Economical Basement Construction

The provided content discusses the construction of basements and the various methods used to achieve this. Raft foundations are used where the floor is not hard or where columns are spaced closely. The cost comparison of different basement construction methods shows that pad footing, strip footing, and open cut methods are relatively inexpensive, while sheet pile, diaphragm wall, and top-down methods are more expensive. The content also explains the step-by-step process of constructing a basement using the RCC poured walls method, including excavation, underpinning, and propping.

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Basement Construction
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Table of Contents
Executive summary....................................................................................................................2
Introduction................................................................................................................................3
Site analysis................................................................................................................................4
Suitability and buildability of the various basement construction methods in response to
specific site conditions...............................................................................................................5
Types of Basement.................................................................................................................5
Types of Basement foundations:..........................................................................................14
Cost comparison of the different type of basement construction methods..............................15
Construction sequencing illustration........................................................................................16
Conclusion................................................................................................................................18
References:...............................................................................................................................19

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Executive summary
A basement is a structural portion of a building that is either partially or completely below the
natural ground level. From a structural perspective of a common man, one may think that all
the basements are designed equal. But the reality is that each basement design has its own
pros and cons. They can be at different levels according to the requirement of the building
and the purpose of the basement to be used. In this office building, we need a basement for
the parking purpose. The construction of any type of basement is quite a difficult task and it
is also a high-risk work that can affect the existing structures of that area because we need to
dig under the ground which affects the water table and the soil. The architects and the
structured engineers work together to simplify this problem and deliver any project on time
with cost-effectiveness.

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Introduction
The Government of New South Wales has launched a program named Newcastle Urban
Transformation and Transport Program Transport for NSW (TFNSW) is the main public
transport agency of the Government of NSW. The main purpose of this policy is to give and
issues the policies regarding the all the models and kind of transportation that will help the
commoners to travel in the city. It also helps the local bodies to plan and construct the roads
to commute easily without any traffic-related infrastructure in NSW. The main reason why
we are doing this project and making a report about it is to present the necessary technical
information regarding the project like the construction of the building and the techniques to
be used for its construction. The main purpose of the said report is to present the design and
construction of the structure of the most compatible basement foundation for the commercial
retail project (Chan & Madabhushi, 2018). Transportation to NSW is responsible for
improving the transportation customer experience service, transportation policy and
regulation, planning and administration of programs, transportation and infrastructure
services and freight. The Program has an objective to attract people back to the city centre by
reinforcing connections between the waterfront and the city, providing job opportunities,
creating more public places and spaces, and developing better transport. The official
governed body has also announced the proper budget for the construction and management of
the building and that is of 500 million dollars. The company wants to build an office with
retail complex and the 1 level parking in basement and for that purpose, they acquire a land at
Honeysuckle, Newcastle CBD.

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Site analysis
Seventeen boreholes have been excavated from the existing basement floor level to depths of
4m and 5m borehole logs are contained within this document. The base condition of the site
consists mainly of sand and gravels and there is a layer of cohesive layer found at six meters
below the ground level.
As per our site conditions and the borehole test results, we will recommend building as the
poured concrete walls type basement. It is the common type of construction for any office. In
this type of construction, we cast the RCC walls on the periphery of the building and
wherever required (Limberger & Bonte, 2017). These RCC walls are long along the floor
height of the basement. These walls not only withstand all the load of the building but also
resist the earth load or the load from neighbouring buildings. This technique of basement
construction begins with spilling the base for the foundation of the basement. When they are
defined, the shapes are come in hand to keep the concrete wall spilt in place for the time
when they are drying. Hollow concrete walls have proved to be stronger when compared to
other kinds of basement walls.
Figure: site plan

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Source: (Limberger & Bonte, 2017)
Suitability and buildability of the various basement
construction methods in response to specific site
conditions
For any work for basements, construction regulations are applicable and cover areas
including ventilation, drainage, roof heights, waterproofing, electrical wiring, water supply,
and means of escape and so on. See the construction regulations for more information.
The basement can be subdivided into three categories, depending on their location,
construction time in relation to the property superstructure above ground and depth. A brief
outline of the differences and the main issues corresponding to each of them are described
below.
Types of Basement
1. Refurbishment
It may be necessary to lower the floor to increase the space of the head, holding adjacent
walls, increasing lighting as well as ventilation. It commonly involves improvements to
existing or a new waterproofing system, and replaced finishes and accessories (Heredia &
García-Sansegundo, 2018). The benefit of this type of basement is that it adds value to the
property and also provides the more usable space.
2. New Garden Basement
New basement can be constructed adjacently to the already existing property, usually in a
garden or backyard space new structure under the ground, with a green roof planted or terrace
at garden level.

