Design and Construction of Basement with RCC Poured Walls

The assignment content discusses the construction of a basement using RCC (Reinforced Cement Concrete) poured walls. The sequence of construction involves excavation, breakout of holes in the ground, underpinning, and casting the floor slab. The benefits of using this method include the availability and cost-effectiveness of concrete, as well as the ease of transportation and labor requirements for formwork made from timber wood. Additionally, the assignment highlights the importance of maintaining stability during construction and recommends an engineer's design for temporary works.

Construction
Basement

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 report about it is to present the
necessary technical information regarding the project like the construction of the building and the
techniques to be use for its construction. The main purpose of the said report is to present the design
and construction of structure of the most compatible basement foundation for the commercial retail
project. 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
center 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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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 use.
In this office building, we need basement for the parking purpose.
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. The benefit of this type of basement is that
it adds value to the property and also provide 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 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 retrofits the existing floor by creating new more space under the existing floor. 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 different climatic condition, say, wind load, earthquake (dynamically affects the building) load,
snow load (in specified areas according to the government recommended codes). As per the above-
mentioned conditions we have many kinds of methods to construct a basement but the most common
are stated below:
 Poured concrete walls
 Block, masonry walls
 Precast panels
The poured concrete walls or RCC walls basement: In this type what we do is we use RCC retaining walls
to withstand all the loads of the building and also the dynamic loads. In this type of construction, the first
step is to excavate the site for constructing the base of the basement. After that they cast the preferred
sizes of the walls as per the design. It is a very common and easy choice that most people prefer.
Block or wall of masonry in this type of construction we use the concrete blocks for the wall construction
it is also the least expensive for the basement walls. To increase resistibility of the walls sometimes we
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use the reinforcement which affects the cost of the basement as the cost of steel rods are high and, in
that case, we usually use first method of eminent construction
The major disadvantage of the concrete block type of wall is that when it is subjected to the higher loads
it starts getting bending easily which causes the cracks in the basement and later causes the dampness
which is the major wall related issue and it affects the durability of the structure. After it starts bending
the major problem we always face is the weakened adhesive (cemented mortar) joints in the wall. The
basement construction of the prefabricated panel may have problems related to moisture if the beams
are not properly joined, causing moisture content to be entrapped in the panels. These panels may also
attract insects, and they need to be treated with insecticides like boric acid.
In precast panels. In this type of construction, we use the precasted type of walls. Basically, in this
method we do the construction or casting of the walls of the basement elsewhere except the site and
later transport the prefabricated walls to the site and just install it. Proper methodology has been used in
the type of casting like they use proper shaped molds and the material the use in their factory is of best
quality and of proper strength as per the requirement of the design. This type of basement construction
has a high strength, but is not as highly preferred as basements of blocks or lots. precasters provide
panels for walls above the level. The thermo mass system is a sandwich type panel that has internal and
external concrete sayings with a rigid insulation interior, all connected with composite fiber connectors.
Dukane Precast, Naperville, Illinois, produces what they call double wall panels meant to be used in an
entire house - walls, floors and even the deck floor. 2/8-inch-thick inner and outer concrete nozzles are
fused together, held together by wire trellis. The rough and plumbing are installed in the cavity and the
vacuum is filled with foam insulation. The panels are connected with a high strength mortar filling.
Dukane says that a medium-sized house can be erected in about five days, although this is preceded by
several weeks of planning.
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The panels above the upper level of the upper walls are practically the same as the wall panels of the
foundation. They were used to build three-story structures (one foundation wall and two levels above
the level). The panels can be designed for any desired architecture feature.
Existing condition of the site for the basement and adjacent structures.
Seventeen boreholes have been excavated from 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 bore hole test results. We will recommend to build 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. These RCC
walls are long along the floor height of the basement. These wall not only withstand all the load of the
building but also resist the earth load or the load from neighboring buildings This technique of basement
construction begins with spilling the base for foundation of the basement. When they are defined, the
shapes are come in hand to keep the concrete wall spilled 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.
Types of Basement foundations:
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1. Shallow foundations
Isolated foundations are also known as scattered bases and open foundations. The word "open"
points to the fact that these foundations are constructed by excavating all the earth to the base
of shoe and then building the base. During the first stages of work, the entire base is open to the
workers and therefore is known as the “open foundation”. The methodology is that each shoe
transfers the concentrated load of the column and rests it over a large area, so that the actual
load intensity on the ground does not surpass the safe load bearing capacity of the soil.
In cold regions, surface foundations need to be protected from freezing. The condition occurs
because the water content in the earth close to the foundation can freeze and expand, thus
harming the foundation structure. These foundations must be built below the freezing line,
which is the level on the ground above which freezing occurs. If the substructure cannot be built
below the freezing line, it needs to be protected using insulation: usually a bit of building heat
penetrates the ground and prevents freezing. Individual bases are one of the simplest and most
common kinds of foundation structures. These are widely used when the load of the structure is
transported using columns. Normally, each column should have its own foundation.
The base maybe a square or rectangular concrete platform out of which the column rises. To
have a very rough estimate of the dimensions of the base, the engineer can calculate the total
