Abstract:
The Pennsylvania Turnpike Commission has undergone significant expansion of its toll roads in Pennsylvania over the last 20 years, including 83+miles of new highways and 133+ miles of reconstructions and widenings. The geotechnical conditions have varied widely from karst in the east, to steeply dipping & fractured rock in mountains, and to landslide prone sedimentary rocks in the west. None of these complex conditions has really contributed to millions of dollars of claims by contractors in construction relating to failed support of excavation and resulting time delays.
In 2017 The Commission developed a new special provision for temporary shoring to make it more truly a design-build, performance based special provision, in an effort to best homogenize responsibilities and to avoid claims & delays.
The presentation will include:
1)Case histories of past failures and lessons learned.
2)Brief review of the special provision and two new, key elements: -Geotechnical Investigation: The contractor is required to interpret the subsurface conditions for themselves, by means of re-logging existing borings and/or performing new borings.
-Monitoring: Weekly survey of monitoring points, with action levels requiring stoppage of work.
3) Paradigm shifts on the owner, designer, and inspector side of the business:
-Prior to advertising, perform additional borings in areas of anticipated shoring, in order to provide the contractor with a reasonable basis for bids.
-Limit shoring design reviews to be primarily advisory comments only. The lawyers will say that "you have to let them fail."
-Deviation from the design in construction requires approval from the contractor’s engineer.
4)Case histories will be presented of successful projects since the changes. These included a shoring failure but the new process kept all parties responsible for their own work