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3. Retrofit basement
This type of basement is generally used in the existing buildings. In this type of basement
what we do is we retrofit the existing floor by creating new more space under the existing
floor (Chan & Madabhushi, 2018). It gives more space to the existing building, which can be
used for the different purposes as per the demand and the design.
Common types and methods of Basement construction, which we use:
As per the site condition and the client demand, there are many types and methods of
basement construction, which we use and will discuss now. The main necessity of any
basement is its foundation it provides strength and base to the basement to withstand all the
necessary loads. The base or foundation of the basement not only give resistance to the
different loads but also support the building to withstand against the different climatic
condition, say, wind load, earthquake (dynamically affects the building) load, snow load (in
specified areas according to the government recommended codes) (Teparaksa & Teparaksa,
2018). As per the above-mentioned conditions, we have many kinds of methods to construct a
basement but the most common are stated below:
 Top Down construction
 Vertical cut
 Open cut
BASEMENT CONSTRUCTION METHODS:
Open cut basement construction method:
This method is applied to the shallow basement which needs to be excavated with the sloping
side. The form is considered to be economical because foundation wall is not necessary in

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this case. The angle of slope and the area of ground will be distinguished based on design,
analysis and evaluation result.
Advantages:
 Low budget
 Save construction time for shallow basement
 High quality
 No lateral support (Lin & Chang, 2017)
Disadvantages:
 Not able to use for the deep basement.
 Require large space during the construction process
 High risk of collapsing in high moisture content or flowing water
Application:
 Cohesive soil, less prone
 Small-scale of the basement

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Figure: Open cut
Source: (Teparaksa & Teparaksa, 2018)
Vertical cut construction method:
Bracing excavation method is another name of this method. Unlike an Open cut method,
vertical cut requires a perimeter wall around the area being excavated. On another hand,
perimeter wall is able to replace by secant piling, diaphragm walling and steel piling. During
the construction process, temporary braces and props have to be a part of the system to
maintain the walls.
Advantages:
 Minimize the excavation area
 Keep the side of deep excavation stable
 The effect of the flowing groundwater is reduced
Disadvantages:
 Not able to use for large scale of the basement
 Require temporary system
 Require supporting perimeter wall
 High budget (Ma, Zhang, & Liang, 2018)
Application:
 Small to medium scale basement
 Types of soil depend on the perimeter wall.

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Figure: Vertical cut
Source (Chan & Madabhushi, 2018)
Top down construction method:
Construction of this begins from the top to the bottom of the excavation and the first slab is
completed before starting superstructure construction. Constructing a slab after each stage of
excavation, hence, slabs are considered as a strut in holding earth pressure. The process of
construction is: retaining wall construction and pile construction under the column of the
superstructure; applying formwork and placing columns on piles for the 1st slab at the top,
then, other slabs would be built after each excavation (Chan & Madabhushi, 2018).
Advantages:
 Short time for construction
 Construction area safer as slabs are stronger than struts
 Low risk of ground movement
 Reduce the effect of bad weather
Disadvantages:
 High budget

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 Require complex support construction
 Require lighting and ventilation (Tuan & Tam, 2018)
 Restrict the access of material handling.
Application:
 Very large scale and complex basement.
 Soil nail
EXCAVATION LATERAL SUPPORT SYSTEM:
Sheet pile wall:
Sheeting pile wall is retaining wall that constructed to retain earth, water and any other filling
material. There are 2 types of materials. One is steel pile which is U or Z shape and 12m
long. And another one is reinforced concrete pile which is heavy and bulky. Vibration,
pressing excavation is three methods of installing a sheet pile wall (Lin & Chang, 2017).
The advantage of steel sheeting pile wall:
 Easy to storage and lightweight
 It provides a very high resistance towards the driving stresses
 It is able for reassuring on the various project
 Long service life is made possible in above or below the water
 This is needed to easy to adapt in the pile length
 Joints are found to be less and it is apt in deforming during driving.

