The construction site for the project will be a multi-story commercial dwelling with deep basement car park located in city centre at Smithfield where there is a high level of water content as it is in close proximity to the river Liffey, lack of space due to other buildings, traffic level are high and one way system is the only option. The design team have proposed ‘type C drained cavity’ basement that will consist of ‘secant piling system that has to be delivered in accordance with the project schedule.

1. DEPARTMENT OF CONSTRUCTION MANAGEMENT
PROJECT COVER SHEET
STUDENT NAME: DC
STUDENT NUMBER: C 123
COURSE/ YEAR DT117/4
SUBJECT: Advanced Construction
Technology
PROJECT TITLE: Deep Basement Excavation
LECTURER:
FOR OFFICE USE ONLY:
DATE DUE: 10th
February 2016
DATE RECEIVED:
RECEIVED BY:
REPEAT PROJECT?
MARKS:

2. Introduction
The construction site for the prophase of the project will be a multi-story commercial dwelling with
deep basement carpark located in city centre at Smithfield where there is a high level of water content
as it is in close proximity to the river Liffey, lack of space due to other buildings, traffic level are high
and one way system is the only option. The design team have proposed ‘type C drained cavity’ basement
that will consist of ‘secant piling system that has to be delivered in accordance with the project schedule.
Project management has to plan for the following in relation to deep basement construction:
The first thing a CM will do is find out the ground conditions/cut-off points on the Smithfield project
determining the water levels below ground and depth of the required excavation. Also problems that
may be incurred during a city centre project are existing underground services such as water mains and
drainage. Cat-scan will be carried out to locate these services that will allow for additional measures
that may be necessary such as diversion of services. (DEEPEX, 2015)
Specific management plans
All basement projects are to include traffic management plan regards to impact on traffic surrounding
the site showing the impact for the construction schedule and surrounding services such as ambulances,
buses etc. and demolition management plan (CDMP) showing materials handling and storage,
establishment of welfare facilities for the workers on the site a clear construction sequence illustrated
with sketches and detailed diversion of working swears. (personal.cityu)
Project Scheduling
As time equals money quality of planning and scheduling of highly efficient working programme will
be vital for success of a safe on time project without any disturbances to works that may set back the
project to the completion date or require more resources that were not planned for. The project will
require layout and planning of the site accommodation and phasing/sectioning of the job. (teckrackher,
n.d.)
Associated risk and safety
(ADSC, 2015) Health and safety plan will have to be made stating the nature of the work, method
statement of the project, and risks associated with the project. Potential unforeseeable problems during
the construction process of deep basement construction are:
1. The effect of water ingress or pressure on the stability of bored pile walls and excavations
2. Collapse or failure of excavation walls
3. Disturbance of adjoining buildings and structures
Such risks will have to be eliminated by putting in place corrective measures such as:
1. To eliminate the effect of water egress predictability of conditions during the construction
period will be made. Temporary pumping and measures to prevent flooding will be installed.
Monitoring of water levels during construction period to predict potential risk.
2. To prevent the collapse of the basement wall anchors and tiebacks will be used to retain the
wall in place. Available expertise skill will be needed to calculate the vertical loads and lateral
loads to determine if the piles will be able to carry out their function additional shoring can be
placed against the excavated piles.
3. Disturbance to adjoining buildings can be eliminated through public relations and minimization
of the noise control during specified hours. Sprinkler systems will be used to eliminate
construction debris. (ADSC, 2015)

3. Introduction to Secant piles
The following section will focus on the construction methods used to
deliver Secant pile deep basement from site management perspective.
Secant pile walls are formed by drilling intersecting (one pile with
another) reinforced concrete piles. The research shows that secant
piles are reinforced with either steel rebar or with steel beams.
Primary (female) piles are installed first with secondary (male) piles
constructed in between primary (female) piles once the concrete
gains sufficient strength. Pile overlap is typically in the order of 8 cm
and can go in depths of up to 45 meters. (Baxter, 2012)
Construction procedures of secant pile wall
The secant pile wall will be set out with the piles distances centre-to-centre spacing and is drilled in two
stages. 1st
stage involves drilling and placing of primary piles and 2nd
stage will involve drilling the
secondary piles in-between the primary wall. (Concrete-group, 2016)
 The guide wall will be excavated which is a precast concrete wall to secure the wall alignment
but is not necessary.
 The male piles are bored through the female piles before the concrete has achieved its full
strength.
 Once the Rebar is placed and poured the levelling of the excavation can begin. First the guide
wall is removed.
 Once the wall is excavated to a depth of 2 meters ground anchors may be used.
Ground anchors
Ground anchors are used for installation that is capable of
transmitting an applied tensile load to a load bearing
section which may be a soil or rock to provide resistance to
structural movements. The advantage of ground anchors is
that excavation can stay unobstructed. The ground anchors
will be installed at an angle in the concrete pile. The hole
will be bored where the rebar will be placed and then
injected with concrete. The end of the anchor will be cut
and a cap put on top. (Ergun, 2008)
Ground water barriers
To achieve a water tightens it will be necessary for the CM
to build a skin wall to the sides of the piles. First step is by
cleaning the piles from any remaining spoil. Next shotcrete
will be pumped to the wall. Then waterproof membrane will
be placed on the wall by screwed to the main structure of
the wall. Once the membrane will be on polyethylene
studded sheets will be overlapped to seal the secant pile
wall. Then reinforced concrete levelled walls will be made
to cover the drainage system where it will be poured over
drainage pipe located 20cm from the wall. 50mm concrete
blinding will provide clean working surface for positioning
the mesh floor slab so the concrete can be poured pour.

4. Advantages of using secant piles
The main advantages of secant pile walls are:
1. Increased wall stiffness compared to sheet piles.
2. Can be installed in difficult ground.
3. Used in high water table conditions.
4. Columns can be as close as 5m from existing
buildings. (Wong, 2002)
The main disadvantages of secant pile walls are:
1. Verticality tolerances may be hard to achieve
for deep piles.
2. Total waterproofing is very difficult to obtain in
joints.
3. Increased cost compared to sheet pile.