UNIVERSITY OF SOUTH AFRICA (UNISA)
College of Science, Engineering & Technology
⋄
ASSIGNMENT 2
Year Module — 2026
⋄
Module Code: CMT2601
Module Name: Construction Methods
Assignment No.: Assignment 2
Due Date: 2026
Semester: Year Module 2026
Submitted in partial fulfilment of the requirements for Construction Methods (CMT2601)
at the University of South Africa.
,UNISA | CMT2601 Construction Methods – Assignment 2
Question 1: Risk Assessment Before Construction on Large Infrastructure Projects
1.1 Why a Risk Assessment Must Be Conducted Before Starting Construction on Large
Infrastructure Projects
Question: Explain why a risk assessment must be conducted before starting construction
activities on large infrastructure projects such as harbours, railways, or airports. [5 marks]
Large infrastructure projects – harbours, railways, and airports – are some of the most com-
plex undertakings in civil engineering. They involve a combination of heavy equipment, large
workforces, hazardous environments, and considerable financial investment. Before any ground
is broken, a structured risk assessment is not just recommended; it is a professional and legal
obligation (De Mare et al., 2018). The following points explain why.
1. Identifying Hazards Before They Cause Harm
Construction sites at ports and airports expose workers to risks that are not always obvious
at the outset – deep water edges, overhead power lines, unstable ground, and high-volume
machinery often operate in the same space. A risk assessment forces a systematic look at
what could go wrong. Spotting these hazards on paper is far cheaper than dealing with an
injury or fatality on site (Tepeli, 2020). ISO 31000:2018, the international standard on risk
management, requires that risk identification precede all project activities so that mitigation
measures can be built into the construction plan.
2. Legal and Regulatory Compliance
South African law, through the Occupational Health and Safety Act 85 of 1993 and its Con-
struction Regulations, requires contractors to prepare a documented risk assessment before
work begins. Non-compliance exposes the principal contractor and client to criminal liability,
civil claims, and project stoppages. For large state-funded infrastructure – a new harbour ex-
pansion or airport terminal – the consequences of non-compliance can be especially severe, as
regulatory bodies and oversight authorities scrutinise such projects closely.
3. Protecting Workers, the Public, and the Environment
Harbours and airports are operational environments. Construction activity at a functioning
harbour, for instance, happens close to live vessel traffic and active cranes. Without a risk
assessment, the construction team has no structured basis for deciding where to erect barriers,
where to restrict public access, or how to protect sensitive marine ecosystems from construc-
Page 1 of 17
,UNISA | CMT2601 Construction Methods – Assignment 2
tion runoff. The MDPI journal on sustainable civil infrastructure assessment confirms that in-
frastructure projects carry significant environmental and social risks throughout their lifecycle
and that proactive risk evaluation is central to responsible project management (Sustainable
Assessment of Civil Infrastructure Systems, 2022).
4. Financial Planning and Cost Control
Unidentified risks are the leading cause of cost overruns on large civil projects. Gorecki and
Diaz-Madronero (2020) found that qualitative risk analysis on road and motorway projects,
using national risk registers and Monte Carlo simulations, allowed project managers to map
dependent cost variables and prepare more realistic budgets. The same logic applies to har-
bours and airports. A risk assessment lets the project team ring-fence contingency funds for
probable risk events rather than reacting to surprises mid-construction.
5. Informing the Construction Method Statement
A risk assessment directly feeds into the Method Statement – the document that prescribes
how each work activity will be carried out safely. Without the risk assessment, the Method
Statement is incomplete. For a railway construction project, for example, identifying the risk
of track geometry failure under heavy freight loads informs decisions about ballast specifica-
tion, sleeper spacing, and subgrade preparation well before a rail is laid.
Critical Consideration
Under South African law, the Construction Regulations of 2014 (promulgated under
the OHS Act 85 of 1993) make it a criminal offence for a contractor to commence any
construction work without an approved risk assessment and health-and-safety plan.
This requirement is non-negotiable regardless of project size.
