Construction �Technology

Dr Adewale Abimbola, FHEA, GMICE

aabimbola@cavc.ac.uk

Aim and Objectives

Aim: Substructure Works.

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Objectives: At the end of the lesson, the students should be able to:

• Describe basement construction works through use of underpinning, steel sheet piling, diaphragm walls, etc.
• Discuss excavation and traditional techniques for basement construction works.
• Describe in and near water construction works through use of cofferdams, caissons, etc.
• Describe drainage works through use of culvert.

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LO3 | P7. Learning Outcomes and Assessment Criteria

Basement Construction

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Introduction

• Basement construction is a complex form of building and involves a combination of geotechnical, hydrological, structural and civil engineering, health and safety, and waterproofing expertise.
• Associated health and safety problems include:
• fatalities, injuries, building collapses, partial building collapses, negative impacts on residents living near basement construction projects, and other damage to structures.

Basement types based on depth in existing structure can be classified as:

• Cellar extensions
• Single level basements
• Multi-level basement

Main factors for consideration.

Basement Types - Cellar extensions

• This is the least complex form of retro-fit construction. Generally, the existing walls are underpinned to extend the existing foundations downwards, increasing the head height of the existing cellar or vaults.
• A new floor slab is constructed, and an appropriate waterproofing system is installed to protect the new basement from water ingress through both the existing and new structures.

Cellar extension.

Basement Types: Single-level Basements

• Single-level basements involve creating one new level of basement below the level of the lowest internal floor or below a garden.

Basement Types: Multi-level Basements

• Multi-level basements involve creating more than one new level of basement below the existing lowest floor level of a building or below the garden.

Single-level basement..

Multi-level basement..

Basement Construction Techniques

• The techniques used to build the main structural elements of a basement.
• The techniques include:
• Underpinning
• Cofferdam
• Diaphragm walling
• Etc.

Basement Construction Technique - Underpinning

• It is the method of supporting the structures while providing new foundations or carrying out repairs and alterations without disturbing the stability of existing structures.
• It is carried under following conditions:
• To protect an existing structure from the danger of excessive or differential settlement of foundation.
• To improve the bearing capacity of foundation so as to sustain heavier loads for which deepening or widening of foundation is done
• To provide a basement for an existing structure.
• It is more economical, due to land price or otherwise, to work on the present structure's foundation than to build a new one.
• When a building with deep foundation is to be constructed adjoining a building which is built on shallow footings. Here the shallow footings should be strengthened first.

Basement Construction Technique - Underpinning

Precautionary Measures

• Before implementing appropriate underpinning measures, the following important points should be carefully attended:

 The existing structure should be fully examined carefully, and appropriate underpinning method should be adopted.

 All poor masonry work, such as joints, cracks, plastering should be rectified before commencing underpinning.

 Necessary shoring and strutting should be done such that existing structure is safe.

 Adequate care should be taken to ensure that there should be no movement of structure for which levels should be marked.

Basement Construction Technique - Underpinning

Process of Underpinning

• Underpinning is accomplished by extending the foundation in depth or in breadth, so it either rests on a more supportive soil stratum or distributes its load across a greater area.
• Use of micro-piles and jet grouting are common methods in underpinning.
• An alternative to underpinning is the strengthening of the soil by the introduction of a grout.
• All these processes are generally expensive and elaborate.

Types of Underpinning

Mass Concrete Underpinning

 Beam and base underpinning

Micro-piled/Mini-piled underpinning

 Chemical method

Basement Construction Technique - Underpinning

Mass Concrete Underpinning

• Also known as 'traditional underpinning, 'This underpinning method strengthens an existing structure's foundation by digging boxes by hand underneath and sequentially pouring concrete in a strategic order. The final result is basically a foundation built underneath the existing foundation.
• This underpinning method is generally applied when the existing foundation is at a shallow depth.
• The method has not changed since its inception with its use of utilitarian tools such as shovels and post hole diggers.
• Heavy machinery is not called for in this method due to the tight nature of the boxes being dug.

New Basement - Crawlspace dig out and underpinning - YouTube

Basement Construction Technique - Underpinning

Beam & Base Underpinning

• The beam and base method of underpinning is a more technically advanced adaptation.
• A reinforced concrete beam is constructed below, above or in replacement of the existing footing. The beam then transfers the load of the building to mass concrete bases, which are constructed at designed strategic locations.
• Base sizes and depths are dependent upon the prevailing ground conditions. Beam design is dependent upon the configuration of the building and the applied loads.

