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CASE G11 - Failure of Timber Pile Foundation, NRL, M. Yachnis, & J. V. Tyrrell
Problem:  Distress in structure, failure of timber pile foundation at Bldg. 43,
Naval Research Laboratory.
Symptoms:  Gradually diagonal shear cracks and tension cracks developed in
reinforced concrete beams and horizontal tension cracks in columns.  Differential
settlement became evident.
Collection of Facts:  Observation of the cracks indicated that the cracks on the
beams were generated by reversal of stress - Fig. 1.  The cracks in columns were
caused by lack of pile support which resulted in the adjacent framing supporting
the column instead of the column supporting the structure with the lower column and
pile caps creating a tension load - Fig. 2.
Exploratory pits were opened to check the timber piles and concrete pile caps. The
timber piles under the structural members which had experienced cracks were found
deteriorated and in some cases the upper portion was completely decayed. After an
extensive exploration at various locations of the piles, the problem area was
isolated.  A large diameter sewer pipe runs along the deteriorated piles. The
leakage from and infiltration  to the pipe was the apparent cause of the
Fig. 2
Fig. 1
Solution:  Possible causes of reinforced concrete beam and column cracking are
overloading, underdesign, material deterioration and poor quality of materials. In
addition, such in the above case, investigators should check for foundation
settlement, pile deterioration and failure in caps.

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