D7Now - How It's Made: Drilled Shaft Installation

did you ever wonder what supported those

big roadway signs masked arms and

straight holes this video will highlight

some inspection points and show how

miscellaneous drilled shaft foundations

are constructed you are watching d 7 now

how it's made references in this video

are based on the 2015 f DOD

specifications you must use the

applicable specifications for your

contract installation of all drilled

shafts must be inspected by CT QP

qualified drill shaft inspector a

drilled shaft inspector computer-based

training is available on the

Department's website inspectors should

familiarize themselves with the contract

documents including the plans design

standards and any applicable

specifications inspectors should also

review the approved drill shaft

installation plan shop drawings or

details and the drilled shaft inspectors

checklist inspect the contractors

equipment when it arrives on the

projects the types and sizes of the

equipment will be listed on the

contractors drill shaft installation

plan verify that the reinforcing cage is

assembled according to the plans

standard index or specifications for the

proper dimensions length spacing and

number of steel CSL tubes and spacers

and record this information on the drill

shaft reinforcement spacers law ensure

that all intersections of steel are tied

for miscellaneous shafts if the cleaning

operations result in excavating below

the required tip elevation the

reinforcing cage does not need to be

extended see specification 455 - 16

for information on reinforcing steel

construction and placement once the

location of the shaft is surveyed the

contractor will hand dig down the first

four feet of the shaft in order to

confirm there are no utility conflicts

in the shaft location install a

temporary surface casing from at least

one foot above the ground surface to at

least 5 feet below the ground surface

for miscellaneous structures fill the

excavation with pre-mixed mineral slurry

meeting the requirements of 455 - 15

point 8.1 or polymer slurry meeting the

requirements of 455 - 15 point eight

point two

before the drill advances to the bottom

of the temporary casing do not attempt

to excavate the shaft using the dry

construction method unless specifically

indicated in the plans as the contractor

begins to excavate record the death

times of when the auger is inserted and

extracted from the shaft and soul

descriptions on the drill shaft log

depth checks should be taken from a

known reference at elevation when the

shaft is excavated to the proposed tip

elevation the contractor will then use a

clean-out bucket to remove any sediment

deposits or other debris from the bottom

of the shaft perform a sounding of the

shaft bottom and record the depth and

amount of sediment on the drill shaft

law for miscellaneous shafts insured the

amount of sediment does not exceed one

inch over the bottom of the shaft sample

and test the slurry in the shaft to

ensure it meets the required properties

at the time of concrete placement for

specification 455 - 15 point 8 and

record the results on the drilled shaft

slurry testing log lower the reinforcing

cage into the shaft and secure to

prevent from settling or rising during

concrete placement

inspect the CSL tubes to ensure the

serviceability and fill the tubes with

clean potable water and recap prior to

concrete lower the sealed watertight

tremie or pump line into the shaft and

ensure that the discharge end is within

six inches of the bottom of the shaft

excavation until at least 10 feet of

concrete has been placed support the

trim ease so that it could be raised or

lowered to increase or reduce the

discharge of concrete

do not rapidly raise or lower the

trimming to increase discharge of

concrete determine the theoretical

volume concrete needed in the shaft and

used the drilled shaft concrete

placement log and the drilled shaft

concrete volumes log when the concrete

truck arrives to the project check the

DLC ticket for approved mix design water

cement ratio mixing revolutions and

batch times sample and perform the

required plastic properties tests place

concrete as soon as possible after

completing all excavation cleaning

inspecting the shaft bottom and

immediately after placing reinforcing

steel maintain a minimum slump of 5

inches throughout the elapsed time which

includes the concrete mix and in transit

time the concrete placement time the

time required to remove the temporary

casing and the time to insert any

required column steel bolts weldments

etc measure and record the depth to the

top of the concrete after each load and

record the depth on the drilled shaft

concrete placement log continued placing

concrete after the casing is full until

good quality concrete is evident at the

top of the casing after the shaft is

over poured sufficiently to eliminate

all contaminated concrete additional

concrete may be added to the shaft

without the use of a trimming or pump in

accordance with section 401 Stu concrete

has been over poured removed the

trimming or pump line and the temporary

surface casing install the conduit set

the top form to the proposed shaft top

elevation and install the anchor bolts

use the drilled shaft concrete volumes

log to plot the actual concrete curve

and compare it to the theoretical the

volume curve is important because it

allows you to see if there are any

potential issues with the shaft

cure the top surface of the shaft in

accordance with the applicable

provisions of section 402 contractor may

remove the forms prior to seven days

provided that concrete strength has

reached 2,500 psi or greater as

evidenced by cylinder breaks ensure that

all construction tolerance are met for

specification 455 - 20