Drilled Shafts - Verification of Design.

Drilled shafts should be constructed adequately and certified by the  inspector.  Large shafts supporting major structures are sometimes  tested to ensure compliance with plans and specifications.   Sonic techniques may be used to ascertain homogeneity of the foundation.  Sonic wave propagation with receiver embedded in the concrete is the most reliable method for detecting voids or other defects.  Striking a drilled shaft as ina
large  strain test with PDA and wave equation analysis is recommended for analysis of the ultimate pile capacity and load-displacement behavior as decribed above for driven piles.  A  large strain test may be conducted by dropping a heavy load onto the  head of the shaft using a crane.  Static load tests are commonly performed on selected shafts or test shafts of large construction projects to verify shaft performance and efficiency of the design.

a.   Performance control.  Continuous monitoring is essential to ensure that the boreholes are properly prepared to minimize loss of soil friction and end-bearing capacity and that the concrete mix is placed to achieve a continuous adequate shaft....

b.   Nondestructive tests. Nondestructive tests.  Routine inspection with nondestructive  tests (NDT) using wave propagation shall be performed  to check the quality of the installed drilled shafts. Additional special tests as indicated in the following paragraphs are performed....

c.   Load  tests. The only positive way to prove the integrity  of a suspected drilled shaft is to perform a load test.  Drilled shafts are often constructed in relatively large sizes  and load tests are often not economically feasible. Replacing  a suspected drilled shaft is often more....

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