455-5.7 Water Jets: Use jet pumps, supply lines, and jet pipes that provide adequate
pressure and volume of water to freely erode the soil. Do not perform jetting without prior
approval by the Engineer or unless allowed by the Plans.
Do not perform jetting in the embankment or for end bents. Where conditions
warrant, with approval by the Engineer, perform jetting on the holes first, place the pile therein,
then drive the pile to secure the last few feet of penetration. Only use one jet for prejetting or
jetting through piles constructed with a center jet-hole. Use two jets when using external jets.
When jetting and driving, position the jets slightly behind the advancing pile tip (approximately
3 feet or as approved by the Engineer). When using water jets in the driving, determine the pile
bearing only from the results of driving after withdrawing the jets, except where using jets to
continuously eliminate soil resistance through the scour zone, ensure that they remain in place as
directed by the Engineer and operating during pile bearing determination. Where practical,
perform jetting on all piles in a pile group before driving begins. When large pile groups or pile
spacing and batter make this impractical, or when the Plans specify a jet-drive sequence, set
check a sufficient number of previously driven piles in a pile group to confirm their capacity
after completing all jetting.
455-5.8 Penetration Requirements: Measure the penetration of piles from the elevation
of natural ground, scour elevation shown in the Plans, or the bottom of excavation, whichever is
lower. When the Contract Documents show a minimum pile tip elevation or a minimum depth of
penetration, drive the tip of the pile to this minimum elevation or this minimum penetration
depth. In all such cases, the Engineer will accept the bearing of a pile only if the Contractor
achieves the required bearing when the tip of the pile is at or below the specified minimum tip
elevation or depth of penetration and below the bottom of the preformed or predrilled pile hole.
When the Plans do not show a minimum depth of penetration, scour elevation, or
minimum tip elevation, ensure that the required penetration is at least 10 feet into firm bearing
material or at least 20 feet into soft material unless otherwise permitted by the Engineer. If a
scour elevation is shown in the Plans, achieve these penetrations below the scour elevation. The
Engineer may accept a penetration between 15 feet and 20 feet when there is an accumulation of
five consecutive feet or more of firm bearing material. Firm bearing material is any material
offering a driving resistance greater than or equal to 30 tons per square foot of gross pile area as
determined by the Dynamic Load Testing (455-5.11.4). Soft material is any material offering less
than these resistances. The gross pile area is the actual pile tip cross-sectional area for solid
concrete piles, the product of the width and depth for H piles, and the area within the outside
perimeter for pipe piles and voided concrete piles.
Do not drive piles beyond practical refusal. To meet the requirements in this
Subarticle, provide penetration aids, such as jetting or preformed pile holes, when piles cannot be
driven to the required penetration without reaching practical refusal.
If the Contractor encounters unforeseeable, isolated obstructions that the
Contractor cannot practically penetrate by driving, jetting, or preformed pile holes, and the
Contractor must remove the pile to obtain the required pile penetration, the Department will pay
the costs for such removal as Unforeseeable Work.
455-5.9 Preformed Pile Holes:
455-5.9.1 Description: Preformed pile holes serve as a penetration aid when all
other pile installation methods fail to produce the desired penetration and when authorized by the
Engineer to minimize the effects of vibrations on adjacent structures. Preformed pile holes are
necessary when the presence of rock or strong strata of soils will not permit the installation of