Basement Construction Technique - Underpinning

Micropiles

• Micropiles have the greatest value where ground conditions are very variable, where access is restrictive.
• Micropiled underpinning is generally used when the loads from the foundations need to be transferred to stable soils at considerable depths - usually in excess of 5.0 metres.
• May either be augured or driven steel cased and are normally between 100mm and 250mm in diameter.
• It is used to stabilise or upgrade existing foundation by installing micropiles through pre-drilled holes determined by load characteristics.

Foundation Repair using Push Piers - YouTube

Foundation Repair with Helical Piers and Push Piers - YouTube

Basement Construction Technique - Underpinning

Micropiles

• Micropiles are described as small diameter piles that can be installed in almost any type of soil and that can carry loads up to 500 tonnes depending on the type of it.
• These micropiles are steel reinforced placed into a small diameter hole and scaled to the ground by grout injections under relatively high pressure.
• Micropiles are widely recognised as a common remedial option for underpinning structures having foundations problems after completion or during service period.

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Types of Micropiles

 Pile and Beam/Needle.

 Pile and Cantilever Beam.

 Piled raft.

 Angle pile.

 Jack Down piles.

Cantilever needle beam method

the underpinning steel pipe pile press fit technique

Basement Construction Technique - Underpinning

Advantages of Micropiles

i. They have high carrying capacity.

ii. Less site constraint problems.

iii. Low noise and vibration causes little disturbance.

iv. It is a self–sustained operation.

v. They can be installed close to existing walls with limited headroom and congested site conditions.

vi. They are small, relatively light and inexpensive.

Basement Construction Technique - Underpinning

Chemical Method

• In this method the foundation soil is consolidated by employing chemicals.
• Perforated pipes are driven in an inclined direction beneath the foundation. The slopes are provided such that the entire area under the existing footing comes under the area used to be strengthened.
• After the pipes are installed, solution of sodium silicate in water is injected through the pipes. This is a two-injection method. The pipes are withdrawn and at the time of withdrawal of pipes, calcium or magnesium chloride is injected through pipes.
• Chemical reaction takes place between these two chemicals, and the soil is strengthened by consolidation. This method is suitable for granular soils

Treating house subsidence in Croydon

Basement Construction Technique – Deep Excavation – Dumpling Method

Dumpling Method

• This is used where there are buildings or street in the proximity. The method is to construct a series of retaining wall in trench, section by section, around the site perimeter ,leaving a centre Called "dumpling“.
• When the perimeter walls are in place, excavation may start at the centre of the dumpling, until exposing a section of the wall. Then the wall may be side supported by struts, shoring or soil anchor etc., again section by section in short length, until the excavation is all completed.
• This method does not require much heavy mechanical equipment and thus cost of work is relatively lower. It can excavate up to a maximum depth of about 3m. Sometimes in very poor soil or in waterlogged ground, interlocking steel sheet pile may be driven to confine the area to be excavated.
• By the using of sheet pile, excavation may reach maximum to about 15m. However, the cost of work will be increased.

Excavation and construction of shallow basement using dumpling method.

Deep Excavation Technique for Basement Construction – Cofferdams

• A cofferdam may be defined as a temporary box structure constructed in earth or water to exclude soil or water from a construction area, such as for foundation or basement works.
• Use of cofferdam suitable for excavation of larger scale can be of :

a) Sheet pile cofferdam – Also known as single skin cofferdam. Interlocking type steel sheet pile is used and can use for excavation up to 15m. Sheet pile in this case acts as a cantilever member to support the soil therefore adequate depth of pile or suitable toe treatment may be required. In addition, cofferdams are needed to be braced and strutted or anchored using tie rods or ground anchors.

b) Double skin cofferdam – This works similarly like the sheet pile to form a diaphragm. However, the diaphragm is double-skinned using two parallel rows of sheet pile with a filling material placed in the void between. This creates somewhat a gravity retaining structure and increase the ability to counteract the soil behind. However, more working space is required.

amazing sheet pile driving

Deep Excavation Technique for Basement Construction – Diaphragm Walling

• This method need to construct a R.C. retaining wall along the area of work. Because the wall is designed to reach very great depth, mechanical excavating method is employed.
• Typical sequence of work includes:
• Construct a guide wall.
• Excavation for the diaphragm wall.
• Excavation support using bentonite slurry.
• Insert reinforcement and concreting.

