Foundations Report 04-08 - HTML

Here is your complimentary issue of "The Foundations Report," an e-newsletter produced by your friends at National Driller magazine. Each month, we'll be sending you an update on the latest happenings in the foundation drilling industry. If you have anything you'd like to share with fellow foundation aficianados, kindly send along your news, announcements, photos, comments and anything else of interest to ettlingg@bnpmedia.com. And tell a friend. If you'd like to continue to receive "The Foundations Report," e-newsletter, just click here to automatically continue your free subscription.

Pile Driving Hammers

The good folks at the Pile Driving Contractors Association (PDCA) remind us that pile driving hammers shall be of the size needed to develop the energy required to drive the piles at a blow count that does not exceed 10 blows per inch at the required ultimate pile capacity. Some general guidelines from the PDCA's technical committee:

Drop hammers shall not be used for concrete piles or for piles whose required ultimate pile capacity exceeds 60 tons. When drop hammers are permitted, the ram shall have a weight not less than 1.0 ton, and the height of drop shall not exceed 12 feet. In no case shall the ram weight of drop hammers be less than the combined weight of the helmet and pile. All drop hammers shall be equipped with hammer guides and a helmet to ensure concentric impact.

Regarding air hammers, if a dynamic formula is used to establish the required blow count, the weight of the striking parts of air hammers used shall not be less than one-third the weight of pile and drive cap, and in no case shall the striking part have a weight less than 1.4 tons. If a wave equation analysis is used to establish the required blow count and driving stresses, this limitation on ram weight does not apply. The plant and equipment furnished for air hammers shall have sufficient capacity to maintain - under working conditions - the pressure at the hammer specified by the manufacturer. The hose connecting the compressor with the hammer shall be at least the minimum size recommended by the manufacturer. Hammer performance shall be evaluated at the end of driving by measuring blows per minute and comparing with the manufacturer's recommendations.

Some open-end diesel hammers are equipped with a device to measure impact velocity at all times during pile driving operations. If this device is not available, the stroke shall be obtained by measuring the speed of operation either manually or with a device that makes the measurement automatically. Closed-end diesel hammers shall be equipped with a bounce chamber pressure gauge in good working order, mounted near ground level so as to be easily read.

Hydraulic hammers shall be equipped with a system for measurement of ram energy. The system shall be in good working order, and the results shall be easily and immediately available.

Vibratory or other pile driving methods may be used only when specified in the contract documents or in writing. Except when pile lengths have been evaluated from load test piles, the ultimate pile capacity of piles driven with vibratory hammers shall be verified by redriving the first pile driven in each group of 10 piles with an impact hammer of suitable energy to measure the ultimate pile capacity before driving the remaining piles in the group.

You can check out PDCA's complete installation specifications for driven piles at www.piledrivers.org.

Brayman's Bridge
Replacement Project

Brayman Construction Corp., headquartered in Saxonburg, Pa., installed 176 total shafts for the foundation of the 40-span precast concrete segmental box girder bridge over the Susquehanna River Bridge in Harrisburg, Pa.

The $5.8 million project consisted of 156 shafts for the bridge piers with 72-inch rock sockets that averaged 15 feet in length, and 20 shafts for the bridge abutments with 42-inch rock sockets that averaged 10 feet in length. The rock sockets were installed in sandstones and siltstones with unconfined compressive strengths as high as 25 ksi. The project was particularly challenging, as 100 of the shafts for the piers were located within the limits of the Susquehanna River and its fluctuating water levels.

All shafts were inspected for cleanliness using a shaft inspection device to ensure that no more than one inch of debris or sediment was located on the shaft bottom. Cross-hole sonic logging (CSL) was performed to evaluate the presence of anomalies, defects or voids in the shaft concrete - and none were detected.

Incorporated in 1947 as a family business with a staff of two, Brayman has broadened its construction services from simple single-span box culverts to a become a $100 million nationally recognized provider of complex heavy/civil, demolition, geotechnical, marine, and steel erection construction capabilities. Brayman offer solutions to projects of all sizes and complexities in multiple public and private market sectors throughout the eastern United States.

Drilled Shaft Program

If you're interested in the latest in design and construction of drilled shafts, ADSC: The International Association of Foundation Drilling is presenting a drilled shaft seminar and exhibit program May 7-8, at the Sheraton Grand Hotel in Irving, Texas.

Drilled shafts have become the deep foundation of choice for many projects in the commercial and transportation industries. This seminar will provide the very latest information available, offering an entire spectrum of drilled shaft design, specifications, quality assurance/quality control testing, and recommended construction procedures.

To register, or for further details, you can visit www.adsc-iafd.com, or telephone 214-343-2091.

On the Job

Large-diameter
Caisson Project

The recent expansion of the John Jay College in Manhattan required the installation of more than 100 large-diameter caissons. What made the drilling of the caissons complex was the fact that the rock into which the caissons were socketed was serpentine, which is rock that has naturally occurring asbestos. In addition to the serpentine rock was the fact that there were two existing Amtrak railroad lines that ran through the site, and three of the caissons needed to be installed within the Amtrak right-of-way.

Posillico Drilling Inc, headquartered in Farmingdale, N.Y., overcame the problems associated with drilling into the serpentine rock by utilizing a custom-made containment system to keep all airborne particles contained. The firm also utilized its staff geologist to devise a system to drill into the rock to minimize the asbestos from becoming airborne. Within the railroad right-of-way, a shielding system was employed to protect the track, and by working during outages on weekends and off-hours, disruption on the busy rail line was limited.