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Disadvantages:
 There are sections are found to be rarely used as part of the permanent structure.
 Installation of sheet piles will be difficult in soils with boulders or the cobbles. In
such cases, those desired wall depths cannot be reached.
 Thereby, the excavation shapes are also dictated by the some sheet pile sections as
well as the interlocking elements.
 Sheet pile driving can cause the neighbourhood disturbance (Limberger & Bonte,
2017)
 Settlements is found in the adjacent properties which may take place for
installation vibrations
 High budget.
Application:
 Waterfront structures, i.e. in building wharves, quays and piers.
 Building diversion dams, such as cofferdams
 Riverbank protection
 Retaining the sides of cuts made in the earth.

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Figure: Lateral Support system
Source (Ma, Zhang, & Liang, 2018)
Diaphragm wall:
Diaphragm wall is considered as the reinforced concrete structure which is found to be
constructed in-city in the manner of panel by panel. In this wall it is needed to reach a great
depth, may be up to 50m. For this case, a mechanical excavating method is applied.
Advantages:
 It is can be utilized as the permanent structural wall
 It can be installed within a deeper depth along with for the load-bearing element
 Less temporary for the propping needed
 It can be applied to the top-down construction method
 The rigid structure is required for which the ground movement will be induced by the
basement excavation and that will be less than the other flexible retaining wall
(Vinoth & Ghan, 2019)
 Water retainable
 It is found that the vibration as well as the noise generated from the installation in
case of the diaphragm wall and it would be less than the other methods.
Disadvantages:
 Large site area and limit headroom
 The high cost of mobilization.

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Figure: Diaphragm Wall
Source: (Teparaksa, 2017)
Secant piling:
The secant pile uses concrete of different strengths for a series of piles that overlap each
other, creating a sealed wall face. The primary piles are made with unreinforced concrete.
They are driven first. After they have been allowed to set, they drill for the reinforced
concrete piles, or secondary pile, by drilling into a portion of the primary pile.
Advantages:
 The enhanced construction alignment is flexible enough to fit the complex site
boundaries as well as it is used for maximizing the land used.
 There is the enhanced wall stiffness as compared to the sheet piles. It is also used for
reducing the risk in case of the adjacent ground movements.
 It is also found that this process is suitable for difficult ground with cobbles or
boulders and that is confined with the site space.
 It is used for minimal vibration along with under low noise.
Disadvantages:

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 Difficulty can be raised for joint as well as vertically control
 It will lower the reinforcement efficiency
 Higher cost compared to sheet piles and slow operation
Types of Basement foundations:
Raft Foundations
The Mat Foundations, also known as Raft Foundations, are commonly used when wineries
need to be built. In a mat, the entire slab of the basement floor is found to work as the base.
Thereby, the load of the building is found to be evenly distributed for entire ground cover of
the structure. It is named as the raft because the entire structure is like a boat which floats on
a sea of land. Raft Foundations are used where the floor is not very hard and, therefore,
building weights need to be distributed over a large area, or where the columns are spaced
closely, which means that if the individual bases were constructed, they would overlap.
Figure: Mat Foundation
Source (Limberger & Bonte, 2017)

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Cost comparison of the different type of basement
construction methods
Foundation System
Pad footing Simple and most cost-effective
Raft footing Economic due to combining a foundation
and floor slab
Foundation required less than others
leading to decrease resources/ labour/cost
Strip footing Low cost – long service life
(Teparaksa & Teparaksa, 2018)
Excavation Lateral Support System
Sheet pile Unit cost $40 UC-50
Unit cost $50 UC-75
Expensive and imported
Skilled person needed for carrying out
installations (increase cost) (Tuan &
Tam, 2018)
Diaphragm wall Price N/A
Low cost along with speed construction in
order to have the temporary as well as the

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permanent soil support.
Carry structural load – foundation cost
reduction
High mobility cost
Construction component
Vertical cut It has no actual cost arraignment leading
to the most cost-efficient strategy for
basement construction cost
Top-down It has one of the highest cost for
excavation and faster construction leads to
faster completion
Cost increase due to ELSS support
requirements (Heredia & García-
Sansegundo, 2018)
Economical for multi-level basements
Open cut The best economical choice for
minimization of operation and equipment
leading to lower cost.
The increase of excavation leads to
economic problems
Construction sequencing illustration
1. The first step in the construction is the excavation on the site. Excavation means to
release and remove materials leaving space above or below the floor. Sometimes, at