Diaphragm Wall Construction

Deep Excavation Technique for Basement Construction – Ground Anchor

• Ground anchor is basically a pre-stressing tendon embedded and anchored into soil or rock to provide resistance to structural movements by a “tying back" principle.
• Common applications are:
• General slope stabilisation
• Tying back/stabilising a retaining structure
• Tying back/stabilising for diaphragm walls, but for a temporary nature during excavation
• Tying back the entire building from up possible uplifting

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• Ground anchor can be classified into:
• Rock anchor – for anchorage in rock
• Injection anchor – suitable for most cohesive and non-cohesive soils

Soil and Rock Anchors

Basement Construction - Using Traditional Methods

• Construction of basement is difficult for it must be carried out below deep ground in adverse condition such as existence of ground water, muddiness or limited working space.
• Besides, works are needed to be done amidst layers of props, struts, walings and shores, which cannot be removed until the permanent works are completed and capable of carrying the final loads.
• For each case of basement construction, the method of soil support, sub-soil condition, structure of the basement as well as the layout requirement of the entire building must be taken into consideration before designing the method of works.
• One of the most effective methods to construct ordinary basement is using diaphragm wall or sheet pile wall which serves as a retaining structure during excavation and as the sides of the basement walls

Basement Construction - Using Traditional Methods

1. Use of lattice beams: A series of lattice beams or steel trusses are installed so that they span between the top of opposite diaphragm walls enabling them to act as propped cantilevers. The trusses can be removed after the internal floors have been constructed and receiving all the lateral forces from soil.

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• Use of Ground Anchors: Diaphragm walls are exposed by carrying out the excavation in stages and ground anchors are provided to stabilise the walls as the works proceeds. This method is most effective for basement of very large span or without intermediate floors as lateral support

One Burrard Place - One of the deepest excavations (105ft) in Vancouver history

Excavation and basement construction - YouTube

Basement Construction - Using Traditional Methods

3. Construct floor slab as support (top-down method)

• After the perimeter diaphragm walls have been constructed, the ground floor slab and beams are cast providing tip edge lateral support to the walls. An opening is left in the slab for labours, material or plant as access to continue excavation to the lower stages. This is repeated until the required depth is reached.

Basement Excavation Support using Shore or Strut from a Central Basement Slab cast in advance phases

Basement Excavation Support using Ground Floor Slab (Simple Top-down Approach)

Top Down Construction Excavation Process

Top Down Construction Method (basement)

4. Cast the centre basement slab to support struts

• Centre area between the diaphragm walls can be excavated leaving an earth berm around the perimeter to support the walls whilst the lowest basement floor in centre can be constructed. Slots to accommodate raking struts acting between the wall face and the floor slab are cut into the berm. Final excavation and construction of the remaining of the basement can take place in stages around the raking struts.

Complex 5 level basement excavation procedure sets footprint for 'The Imperial'

Basement Construction - Using Traditional Methods

Removal of Soil

There will have great amount of excavated soil produced during the process of excavation

Soil removal can be done by the following ways.

1. Using manual method, say, by wheelbarrow.
2. Using bucket and lift to ground level by crane.
3. Using hoist rack (opening has to be provided in the basement/excavation pit first).
4. Using gantry crane (opening has to be provided in the basement/excavation pit first).
5. Using conveyor belt
6. Using excavating machine to removal spoil, may be in stepped position in case of very deep pit.
7. Using dump truck but access provision has to be provided in advance (such as a temporary ramp or the permanent vehicular access into a basement)

Excavating machine to take up spoil from below

Remove spoil by clamp shell/steel bucket

Hoisting machine is provided for removing spoil from basement

Using of a gantry crane for spoil removal

https://www.youtube.com/watch?v=EE36cai9y18

Self-assessment Task

Describe any two types of basement construction methods commonly undertaken by civil engineers.

Your answer should demonstrate an understanding of why and how each method is used, the construction process involved, and its application within different site conditions.

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Hint: references to

- The use of steel underpinning, sheet piling, diaphragm walls, cofferdam, etc.

Note:

• Paragraphs of about 6-8 lines for each of the two types.
• Use illustration to support your description.
• Ensure you provide intext citations and sources of the information.

In or Near Water Construction

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Introduction - In or Near Water Construction

 During the construction of bridges, dams or any other structure where the foundation part of the structure is most likely to lie underwater, we must opt for underwater construction.

Construction in water poses many difficulties especially in the places where there is large water depth.

During underwater construction, our main objective is to create dry and water free environment for working in such a manner that the structural integrity is not compromised.

In or Near Water Construction - Caissons

• A permanent watertight retaining structure for the purpose of excavating and executing work at a prescribed depth.
• May be constructed of steel, cast iron segments or reinforced concrete, or a combination of these materials.
• Used to work on foundation of bridge pier, construction of concrete dam or for the repair of ships.
• Constructed in such a manner so that the water can be pumped out and keeps working environment dry.
• Sides constructed free from bulges and constructed so as not to lose their shape during sinking.
• Steel caissons could be strengthened by insitu concrete. between inner and outer walls to prevent buckling and to add weight to prevent floating.

