Breaking Down of Concrete Piles

The breaking down of concrete piles is an essential part of the construction process, and a subject that often is not given sufficient early thought in the planning of the piling works. The Federation of Piling Specialists (www.fps.org.uk ) reminds us that the adoption of a suitable pile breaking method can result in operational savings and, most importantly, will address and reduce potential health and safety issues. Bored cast-in-place concrete piles always should be cast to a level above the specified cut-off such that, after trimming, a sound concrete connection with the pile can be made. Continuous-flight auger piles and any other type concreted or grouted through the auger stem during extraction always must be concreted to the commencing surface level. Pre-cast concrete piles should be driven such that the pile head level will provide sufficient reinforcement projection after trimming.

The Mr Cropper CFA Cropper can reduce an average 12-inch circular cast in-situ concrete pile to the required level in as little as three minutes.

Project Profile

Large-diameter Caissons

John Jay College in Manhattan currently is undergoing a $457 million expansion. The project began in May 2007, and includes the construction of more than 1000,000 square feet of structural concrete, involving more than 180 caissons from 20 inches to 36 inches in diameter. The Posillico Group, headquartered in Farmingdale, N.Y., was chosen to perform the foundation work. The project site is the former location of a gas plant, and is situated on property with a highly varied geology and considerable contamination from its former industrial use.

The site required demolition of an existing roof slab spanning existing Amtrak railroad lines, and three caissons needed to be installed within the Amtrak right-of-way. The project was further complicated by environmental contamination and wet soil conditions. Additionally, significant changes were made to the contract scope during construction to facilitate future vertical expansion of the college. Complicating the planning and development of the structural piles wereas the highly variable geology and rock contours that meandered inconsistently throughout the site. Unexpected obstructions, debris and unsound rock also were found throughout the site, which required implementation of rock sockets, caisson splicing and reinforcing.

Key to Posillico meeting these challenges was the commitment to continue to plan, train and prepare its workforce for working safely in and around the extremely hazardous construction environment. In addition, it was imperative to maintain diligent communication with Amtrak personnel and to develop a collaborative working relationship in order to facilitate the frequent track outages required during weekends and off hours.

Acute attention was paid to the varied contaminates that were required to be disposed of during construction. An organized method was developed to properly plan to handle, manage and dispose of those materials to different disposal facilities, minimizing the impact to the work areas and project schedule. A custom-made containment system was employed, helping to minimize disruption of the busy rail line. Additional caissons were added to improve foundation efficiency. The project is expected to be completed in February 2009.

Posillico has been installing foundation support systems for nearly 40 years. Starting with innovative vibration hammer techniques in 1970, the company continually has put a high level of importance on obtaining, understanding and perfecting the latest technologies. In the past few years, Posillico has expanded its operations to include a wide range of services related to subsurface foundation and retention systems.

National Slurry School

ADSC, the International Association of Foundation Drilling, presents its 9th National Slurry School Nov. 9-11, in Saint Petersburg, Fla. This educational opportunity is designed for personnel that are involved in the construction, design and inspection of drilled shaft foundations. Slurry drilled foundations are a practical and economical method of construction. When performed correctly, this procedure provides excellent results. This course will provide insights and practical information about the theory, chemistry and technology of constructing foundations using the slurry method of drilling. Useful information will be presented on the history and development of slurry drilling, and the principal advantages of various types of slurry materials, construction techniques and testing. This informative class is for ADSC members only, and the course fee is $1,095. Complete details and a registration form can be found at www.adsc-iafd.com.

Golf Outing Fundraiser

The Deep Foundations Institute Educational Trust and the ACE Mentor Program are putting on a golf tournament fundraiser at the Castlewood Country Club in Pleasanton, Calif., on Monday, Oct. 27. This is a great opportunity to network while enjoying one of California's premier golf courses, and, at the same time, benefiting the future of the industry. Get all the details at www.dfi.org.

On the Job

Case Meets
Piling Challenge

An addition to the A.S. King Power Plant in Stillwater, Minn., was made possible through the effort and expertise of Case Foundation Co., headquartered in Roselle, Ill.

The augered cast-in-place piling technique was used to install deep foundations 20 feet into weathered sandstone. The project involved the upgrading of the air-quality control system for the 560-megawatt coal-fired power plant. The site subsurface consisted of 20 feet of overburden overlying weak sandstone. The overburden consisted of sands and gravels with cobbles and boulders, and variable thicknesses of peat. Ground water at the site was approximately 8 feet deep. Two-foot-diameter piers were selected to facilitate installation through the cobbles and boulders in the overburden, and to penetrate the sandstone 22 feet. A total of 750 piers were installed.

During installation of the first pier, the weak sandstone broke down to sand-sized material that could not be cleaned from the pier hole without the use of slurry to hold the material in suspension. However, the use of slurry would significantly impact both schedule and cost. Since the sandstone could easily be drilled with the pier equipment, it was believed that 2-foot-diameter deep foundations could be installed as designed using augered cast-in-place piling techniques. A brief test-drilling program was conducted to evaluate the viability of 2-foot-diameter continuous-flight augers penetrating 22 feet into the weak sandstone. The test drilling indicated that augered cast-in-place installation techniques should be successful. Following a short delay to mobilize the additional required equipment, construction commenced. Installation of the 2-foot-diameter augered cast-in-place piling to a depth of 22 feet into the weak sandstone was successfully performed.

Founded in Chicago more than 50 years ago, Case Foundation Co. has evolved from a local drilled shaft contractor into a widely respected and successful full-service deep foundation specialist. Since its inception, Case has consistently led the way in deep foundation technology, from the introduction of mechanized drilled shaft construction, to the development of specialized tools for rock-socketed shaft installation, to the advancement of top-down concrete slurry wall construction.

Featured Product

CFA Drill Rig

The EM800SC drill rig, manufactured by CZM Foundation Equipment, is mounted on a hydraulic excavator chassis with its weight around of 20 tons for continuous-flight auger drilling applications. It uses the exclusive "Bottom Drive CFA" system, internationally patented by CZM. This version does not require the hydraulic extended crawlers of the excavator chassis. In this system, the drilling auger crosses the rotary head and takes part in the torque transmission mechanism, allowing the rotary head to be placed at the drill mast base. For more information, visit www.czm.com.br.

Check out Site Prep, a sister publication of The Foundations Report. Site Prep focuses on the challenges and opportunities of site preparation, including site clearing, earth moving, utilities and environmental activities. Go to www.siteprepmag.com, where you can subscribe to the magazine as well as its monthly newsletter, Industry Dirt.