Good Driving Practice

CEMP-E

EI 02G001

01 July 1997

(a) A preliminary wave equation analysis should be made as part of the foundation design

procedure to estimate driving stresses for the selected pile foundation, pile driving system, and cushions.

The pile can be expected to be overstressed and to be damaged if the driving energy of the selected

hammer is exceeded or thickness of pile cushions is reduced.

(b) Wave equation analysis will be performed as part of driving indicator piles with the PDA.

Results of this analysis will confirm the selection of the pile driving system and provide guidance on the

limits of the driving energy to be sure that driving stresses will be less than the allowable stresses.

(2) Good Driving Practice. All driven piles are subject to driving limitations.

(a) The piles will be properly aligned with the pile hammer and driving energy limited to

maintain driving stresses within allowable limits.

(b) Cushions will be maintained at the thickness determined from results of driving of indicator

piles with the PDA.

(c) Timber piles are especially vulnerable to brooming and splitting near the pile top or tip

when driven. Driving should stop immediately when hard driving is encountered as indicated by a sudden

increase in the penetration resistance or if the pile is observed to drift off location. A vibratory driver can be

substituted for an impact hammer to eliminate damage from hard driving.

(d) The driveability of concrete piles is often limited by the tensile strength of the pile,

especially long prestressed concrete piles. Concrete piles should be driven initially with low energy that is

about 50 percent of the maximum energy to be applied to the pile. The maximum driving energy is applied

when the pile is nearly at the embedment depth. This guidance therefore requires that concrete piles

should be driven with hammers of variable energy to safeguard the integrity of the pile.

(e) Steel piles, especially open-end pipe and H-piles, are capable of hard driving. Pile tips

may be protected with driving shoes, but prolonged hard driving should be avoided.

(f) Piles suspected of being damaged should be extracted and replaced. Vibratory drivers are

efficient extractors of piles if the pile can be clamped to the driver.

(g) Pile driving should cease immediately when sudden increases in penetration resistance are

observed to avoid overdriving. Timber piles are especially vulnerable to brooming or splitting at the top or

tip of the pile when hard driving occurs. Prolonged hard driving will be avoided.

(3) Restrike of Selected Piles. Selected piles will be restruck with PDA equipment to measure the

quality of the driven piles and to assess pile capacity.

(a) Piles that should be restruck include those that have some sign of possible malfunction,

but not judged serious enough to extract. Examples include penetration resistance that is not as high as

expected and where the pile capacity is in doubt, unexplained changes in penetration resistance,

penetration resistance not as high as previously driven piles, and piles with some damage at the pile head.

(b) Driving stresses evaluated by the analysis during restrike will not exceed the yield or

ultimate strength of the pile material. This provides a slight margin of safety against damage because the

duration of the peak of the driving stresses is short.

(c) The quality of restruck piles will be evaluated by the PDA technician and made a part of the

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