Caisson technology in the construction of port infrastructures - YouTube

In or Near Water Construction - Caissons

• There are four types of caisson as follows:

 Box Caisson.

 Open Caisson.

 Compressed air Caisson.

 Monoliths

In or Near Water Construction - Caissons

BOX CAISSON

• They are prefabricated boxes, usually in concrete, with sides and a bottom, which are set on prepared base.
• The box is then filled with concrete to form a massive foundations for a pier or similar structure.
• Setting caisson on a piled foundation to act as anchorage against buoyancy, may be used where foundation is subject to erosion by fast moving water

OPEN CAISSON

• Open Caisson: are structures which are open at both top and bottom.
• Suitable where the sub-stratum is soft clay or silt and therefore easily excavated by grab.
• The caisson is sunk by grabbing the soil through the open wells. When it has reached the desired depth, the bottom is then plugged with a layer of concrete, and the well is pumped dry.

In or Near Water Construction - Caissons

COMPRESSED AIR CAISSON

• Suitable for sinking foundations in troublesome ground, e.g. ground containing obstacles that require moving by hand
• Caisson is sunk and soil is excavated by hand with aid of pneumatic tools & loaded into skips for hoisting up through the muck-lock.
• The top of pneumatic caisson is closed and contains a working chamber at which pressure greater than atmosphere is maintained to exclude water from entering the working chamber enables the excavation.

MONOLITHS

• Similar to open caisson but differ in that they are much heavier.
• It consists of RC walls of substantial thickness to provide sufficient weight to prevent overturning: For this reason, they are often used for quay walls which must resist great impact forces from ships coming in to berth.

In or Near Water Construction - Caissons

Advantages

• The caisson can be extended up to large depths.
• Caissons are more suitable for the deep foundation under water where the foundation should be extended up to or below the riverbed so as to obtain the proper stability.
• Cost of Construction is relatively less on bed level or lower side.
• Quality control of pneumatic caisson is good because work is done in dry conditions. Concrete gain more strength due to dry conditions.
• In-situ soil tests are possible to determine the bearing capacity of pneumatic caisson.
• There is direct and easy passage to reach the bottom of caisson, hence any obstruction can easily be removed.

Disadvantages

• In box caisson the placing of concrete is done for concrete seal under water, it may not be satisfactory.
• If any obstruction of boulders or logs are encountered, then progress of work becomes slow.
• The help of divers may be required for excavation near haunches at the cutting edges.
• Construction of pneumatic caissons is much expensive than open caissons.
• During working the various constructional activities, a proper care has to be taken, otherwise it may lead to fatal accidents.
• Labour cost is high.

In or Near Water Construction - Caissons

Dangers Encountered

• Caisson disease is so named since it appeared in construction workers when they left the compressed atmosphere of the caisson and rapidly re-entered normal (decompressed) atmospheric conditions.
• Construction of the Brooklyn Bridge, which was built with the help of caissons, resulted in numerous workers being either killed or permanently injured by caisson disease during its construction, including the designer's son and Chief Engineer of the project.

• Workmen may suffer from giddiness.
• There is pains in ears of workmen.
• There is breaking of ear drums of workmen.
• There is bursting of blood vessels in the nose or ears of workmen.

• It may cause paralytic death.
• If the bubbles are developed in spinal cord, it causes paralysis and if the bubble are developed in heart, it causes heart attack.
• Caisson diseases can be controlled by recompression followed by slow decompression

Caisson Diseases

In or Near Water Construction - Cofferdams

• Temporary structure.
• Built within or in pairs across a body of water.
• Allows the enclosed space to be pumped out, creating a dry work environment.
• Enclosed coffers are commonly used for construction and repair of oil platforms, bridge piers and other support structures built within or over water.
• A cofferdam involves the interaction of the structure, soil, and water. The loads imposed include the hydrostatic forces of the water, as well as the dynamic forces due to currents and waves.
• Used for shallow constructions having depth less than 10m.

Components of Cofferdams

• Sheet piling Sheet piling is a manufactured construction product with a mechanical connection “interlock” at both ends of the section. These mechanical connections interlock with one another to form a continuous wall of sheeting.
• Brace piling
• Concrete seal

Gravity Cofferdams

• Earth & rock-fill cofferdams are the most common gravity type. They are enclosures formed by banks of soil or rock
• Suitable for protecting large areas of excavation against flood waters and re best constructed in the dry during low-water periods.
• If velocity of flow is small and pressure head is low, then earth fill is suitable; if velocity of water is likely to be high, rock fill offers better resistance to scouring

Sheeted Cofferdams

• Steel sheeting can be divided into two distinct types:
• Single skin: has one or more vertical stages
• Double skin: consists of two lines of sheet piles or circular cells of sheeting filled with rock or other material. The width of dam should not be less than 0.8 times the height of retained water and/or soil.

