Many years ago deep foundations meant driving multiple piles that were connected at the surface by a pile cap or grade beam to support design structural loads. Now other alternatives such as drilled shafts and micropiles are available and in many cases provide a more attractive and economical solution. Drilled shafts can be constructed large enough that caps may not be required and the construction does not cause the noise and vibration associated with driven piles. Micropiles (sometimes referred to as minipiles or pinpiles) are the fastest growing area of pile/drilled shaft construction. Micropile technology was developed in Europe in the 1950s and since the mid-1980s has gained worldwide acceptance. Micropiles are small-diameter shafts (typically less than 12 inches) and can extend to depths of up to 200 feet. Because of the small diameter, construction can be accomplished in small spaces. Micropiles can be used to replace large-diameter shafts, to underpin structures with limited access, and as in-situ reinforcements to stabilize slopes and excavations. D'Appolonia's experience includes all types of deep foundations. We have used micropiles to replace drilled shafts as part of value engineering studies with resultant cost savings, and we have used micropiles to stabilize a landslide that threatened a major highway.

ABOVE: Concrete placement using the
tremie method.

RIGHT: Reinforcing steel being lowered
into steel casing for caisson prior to
concrete placement.

Descriptions of D'Appolonia projects related to driven pile, drilled shaft and micropile foundations are provided in the following:


Consulting Services for Innovative Lock and Dam Replacement

D'Appolonia was responsible for design of drilled-shaft foundations, an under-base drainage system, and alignment mooring elements for the new Braddock Dam, which was constructed using innovative float-in construction technology. The work included evaluation of test results for the drilled-shaft load test.

Convention Center Geotechnical and Environmental Services

D’Appolonia developed recommendations for rock-socketed drilled shaft foundations for the Pittsburgh Convention Center. The drilled-shaft designs had to account for highly variable loading associated with an unusual design. D'Appolonia monitored construction of more than 450 drilled shafts and provided as-needed geotechnical and environmental consulting services throughout the project.

Value-Engineered Micropile Foundation Alternate

D’Appolonia teamed with a micropile contractor to perform a value-engineered foundation study for two of the five piers for the Gene Hartzell Memorial Bridge. Our design involved replacement of 48-inch-diameter drilled shafts with micropiles. D'Appolonia's designs were implemented by PennDOT resulting in savings of an estimated $200,000 and three months in construction time.

Blue Trail Landslide Stabilization on U.S. Route 26/89 in Wyoming

D’Appolonia developed a repair scheme incorporating a three-tiered configuration of reticulated micropile walls to stabilize a landslide that had been a major maintenance problem for the Wyoming DOT. For its work on the project, D'Appolonia was awarded the 1998 Grand Award for Excellence in Engineering Design by the American Consulting Engineers Council.

Geotechnical Engineering Services for Correctional Facility

D'Appolonia provided consulting geotechnical engineering services to Westmoreland County, Pennsylvania for the planning, design and construction of a $30 million correctional facility. The scope of work included design of drilled-shaft foundations and design of a 600-foot-long mechanically stabilized earth (MSE) retaining wall. We provided full-time construction monitoring services for the project.

Cost Savings through Alternate Foundation Design

D’Appolonia prepared alternate foundation recommendations for a $125 million chemical plant for a site located near the Mississippi River. Subsurface soils at the site consisted of relatively soft, compressible clay. D’Appolonia demonstrated that planned site tanks could be placed on less expensive ring foundations and that the original pile capacity predictions for process structure foundations could be increased. The alternative design led to a substantial cost savings and a reduction in construction time.