D'Appolonia has extensive experience in the design and construction of underground structures such as transit system tunnels, large-diameter sewage system conduits, tunnels and penstocks for hydroelectric power generation, and industrial plant intake and outlet conduits. Our experience includes field exploration programs to obtain soil and rock samples for laboratory testing and assessment of strength parameters. We have prepared designs for structures to resist potential internal and external forces and have also designed shoring systems and temporary support to maintain safe excavations during construction. We have also designed dewatering systems to allow construction in the dry.

Our experience includes design of hydraulic structures and equipment to move fluids through underground pipelines and tunnels. We routinely prepare plans and specifications associated with construction of facilities that we design and we typically provide monitoring services during construction.

Aerial view of shoring for downtown section of the Pittsburgh Light Rail Transit (LRT) system.

Some descriptions of D'Appolonia projects involving tunnels and underground construction are provided in the following:


Geotechnical Engineering for Light Rail Transit System

D’Appolonia provided geotechnical engineering consulting services, prepared designs and provided construction management services over a ten-year period for the construction of a light rail transit (LRT) system connecting metropolitan and south suburban Pittsburgh, Pennsylvania. The work included both above- and below-ground components of the system.

Redesign of Fossil-Fuel Power Plant Cooling Water Intake Canal

D’Appolonia developed designs to rehabilitate a cooling water intake canal at a 700-MW power plant. The selected remedial concept involved the construction of two buried 11-foot-diameter concrete pipes connecting new inlet and outlet transition structures. The work was completed on an expedited schedule to minimize outage at the power plant.

Ground Improvement for Coal Refuse Conveyor Tunnel Construction

D’Appolonia was retained to investigate an abandoned coal mine and to determine its possible effect on a tunnel to be constructed through the area. We developed a program of grout injection through 100-foot-deep boreholes to stabilize loose and/or unstable rock conditions. The grouting program successfully mitigated the poor tunnelling conditions and allowed the tunnel to be completed on schedule.

Evaluation of Spillway Tunnel for Hydropower Generation Usage

As part of a study to determine the feasibility of pressurizing a spillway outlet tunnel for hydropower generation, D’Appolonia planned and conducted an extensive in-situ testing program that included drilling and sampling of the tunnel liner and surrounding rock, hydraulic pressure testing, crack survey and evaluation of laboratory testing results.