Cofferdam - YouTube

Building a pair of Cofferdams in the Big Muddy River in southern Illinois - YouTube

Advantages of Cofferdams

• Allow excavation and construction of structures in otherwise poor environment.
• Provides safe environment to work.
• Contractors typically have design responsibility.
• Steel sheet piles are easily installed and removed.
• Materials can typically be reused on other projects.

Underwater Concreting

• It is a process in which the prepared concrete is poured below the water surface by using suitable methods.
• Placement methods include:
• Tremie method
• Pump method
• Placing by skip

Underwater Concreting

Tremie method

• A Tremie is a watertight pipe.
• Generally 200 - 250mm in dia.
• Funnel shaped hopper at its upper end and a loose plug at the bottom.
• It is supported on a working platform above water level.

Underwater Concreting

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Pump Method

• Pumping concrete directly into its final position, involving both horizontal and vertical delivery of concrete.
• Pumping concrete has the advantage of operational efficiency with potential savings of time and labour.
• For massive underwater concrete construction of navigation structures, the pump method should be prohibited.

Placing by Skip

• Skips used for underwater concreting should be of the bottom opening type which can be operated automatically or manually
• Skip may also be fitted with a skirt to confine the concrete on release
• Choice between placing by skip or by tremie rests on economics and the plant and skills which are available.
• Placing by skip is the slower but more practical for thin beds, whereas tremies are suitable for large concrete pours

Culvert

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• Culvert is defined as a tunnel structure constructed under roadways or railways to provide cross drainage or to take electrical or other cables from one side to other.
• It is totally enclosed by soil or ground.
• Culverts are like pipes but very large in size.
• They are made of many materials like concrete, steel, plastic, aluminium, high density polyethylene.
• In most cases concrete culverts are preferred. Concrete culverts may be reinforced or non-reinforced. They may be cast in situ culverts or precast.

• Types include:
• Pipe culvert
• Pipe arch culvert
• Box culvert
• Arch culvert
• Bridge culvert

Culvert

Pipe culvert

• Pipe culverts are widely used culverts and rounded in shape.
• The culverts may be of single in number or multiple.
• The diameter of pipe culverts ranges from 1 meter to 6m.
• These are made of concrete or steel etc..

Pipe Arch culvert

• They are half circle shaped culverts.
• Because of arch shape fishes or sewage in the drainage easily carried to the outlet without stocking at the inlet or bottom of channel.

Box culvert

• They are in rectangular shape. Concrete and reinforcements are used.
• Because of sharp corners these are not suitable for larger velocity.

Culvert

Arch culvert

• Arch culvert is similar to pipe arch culvert but in this case an artificial floor is provided below the arch.
• The artificial floor is made of concrete and arch also made of concrete. Steel arch culverts are also available but very expensive.

Bridge culvert

• Bridge culverts are provided on canals or rivers and also used as road bridges for vehicles.
• For this culverts a foundation is laid under the ground surface. A series of culverts are laid and pavement surface is laid on top this series of culverts.
• Generally these are rectangular shaped culverts these can replace the box culverts if artificial floor is not necessary.

Self-assessment Task

Describe any two types of substructure works undertaken by civil engineers.

Your answer should demonstrate an understanding of why and how each method is used, the construction process involved, and its application within different site conditions.

​

Hint: consider one for each below

- In or near water construction works through use of cofferdams, caissons, etc.

- Drainage works through use of culvert.

Note:

• Paragraphs of about 6-8 lines for each of the two types.
• Use illustration to support your description.
• Ensure you provide intext citations and sources of the information.

References/Bibliography

ASUC (2016) Guidelines on safe and efficient basement construction directly below or near to existing structures. Available at: https://www.basementforce.co.uk/files/asuc-basement-guidelines-2nd-edition-july-2016.pdf (Accessed: 10 February 2025)

Const-infobank. (n.d.) Excavation and basement construction. Available at: https://const-infobank.org/wp-content/uploads/2016/12/Principle-about-basement-construction.pdf (Accessed: 10 February 2025)

Holmes, R. (1996) Introduction to civil engineering construction. College of Estate Management.

The Constructor (2023) What is culvert? Its types, materials and location. Available at: https://theconstructor.org/construction/types-of-culverts-material-construction/12926/ (Accessed: 10 February 2025)

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