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the end of civil engineering, grounding is used, which includes the embankment with
new or original materials to annul, spread and equalize over an area. Government
standards provide standards and recommendations for the movement of land covering
the shipment and stakes, levelling and compaction, and the use of earthworks, etc.
Figure: Site Excavation
Source: (Lu & Yin, 2018)
2. Breakout the holes in the ground and the subsoil for the stakes to be built. Includes cut
of existing steel beams covered with concrete inside the slab of the ground floor so that it
can resist more loads and bound with the walls properly.
3. It is needed to construct for underpinning in hit as well as the miss pattern, around its
full perimeter for the area for basement.
4. This is required to adjust the overall raking shores which are mainly propping within
the retaining wall, and for that reason, they take rest on the underpinning along with not
in case of the existing floor slab for the basement (Lin & Chang, 2017).

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5. Open up and decrease the remaining portion within the basement slab level down
towards the top of capping or underpinning beam level.
6. It is needed to dig along with push within the manhole rings for circular stairs. The
holes are needed to make within the manhole rings; it is continued to build the other
lower basement floor slab as well as in-situ where it was facing (in lifts) within the
circular stairwell.
7. After cutting off the top of the piles cast, the capping beam as well as the join ae
needed to underpin as well as in case of in-situ facing in the circular stairs.
8. There is needed to further construct in the in-situ concrete face walls. Firmly they are
connected to face in-situ concrete in the circular stairs.
9. Now, the floor slab of the upper basement floor can be cast.
10. Temporary propping to the continuous piled wall can be removed.
11. The next step is to construct the ground floor slab.
12. There is needed to remove the raking shores which are being propped the basement
retaining wall.
13. Continue with the construction of rest of the building as per plan (Heredia & García-
Sansegundo, 2018).
Conclusion
We have different methods of the basement construction but we decided to use RCC poured
walls basement type. As per our site condition and as per the recommendations of the
geotechnical report we recommend using this method. The advantage of using this type of
method is that the material we are using in our construction is the most common type such as

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concrete with proper strength and it is the most easily available material. This affects the cost
of the basement as there is less money will be required for the transportation of the material.
Not only this the common formwork used for the RCC structures are made up of timber wood
which can be easily transported and also the less skilled labour is required for its stability.
References:
Chan, D. Y., & Madabhushi, S. P. (2018). Centrifuge simulation of heave behaviour of deep
basement slabs in over-consolidated clay. Physical Modelling in Geotechnics., 23-45.
Heredia, N., & García-Sansegundo, J. (2018). The Pre-Andean Phases of Construction of the
Southern Andes Basement in Neoproterozoic–Paleozoic Times. The Evolution of the
Chilean-Argentinean Andes, 111-131.
Limberger, J., & Bonte, D. (2017). A public domain model for 1D temperature and rheology
construction in basement-sedimentary geothermal exploration: an application to the
Spanish Central System and adjacent basins. Acta Geodaetica et Geophysica,, 269-
282.
Lin, P. Y., & Chang, T. K. (2017). Excavation without internal support and its implications in
construction management: a case study. . Journal of GeoEngineering, 81-88.
Lu, K. K., & Yin, J. H. (2018). Modeling Small-Strain Behavior of Hong Kong CDG and Its
Application to Finite-Element Study of Basement-Raft Footing. International Journal
of Geomechanics, 04018104.
Ma, B., Zhang, J. Y., & Liang, F. Y. (2018). Centrifugal Model Tests on the Bearing
Capacity of Piles with Basement Construction Under the Existing Building.
GeoShanghai International Conference, 621-628.

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Teparaksa, W. (2017). Deep Basement Excavation in Soft Bangkok Clay Closed to Palaces.
International Journal of GEOMATE, 85-90.
Teparaksa, W., & Teparaksa, J. (2018). DISPLACEMENT OF DIAPHRAGM WALL FOR
VERY DEEP BASEMENT EXCAVATION IN SOFT BANGKOK CLAY.
nternational Journal, 57-62.
Tuan, B. Q., & Tam, N. M. (2018). Semi top-down method combined with earth-bank, an
effective method for basement construction. IOP Conference Series: Earth and
Environmental Science , p. 012047.
Vinoth, M., & Ghan, S. M. (2019). Support of Deep Excavation Using Contiguous Pile—A
Case Study. . Geotechnical Applications , 273-281.