Page 2 of 17
,UNISA | CMT2601 Construction Methods – Assignment 2
Question 2: Quay Wall Construction – Site Safety and Harbour Operations
2.1 How Strong Wave Action Affects the Structural Stability of a Quay Wall Under
Construction
Question: Explain how strong wave action can affect the structural stability of a quay wall
under construction. [5 marks]
A quay wall is a gravity or retaining wall structure that simultaneously provides shore pro-
tection and a berthing face for vessels (International Coastal Engineering, 2017). During con-
struction, before the wall has reached its full design mass and before all foundation grouting
and backfill compaction is complete, it is particularly exposed to wave-induced forces. The fol-
lowing mechanisms explain how strong wave action destabilises a quay wall mid-construction.
1. Hydrostatic Pressure Imbalance and Overturning
Every wave cycle exerts alternating positive pressure on the seaward face and negative suction
on withdrawal. On a partially completed caisson or sheet-pile quay wall, this cyclic loading
creates a rocking effect. Research on caisson-type quay walls confirms that the phase relation-
ship between wave action and structural response significantly affects displacement and the
risk of overturning, particularly when the structure has not yet achieved its full dead weight
(Numerical Studies on the Stability of Caisson Quay Walls, Ocean Engineering, 2024).
2. Scour at the Foundation
Wave energy reaching the base of a quay wall during construction can dislodge loose rubble
mound material or erode the seabed substrate beneath the foundation. This is called scour.
When the bearing layer is removed or loosened, the wall can settle unevenly or tilt seaward. A
quay wall still in the process of being seated on its rubble base is especially vulnerable because
the rubble has not yet been consolidated by the full weight of the completed structure.
3. Liquefaction of Saturated Backfill
Backfill placed behind a quay wall during construction is often in a loose, saturated state be-
fore compaction is complete. Repeated wave-induced pressure cycling can cause pore water
pressure to build up in this backfill, temporarily transforming it from a solid-like material into
a fluid-like one. This is soil liquefaction. When the backfill liquefies, the lateral earth pres-
sure on the wall increases dramatically, pushing the wall seaward beyond its design resistance
(Emerald Publishing, Geotechnical Research, 2022).
Page 3 of 17
, UNISA | CMT2601 Construction Methods – Assignment 2
4. Structural Fatigue and Joint Failure
Steel sheet piles, tie-back anchors, and concrete panel joints that are not yet fully installed
are especially susceptible to wave-induced vibration and fatigue. Repeated stress cycles can
open joints, loosen connections, or cause premature cracking in unreinforced concrete sections.
Once a joint fails, water infiltrates the structure, accelerating corrosion and further degrading
structural integrity.
5. Wave Overtopping and Instability of Construction Plant
In rough sea conditions, waves overtopping the wall crest flood the working platform behind
it. This removes any safe operating base for construction equipment, and – more critically
– the added water mass on the landward side changes the load distribution on the partially
completed wall, potentially triggering sliding failure along the foundation plane.
Quality Assurance
Construction of quay walls should be suspended when significant wave height exceeds
the design threshold for the construction stage in use. Site supervisors must monitor
wave forecasts daily and have a documented weather-stoppage protocol that defines the
trigger conditions for evacuating the marine work zone.
2.2 How Sediment Buildup at the Harbour Entrance Affects Harbour Operations and
Vessel Movement
Question: Discuss how sediment buildup at the harbour entrance can affect harbour opera-
tions and vessel movement. [4 marks]
Sedimentation – the progressive accumulation of sand, silt, and mud on the harbour floor –
is a chronic operational challenge in coastal ports worldwide (Port Innovators, 2025). At the
harbour entrance specifically, the effects are immediate and operationally significant for the
following reasons.
1. Reduction in Navigable Depth
The most direct consequence of sediment buildup is a shallower channel. Modern cargo ves-
sels require a minimum underkeel clearance to navigate safely without touching the seabed.
When siltation raises the harbour floor, deeper-draught vessels can no longer enter or exit.
