In urban environments, construction frequently must be undertaken near other structures with the result that the excavation for new construction must be vertical, and support or underpinning must be provided for adjacent shallow foundations and surface infrastructure. There are many ways to support temporary excavations, including anchored sheet pile walls and soldier beams with timber or concrete beam lagging. For tied-back sheet pile retaining walls, the piles are driven from the surface and the anchors are installed as the excavation proceeds. For soldier beam and lagging walls, vertical support members are installed from the surface and lagging is installed concurrent with the excavation. Other techniques include soil nail walls, soil-cement walls, and tangent caisson walls. D’Appolonia has experience with all types of construction techniques used for temporary excavation support and underpinning existing foundations to protect them from disturbance during excavation. Our experienced staff can select a suitable approach based upon technical requirements and construction costs and can prepare the required designs, plans and specifications. We routinely work with specialty contractors who perform this type of work and we normally provide monitoring services during construction.

D'Appolonia reviewed the design of this retaining wall as part of its work scope related to construction of the Pittsburgh Convention Center.

Descriptions of several D'Appolonia projects involving design of excavation support structures are provided in the following:


Geotechnical Engineering for Light Rail Transit System

D'Appolonia provided geotechical engineering consulting serices, prepared designs and provided construction management services for construction of a light rail transit system in Pittsburgh, Pennsylvania. The construction work included a subway requiring deep excavations in the central business district of Pittsburgh under two major streets with adjacent high-rise structures.

Excavation Support Systems for Saluda Dam Rehabilitation

D'Appolonia was retained by a specialty contractor to design temporary support structures associated with construction of a roller compacted concrete (RCC) dam near Columbia, South Carolina. The work included design of two anchored tie-back wall sections, anchoring for an existing concrete retaining wall, structures to support anchor blocks for circulating water lines, two cut-off walls, and two soil-nail walls.

Geotechnical Engineering for Floating Casinos

D'Appolonia was retained to provide geotechnical engineering consulting services related to construction of two floating entertainment complexes on the Mississippi River. The work included design of a two-tiered anchored soldier pile and lagging retaining wall system in loess soil deposits to allow for construciton of an access road. The work also included design of a retaining wall system to provide an enclosure to protecting a floating casino from river forces.

Effect of Subsurface Conditions on Diaphragm Wall Construction

D'Appolonia was retained by a specialty contractor constructing a deep excavation in Jersey City, New Jersey to provide consulting services relative to dealing with glacial till encountered in the excavation.

Concrete Diaphragm Cutoff Wall for Hotel Parking Garage

The Milwaukee Center project comprised construction of an office tower ranging in height from 16 to 30 stories. The project required 800 parking spaces, and the only available space for a parking garage was beneath the proposed construction footprint. In support of the foundation design, D'Appolonia conducted finite element analyses for evaluation of the required slurry wall thickness, permeability and depth, so that the pressure associated with the groundwater surrounding the excavation would not affect construction activities or long-term operation of the facility.

Braced Sheet-Pile Excavation Adjacent to the Ohio River

As part of an overall facility expansion plan, D’Appolonia prepared designs and technical specifications for the development of a waste water treatment plant at an integrated steel mill. D’Appolonia provided subsurface exploration and designs for various aspects of the plant including foundations, slope stabilization, anchored retaining walls and temporary excavation support.

Anchored Reinforced-Concrete Diaphragm Wall for Deep Excavation Support

D’Appolonia designed an anchored, reinforced-concrete (RC) diaphragm wall associated with the construction of a below-grade parking garage and hospital facility expansion at the Cambridge Hospital in Cambridge, Massachusetts. The reinforced-concrete diaphragm wall was designed to provide temporary excavation support, to serve as the permanent exterior wall of the parking garage, and to act as the foundation wall for a multi-story addition to the existing hospital.