load acting upon the column and divide it by the safe load bearing capacity (SBC) of the soil.
Taking an example, let a column have a vertical load of say, 10T and the safe bearing capacity of
the soil is 10T/m2, the required area of the base will be approximately 1m2. In practice, the
designer needs analyze many other factors before making a construction drawing for the base.
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Isolated foundations
2. Strip Foundations
Strip foundations are usually preferred in load-bearing masonry/brick structures, and behave as a long
strip that transfers the weight of an entire wall to the ground. These foundations are recommended
where entire walls instead of isolated columns carry the construction and service loads, such as in old
structures made of masonry.
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3. Mat or 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 works as the base; the load of the building is evenly
distributed over the 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.
Mat Foundation
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4. Pile foundations
A pile is just a long cylindrical structure made of a high strength material, like concrete, that is forced
towards the ground, so that it can support structures built on it.
The pile foundations are favorable in the given conditions:
1. When the layer of sub soil or base soil is very weak. This layer may be unable to support the
loads of the structure, so building weights have to surpass this layer and be transmitted to the
strongest soil layer or rock if found below weak layer.
2. When a structure has quite heavy weights and they are directly transmitted to the foundation, as
in a tall building. Pile foundations are capable of withstanding larger loads than strewn ridges.
Pile foundations
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Design of basement walls
On a Professional scale, the correct RCC design to support Type A barrier protection can be determined
from the proper government codes document. RCC walls and subsoil slabs, especially the ones used as
structural protection, need a lot of detailed structural calculations. The calculations consider soil, water
table, method of constructing and performance required to calculate the quantity of reinforcement
needed for the specific sections of concrete. When stacking becomes necessary, for example, a more
specialized project will be necessary and this must be incorporated into the complete structural project.
In regards to protection, the common design - that is, with controlled protuberances and corners - will
allow the installation of moisture proofing membranes. The granular filling as well as drainage at the
front of the wall will minimize the accumulation of hydrostatic pressure. Also, avoid inverted corners in
the plane that are facing upwards - they may intercept groundwater. We use the different structural
software’s for the RCC designs we usually we use Staad pro for the design.
3D sample of Basement
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Sample Plan view of the basement
Sample Building model view on site
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BASEMENT CONSTRUCTION METHODOLOGY
1. The intention is built a basement floor which is 3.6 m down from grade level for the parking
purpose in the office building. Further, the basement floors are proposed to be built under part
of the existing basement footprint.
2. The consequence of this will be that the basement walls on all elevations will be undermined.
Basement floor slab will also eradicate the propping to the base of the retaining wall elements.
3. Corrective action is necessary to ensure that, under both temporary and permanent conditions,
the elements of the retaining wall remain effectively supported at the level of the existing
subsoil, and that the risk of weakness is mitigated. The existing walls in the perimeter of the
basement will remain supported vertically through the construction of reinforced concrete
supports below the basement walls. The same base will also serve to provide the "support action
to the base of the retaining wall elements (currently supplied by the floor slab).
4. An Insetu concrete face will be constructed immediately in front of the adjacent stacked wall, and It
will connect positively to the stacked wall.
5. Due to the criticality of the temporary works, maintaining the stability of the works, all
construction jobs must be subject to an engineer’s design.
SEQUENCE OF CONSTRUCTION
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 floor. Sometimes, at 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 provides standards and
recommendations for the movement of land covering the shipment and stakes, leveling and
compaction, and the use of earthworks, etc.
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Site excavation
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. Construct underpinning in hit and miss pattern, around the full perimeter of the area for
basement.
4. Adjust the raking shores that are propping the retaining wall, so that they rest on the
underpinning and not on the existing floor slab of basement.
5. Open up and decrease the remaining portion of the basement slab level down to top of capping
or underpinning beam level.
6. Dig and push the manhole rings to the circular stairs. Make holes into the manhole rings,
continue to build the lower basement floor slab and insitu facing (in lifts) inside the circular
stairwell.
7. After cutting off the top of the piles, cast the capping beam and join it to the underpinning and
insitu facing in the circular stairs.
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8. Construct the insitu concrete face walls. Firmly connect the facings to the insitu concrete in the
circular stairs.
9. Now, the floor slab of the upper basement floor can be casted.
10. Temporary propping to the continuous piled wall can be removed.
11. The next step is to construct the ground floor slab.
12. Remove the raking shores that are propping the basement retaining wall.
13. Continue with the construction of rest of the building as per plan.
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Advantages and Disadvantages of RCC wall basement
There are many uses of basement as per the client. As in our case we will use it for car parking as per the
client demand. But there are many cases in which basement got some negative points also. Firstly, if the
basement is of no use or the property owner didn’t use it then it will be waste of the money as the cost
of the construction is quite high as per the normal floor construction and the main reason behind it is
because of the use of RCC walls. In most of the cases the basement is subjected to the moisture and
other underground chemicals as the basement of the building is under the ground and the walls on the
periphery of the plot will be subjected to the saturated soil.
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 geotechnical report we
recommend to use 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 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 form work used for the RCC
structures are made up of timber wood which can be easily transported and also the less skilled labor is
required for its stability.
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References
1. Everything you need to know about basement construction.
https://edensstructural.com/everything-need-know-basement-construction
2. HARRIET WALK, LONDON (2012). BASEMENT CONSTRUCTION METHODOLOGY
3. Basement Excavation - Designing Buildings
https://www.designingbuildings.co.uk/wiki/Basement_excavation
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