of constraints for their design, of the most is the space limitation and impact of new construction activities to the community. A typical subway station, as the focus of this paper, is approximately 600 to 1000 feet long, 50 feet wide and 2 to 3 story high. With such a large volume of construction activities, it is easily realized why underground stations are becoming obvious choice for larger cities eventhough the cost could be 2 1/2 to 3 times as much as an aerial station and 4 to 5 times that of an at-grade station [O'Neil et. al.(1977)]. Since cost is an important factor which is always increasing, therefore, the designer should have a good planning, consider alternatives for design and come up with a realistic design with minimum impact to the community. This paper is about the geotechnical considerations that the designer should be aware of. PLANNING A 1977 report [O'Neil et. al.(1977)] on the construction costs for a number of underground subway stations indicate that about 4 0% of the cost is site-controlled, 35% is structural items, and 25% is finish and equipment. It is seen that of opportunity exists for cost savings in the site selection and proper use of the site. Once the site is selected, the cost of construction become controlled by urban conditions at the site, geotechnical conditions, station size and depth. Therefore, the design-solution is very much site-specific. The geotecnical designer should collect the following information at the early phase of the design:

Jan 1, 1993

By Stanley A. Schwartz

In the Piedmont, heavily loaded structures are generally supported by either drilled piers or one of several pile types. The choice of drilled piers or piles is typically one of comparative costs. The cost of a drilled pier foundation is usually the more difficult to predict because of the greater impact that variable conditions and construction monitoring have on cost. Poor specifications, related to the drilling equipment, procedures and bearing level, can also result in large cost extras. In the southern Piedmont, straight shafts are typically extended down to hard rock to achieve primary support in end-bearing: when bells are required, they are often constructed manually. In some eastern and northern Piedmont locations the thickness of the decompossed rock zone is significant and considerable skin friction can be mobilized. Typically piers are constructed in holes temporarily cased with steel liners. The bottom is cleaned of loose material and water, and then evaluated by a geotechnical engineer to confirm the design bearing pressure (and friction, where appropriate) or recommend alternative construction measures.

Jan 1, 1988

By Patrick E. Durnal

A joint venture of Ben C. Gerwick Inc., Sverdrup (now Jacobs) and DMJM (now DMJM Harris) designed the $779 mill seismic upgrade of the Richmond - San Rafael Bridge over the San Pablo Bay in the San Francisco Bay Area and provided construction support to Caltrans. Construction of the marine foundation retrofit was completed by a joint venture of Tudor Saliba/Tidewater/Koch-Skanska and their subcontractors: Pomeroy Precast Construction, AGRA Foundations, Dutra Construction and Vortex Divers. Construction management and inspection was performed by Caltrans with support of various consultants.

Jan 1, 2013