1810.4 - Installation
Deep foundations shall be installed in accordance with Section 1810.4. Where a single deep foundation element comprises two or more sections of different materials or different types spliced together, each section shall satisfy the applicable conditions of installation.
1810.4.1
Structural integrity.
Deep foundation elements shall be installed in such a manner and
sequence as to prevent distortion or damage that may adversely affect the
structural integrity of adjacent structures or of foundation elements being
installed or already in place and as to avoid compacting the surrounding soil
to the extent that other foundation elements cannot be installed properly.
1810.4.1.1
Compressive strength of
precast concrete piles. A precast concrete pile shall not be driven
before the concrete has attained a compressive strength of at least 75 percent
of the specified compressive strength (f
c), but not less than the strength sufficient
to withstand handling and driving forces.
1810.4.1.2
Casing. Where
cast-in-place deep foundation elements are formed through unstable soils and
concrete is placed in an open-drilled hole, a casing shall be inserted in the
hole prior to placing the concrete. Where the casing is withdrawn during
concreting, the level of concrete shall be maintained above the bottom of the
casing at a sufficient height to offset any hydrostatic or lateral soil
pressure. Driven casings shall be mandrel driven their full length in contact
with the surrounding soil.
1810.4.1.3
Driving near uncased
concrete. Deep foundation elements shall not be driven within six
element diameters center to center in granular soils or within one-half the
element length in cohesive soils of an uncased element filled with concrete
less than 48 hours old unless approved by the building
official. If the concrete surface in any completed element rises or
drops, the element shall be replaced. Driven uncased deep foundation elements
shall not be installed in soils that could cause heave.
1810.4.1.4
Driving near cased
concrete. Deep foundation elements shall not be driven within four and
one-half average diameters of a cased element filled with concrete less than 24
hours old unless approved by the building
official. Concrete shall not be placed in casings within heave range
of driving.
1810.4.1.5
Defective timber piles. Any substantial sudden increase in rate of
penetration of a timber pile shall be investigated for possible damage. If the
sudden increase in rate of penetration cannot be correlated to soil strata, the
pile shall be removed for inspection or rejected.
1810.4.2
Identification. Deep
foundation materials shall be identified for conformity to the specified grade
with this identity maintained continuously from the point of manufacture to the
point of installation or shall be tested by an approved
agency to determine conformity to the specified grade. The
approved
agency shall furnish an affidavit of
compliance to the building official.
1810.4.3
Location plan. A plan
showing the location and designation of deep foundation elements by an
identification system shall be filed with the building
official prior to installation of such elements. Detailed records for
elements shall bear an identification corresponding to that shown on the
plan.
1810.4.4
Preexcavation. The use of jetting, augering or other methods of
preexcavation shall be subject to the approval of the building
official. Where permitted, preexcavation shall be carried out in the
same manner as used for deep foundation elements subject to load tests and in
such a manner that will not impair the carrying capacity of the elements
already in place or damage adjacent structures. Element tips shall be driven
below the preexcavated depth until the required resistance or penetration is
obtained.
1810.4.5
Vibratory
driving. Vibratory drivers shall only be used to install deep foundation
elements where the element load capacity is verified by load tests in
accordance with Section 1810.3.3.1.2. The installation of production elements
shall be controlled according to power consumption, rate of penetration or
other approved means that ensure element capacities equal or
exceed those of the test elements.
1810.4.6
Heaved elements. Deep
foundation elements that have heaved during the driving of adjacent elements
shall be redriven as necessary to develop the required capacity and
penetration, or the capacity of the element shall be verified by load tests in
accordance with Section 1810.3.3.1.2.
1810.4.7
Enlarged base cast-in-place
elements. Enlarged bases for cast-in-place deep foundation elements
formed by compacting concrete or by driving a precast base shall be formed in
or driven into granular soils. Such elements shall be constructed in the same
manner as successful prototype test elements driven for the project. Shafts
extending through peat or other organic soil shall be encased in a permanent
steel casing. Where a cased shaft is used, the shaft shall be adequately
reinforced to resist column action or the annular space around the shaft shall
be filled sufficiently to reestablish lateral support by the soil. Where heave
occurs, the element shall be replaced unless it is demonstrated that the
element is undamaged and capable of carrying twice its design load.
1810.4.8
Hollow-stem augered,
cast-in-place elements. Where concrete or grout is placed by pumping
through a hollow-stem auger, the auger shall be permitted to rotate in a
clockwise direction during withdrawal. As the auger is withdrawn at a steady
rate or in increments not to exceed 1 foot (305 mm), concreting or grouting
pumping pressures shall be measured and maintained high enough at all times to
offset hydrostatic and lateral earth pressures. Concrete or grout volumes shall
be measured to ensure that the volume of concrete or grout placed in each
element is equal to or greater than the theoretical volume of the hole created
by the auger. Where the installation process of any element is interrupted or a
loss of concreting or grouting pressure occurs, the element shall be redrilled
to 5 feet (1524 mm) below the elevation of the tip of the auger when the
installation was interrupted or concrete or grout pressure was lost and
reformed. Augered cast-in-place elements shall not be installed within six
diameters center to center of an element filled with concrete or grout less
than 12 hours old, unless approved by the building
official. If the concrete or grout level in any completed element
drops due to installation of an adjacent element, the element shall be
replaced.
1810.4.9
Socketed
drilled shafts. The rock socket and pipe or tube casing of socketed
drilled shafts shall be thoroughly cleaned of foreign materials before filling
with concrete. Steel cores shall be bedded in cement grout at the base of the
rock socket.
1810.4.10
Micropiles. Micropile deep foundation elements shall be permitted to be
formed in holes advanced by rotary or percussive drilling methods, with or
without casing. The elements shall be grouted with a fluid cement grout. The
grout shall be pumped through a tremie pipe extending to the bottom of the
element until grout of suitable quality returns at the top of the element. The
following requirements apply to specific installation methods:
1. For micropiles grouted inside a temporary
casing, the reinforcing bars shall be inserted prior to withdrawal of the
casing. The casing shall be withdrawn in a controlled manner with the grout
level maintained at the top of the element to ensure that the grout completely
fills the drill hole. During withdrawal of the casing, the grout level inside
the casing shall be monitored to verify that the flow of grout inside the
casing is not obstructed.
2. For a
micropile or portion thereof grouted in an open drill hole in soil without
temporary casing, the minimum design diameter of the drill hole shall be
verified by a suitable device during grouting.
3. For micropiles designed for end bearing, a
suitable means shall be employed to verify that the bearing surface is properly
cleaned prior to grouting.
4.
Subsequent micropiles shall not be drilled near elements that have been grouted
until the grout has had sufficient time to harden.
5. Micropiles shall be grouted as soon as
possible after drilling is completed.
6. For micropiles designed with a full-length
casing, the casing shall be pulled back to the top of the bond zone and
reinserted or some other suitable means employed to assure grout coverage
outside the casing.
1810.4.11
Helical piles. Helical
piles shall be installed to specified embedment depth and torsional resistance
criteria as determined by a registered design professional.
The torque applied during installation shall not exceed the maximum allowable
installation torque of the helical pile.
1810.4.12
Special inspection.
Special inspections in accordance with Sections 1704.8
and 1704.9 shall be provided for driven and cast-in-place deep foundation
elements, respectively. Special inspections in accordance with
Section 1704.10 shall be provided for helical piles.
Notes
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