The NOAA Ocean Service describes this as the core driver of maintenance dredging: vessels
require a specific water depth to float, and that depth is continuously being eroded by natural
Page 4 of 17
College of Science, Engineering & Technology
⋄
ASSIGNMENT 2
Year Module — 2026
⋄
Module Code: CMT2601
Module Name: Construction Methods
Assignment No.: Assignment 2
Due Date: 2026
Semester: Year Module 2026
Submitted in partial fulfilment of the requirements for Construction Methods (CMT2601)
at the University of South Africa.
,UNISA | CMT2601 Construction Methods – Assignment 2
Question 1: Risk Assessment Before Construction on Large Infrastructure Projects
1.1 Why a Risk Assessment Must Be Conducted Before Starting Construction on Large
Infrastructure Projects
Question: Explain why a risk assessment must be conducted before starting construction
activities on large infrastructure projects such as harbours, railways, or airports. [5 marks]
Large infrastructure projects – harbours, railways, and airports – are some of the most com-
plex undertakings in civil engineering. They involve a combination of heavy equipment, large
workforces, hazardous environments, and considerable financial investment. Before any ground
is broken, a structured risk assessment is not just recommended; it is a professional and legal
obligation (De Mare et al., 2018). The following points explain why.
1. Identifying Hazards Before They Cause Harm
Construction sites at ports and airports expose workers to risks that are not always obvious
at the outset – deep water edges, overhead power lines, unstable ground, and high-volume
machinery often operate in the same space. A risk assessment forces a systematic look at
what could go wrong. Spotting these hazards on paper is far cheaper than dealing with an
injury or fatality on site (Tepeli, 2020). ISO 31000:2018, the international standard on risk
management, requires that risk identification precede all project activities so that mitigation
measures can be built into the construction plan.
2. Legal and Regulatory Compliance
South African law, through the Occupational Health and Safety Act 85 of 1993 and its Con-
struction Regulations, requires contractors to prepare a documented risk assessment before
work begins. Non-compliance exposes the principal contractor and client to criminal liability,
civil claims, and project stoppages. For large state-funded infrastructure – a new harbour ex-
pansion or airport terminal – the consequences of non-compliance can be especially severe, as
regulatory bodies and oversight authorities scrutinise such projects closely.
3. Protecting Workers, the Public, and the Environment
Harbours and airports are operational environments. Construction activity at a functioning
harbour, for instance, happens close to live vessel traffic and active cranes. Without a risk
assessment, the construction team has no structured basis for deciding where to erect barriers,
where to restrict public access, or how to protect sensitive marine ecosystems from construc-
Page 1 of 17
,UNISA | CMT2601 Construction Methods – Assignment 2
tion runoff. The MDPI journal on sustainable civil infrastructure assessment confirms that in-
frastructure projects carry significant environmental and social risks throughout their lifecycle
and that proactive risk evaluation is central to responsible project management (Sustainable
Assessment of Civil Infrastructure Systems, 2022).
4. Financial Planning and Cost Control
Unidentified risks are the leading cause of cost overruns on large civil projects. Gorecki and
Diaz-Madronero (2020) found that qualitative risk analysis on road and motorway projects,
using national risk registers and Monte Carlo simulations, allowed project managers to map
dependent cost variables and prepare more realistic budgets. The same logic applies to har-
bours and airports. A risk assessment lets the project team ring-fence contingency funds for
probable risk events rather than reacting to surprises mid-construction.
5. Informing the Construction Method Statement
A risk assessment directly feeds into the Method Statement – the document that prescribes
how each work activity will be carried out safely. Without the risk assessment, the Method
Statement is incomplete. For a railway construction project, for example, identifying the risk
of track geometry failure under heavy freight loads informs decisions about ballast specifica-
tion, sleeper spacing, and subgrade preparation well before a rail is laid.
Critical Consideration
Under South African law, the Construction Regulations of 2014 (promulgated under
the OHS Act 85 of 1993) make it a criminal offence for a contractor to commence any
construction work without an approved risk assessment and health-and-safety plan.
This requirement is non-negotiable regardless of project size.
