CASE G2 - Failure of Concrete Caissons, M. Yachnis
Problem: Failure of concrete caissons and difficulties during caisson
placements due to existence of underground obstructions at the Naval Regional
Medical Center, Bethesda, Maryland.
Symptoms: During placements of concrete caissons to be used as foundation of
the new replacement of the hospital facilities, distress of caissons was
observed due to unexpected underground obstructions. Based on the soil
borings, geotechnical consultants could not provide a reasonable explanation
of the difficulties encountered during the driving of the caissons.
Collection of Facts: A number of caissons was retrieved from the ground and
carefully observed. It became obvious that the driving was performed through
hard material equivalent to solid rock. It was recommended that a test pit be
opened to visually examine the sub-soil conditions. Large utility, sewer, and
water lines, and electrical conduits were uncovered which were the cause of
the problem. The unexpected extensive obstacles resulted in considerable time
delays and very expensive change orders.
Solution: It is imperative to map all existing utilities-water, sewer, and
electrical-which must be included in the bid-package.
CASE G3 - POL (Petro-Oil-Lubricants) Facility at Naval Air Station,
Sigonella, Sicily, M. Yachnis
Failure of the steel plate at the bottom of three 4500 barrel fuel
Symptoms: Upon completion of the project and before filling with fuel, the
steel bottom plates buckled and warped (See Fig. 1). Cracking also occurred
in several areas of the steel plates.