Article 9 - PILE DRIVING OPERATIONS

Section 27-703

Section 27-703

  §  27-703  Exceptions. The provisions of sections 27-704 and 27-705 of
this article shall not apply to piles driven with a vibratory hammer  or
other equipment wherein the energy of impact cannot be evaluated.

Section 27-704

Section 27-704

  § 27-704 Equipment. (a) General. The hammer shall travel freely in the
leads.  The  cushion  or  cap  block  shall be replaced, if crushed. The
hammer shall deliver its rated energy, and measurements shall be made of
the fall of the  ram  or  other  suitable  data  shall  be  observed  at
intervals  as  required  to  verify  the  actual energy delivered at the
termination of driving.
  (b) Cushion or cap block. The cushion or cap block shall  be  a  solid
block  of  hardwood with its grains parallel to the axis of the pile and
enclosed in a tight-fitting steel housing, or  shall  be  an  equivalent
assemblage.  If  laminated materials are used, the type and construction
of these materials shall be such that their strength  is  equal  to,  or
greater  than,  hardwood. Wood chips, pieces of rope, hose, shavings, or
automobile tires and similar materials shall not  be  used.  Cap  blocks
shall be replaced if burned, crushed, or otherwise damaged.
  (c) Followers. Followers shall not be used unless permitted in writing
by the architect or engineer, and only when necessary to accomplish such
installation.  They  shall  be of steel or hardwood of such size, shape,
length, and weight as to permit driving the pile in the desired location
and  to  the  required  depth  and  resistance.  The  required   driving
resistance  tabulated  in  Tables  11-4  and  11-5 shall be increased to
compensate for the loss of energy in the hammer blow. The follower shall
be a single length section, shall be provided  with  a  socket  or  hood
carefully  fitted  to the top of the pile to minimize loss of energy and
to prevent damage to the pile, and shall  have  sufficient  rigidity  to
prevent "whip" during driving.

Section 27-705

Section 27-705

  §   27-705  Procedures.  (a)  Continuous  Driving.  Driving  of  piles
preliminary to  final  seating  shall  be  continuous  for  an  interval
adequate to break or prevent the development of freeze. The hammer shall
be operated at its rated speed during this interval.
  (b)  Jetting.  Jetting,  augering  and other methods of pre-excavation
shall not be used unless  permitted  in  writing  by  the  architect  or
engineer.    When  permitted,  such procedures shall be carried out in a
manner which will not impair the carrying capacity of the piles  already
in  place  or  the  safety  of  existing adjacent structures. Jetting or
augering shall be stopped at least three feet above the  final  expected
pile-tip  elevation  and  at least three feet above the tip elevation of
any pile previously driven within six feet of the jet or  auger,  except
that  where  piles  are to be end bearing on rock or hardpan, jetting or
augering may be carried to the surface of the  rock  or  hardpan.  Piles
shall  be  carried  down  beyond the depth of jetting, augering or other
pre-excavation until the required resistance is obtained.  If  there  is
evidence   that   jetting   or   other  procedures  have  disturbed  the
load-bearing capacities of previously installed piles, those piles  that
have  been  disturbed  shall  be  restored  to  conditions  meeting  the
requirements of this article by redriving or by other methods acceptable
to the architect or engineer.   Redriving  or  other  remedial  measures
shall  be  instituted  after the jetting or other operations in the area
have been completed.
  (c) Sequence of installation. Individual piles and pile  groups  shall
be  installed  in  such  sequence  that:  (1)  the  carrying capacity of
previously installed piles is not reduced; (2) the soil surrounding  the
piles  is  not  compacted  to  the  extent that other piles in the group
cannot be installed properly; and (3) ground movement that would  damage
adjacent  buildings or utilities is prevented. In general, in any group,
driving shall start from one side and proceed progressively  toward  the
other  side  of  the  group  or  shall start from the middle and proceed
toward the edges of the group.
  (d) Heaved piles. In soils in which the installation of  piles  causes
previously  installed  piles to heave, accurate level marks shall be put
on all piles immediately after installation, and  all  piles  that  have
been  heaved  by  an amount in excess of one-quarter of an inch shall be
redriven to the required resistance.
  (e) Penetration measurements. Penetration measurements  made  for  the
purpose of determining resistance to driving shall not be made when pile
heads are damaged to an extent that may affect measured penetration, nor
shall  they  be  made  immediately  after fresh cushion blocks have been
inserted under the striking part of the hammer.