Page 2 of 17
,UNISA | CMT2601 Construction Methods – Assignment 2
Question 2: Quay Wall Construction – Site Safety and Harbour Operations
2.1 How Strong Wave Action Affects the Structural Stability of a Quay Wall Under
Construction
Question: Explain how strong wave action can affect the structural stability of a quay wall
under construction. [5 marks]
A quay wall is a gravity or retaining wall structure that simultaneously provides shore pro-
tection and a berthing face for vessels (International Coastal Engineering, 2017). During con-
struction, before the wall has reached its full design mass and before all foundation grouting
and backfill compaction is complete, it is particularly exposed to wave-induced forces. The fol-
lowing mechanisms explain how strong wave action destabilises a quay wall mid-construction.
1. Hydrostatic Pressure Imbalance and Overturning
Every wave cycle exerts alternating positive pressure on the seaward face and negative suction
on withdrawal. On a partially completed caisson or sheet-pile quay wall, this cyclic loading
creates a rocking effect. Research on caisson-type quay walls confirms that the phase relation-
ship between wave action and structural response significantly affects displacement and the
risk of overturning, particularly when the structure has not yet achieved its full dead weight
(Numerical Studies on the Stability of Caisson Quay Walls, Ocean Engineering, 2024).
2. Scour at the Foundation
Wave energy reaching the base of a quay wall during construction can dislodge loose rubble
mound material or erode the seabed substrate beneath the foundation. This is called scour.
When the bearing layer is removed or loosened, the wall can settle unevenly or tilt seaward. A
quay wall still in the process of being seated on its rubble base is especially vulnerable because
the rubble has not yet been consolidated by the full weight of the completed structure.
3. Liquefaction of Saturated Backfill
Backfill placed behind a quay wall during construction is often in a loose, saturated state be-
fore compaction is complete. Repeated wave-induced pressure cycling can cause pore water
pressure to build up in this backfill, temporarily transforming it from a solid-like material into
a fluid-like one. This is soil liquefaction. When the backfill liquefies, the lateral earth pres-
sure on the wall increases dramatically, pushing the wall seaward beyond its design resistance
(Emerald Publishing, Geotechnical Research, 2022).
Page 3 of 17
, UNISA | CMT2601 Construction Methods – Assignment 2
4. Structural Fatigue and Joint Failure
Steel sheet piles, tie-back anchors, and concrete panel joints that are not yet fully installed
are especially susceptible to wave-induced vibration and fatigue. Repeated stress cycles can
open joints, loosen connections, or cause premature cracking in unreinforced concrete sections.
Once a joint fails, water infiltrates the structure, accelerating corrosion and further degrading
structural integrity.
5. Wave Overtopping and Instability of Construction Plant
In rough sea conditions, waves overtopping the wall crest flood the working platform behind
it. This removes any safe operating base for construction equipment, and – more critically
– the added water mass on the landward side changes the load distribution on the partially
completed wall, potentially triggering sliding failure along the foundation plane.
Quality Assurance
Construction of quay walls should be suspended when significant wave height exceeds
the design threshold for the construction stage in use. Site supervisors must monitor
wave forecasts daily and have a documented weather-stoppage protocol that defines the
trigger conditions for evacuating the marine work zone.
2.2 How Sediment Buildup at the Harbour Entrance Affects Harbour Operations and
Vessel Movement
Question: Discuss how sediment buildup at the harbour entrance can affect harbour opera-
tions and vessel movement. [4 marks]
Sedimentation – the progressive accumulation of sand, silt, and mud on the harbour floor –
is a chronic operational challenge in coastal ports worldwide (Port Innovators, 2025). At the
harbour entrance specifically, the effects are immediate and operationally significant for the
following reasons.
1. Reduction in Navigable Depth
The most direct consequence of sediment buildup is a shallower channel. Modern cargo ves-
sels require a minimum underkeel clearance to navigate safely without touching the seabed.
When siltation raises the harbour floor, deeper-draught vessels can no longer enter or exit.
The NOAA Ocean Service describes this as the core driver of maintenance dredging: vessels
require a specific water depth to float, and that depth is continuously being eroded by natural
Page 4 of 17
