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Risk Management Model in Rock Tunnelling Constructions
Teresa Lopes Serra Ramalhão Fortunato
Extended abstract of thesis submitted to obtain the Degree of Master in
Civil Engineering
Jury
President: Prof. Luís Manuel Alves Dias
Supervisor: Prof. Pedro Miguel Dias Vaz Paulo
Vowel: Prof. Fernando António Baptista Branco
January 2013
Risk Management Model in Tunnelling Constructions
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1. Introduction
All companies and organizations regardless of size or industry face in their daily operations
influences both from internal and external factors, which increase the degree of uncertainty
endangering both the objectives and deadlines of their projects. One can therefore define risk as the
effect that the above-mentioned uncertainty has on the company objectives. Nowadays, the
competitive environment in which Civil Engineering companies operate, the technology evolution in
this industry, the economic and legal swings and environmental concerns led these companies to
search for lean processes, new materials and new construction techniques. As such, Risk
Management started to increase in prominence in companies in order to decrease gradually deviations
in objectives derived from risky events.
Henceforth, the following objectives were defined for this Master’s thesis:
The development of a bibliographic research that would allow to understand the main concepts
related with the Risk Management field of study;
To provide a comprehensive study of the fundamental concepts found in the bibliographic
research;
To provide an insight of several Risk Management methodologies such as COSO, PMBOK and
ISO 31000;
The development of a risk evaluation methodology applied to construction engineering;
Applying the proposed methodology to a real case study, evaluating the risks related to a specific
tunnelling construction;
Understanding the limitations and gains of the developed methodology.
2. State of the Art
2.1. Definitions
2.1.1. Defining Risk
The concept of risk in the Civil Engineering sector has been gaining prominence in risk
management studies. Nevertheless, there is not a clear and generally accepted concept of risk in the
academic universe. Due to the endandering factors associated with costs and deadlines overruns and
the consequences of accidents in human lifes, Civil Engineering is within the industries where Risk
Management practices are more developed.
Since the 1970s and 1980s that the concept of risk was either commonly associated with
danger events or alternatively with a beneficial event associated wth uncertainty. The latter is
supported by Akintoye and MacLeod (1997) that argue that the concept of risk has embedded more
than simply the notion of danger or loss.
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The Project Management Institute - PMI (2008) defines risk as an event or uncertain condition,
which if it occurs, would have either a negative or positive effect in at least one objective of the project
such as time, cost or quality.
2.1.2. Defining Constructing Risk
Nowadays, with the cemented awareness of project management practices, they became to
grow in importance in all sectors of industrial activity and particularly to Civil Engineering. Yet, the
application of concepts and procedures drawn by the modern management theories has been
struggling and suffering mutations in order to allow its implementation in the Civil Engineering sector,
mainly due to its specific set of characteristics, nature of production process and specificity of the
market.
According to Mladen Radujkovic (1996), the following risks are the most threatening for the risk
management practice:
Failure to comply with the stipulated budget;
Failure to meet the deadline of the project;
Failure in the quality of the final product.
With the aim of avoiding that the above-mentioned events emerge one should consider studying
the likely impacts of risks in the initial phase of the project. This approach would allow a correct risk
identification and secondly to define strategies to mitigate them. Furthermore, as mentioned in the
PMBOK Guide, while risk is higher in the first phases of a project, it will gradually decrease as time
goes by.
2.1.3. Defining Risk Management
All projects have embedded uncertainty. The main goal of Risk Management is to overcome
the latter uncertainty so as to deal and understand the influence of risks in the project outcome.
Project risks can be interpreted as threats – situation in which one should define mitigation strategies -
or opportunities, case in which controlling risk can boost competitive advantages for a product and
enterprise, with embedded benefits in costs and duration of activities (Estrela, 2008).
During the Risk Management process, although the establishment of the phases is not
unanimous among academic literature, all authors maintain certain coherence. Virtually all authors
divide the process of risk management in three stages: risk identification, analysis and assessment of
risks, identification of alternative actions to promote their treatment.
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2.2. Chronology of Reference Models
The following reference models (table 1) were without a doubt strong drivers for the increase
in awareness and importance gained by risk management practices.
Table 1 – Chronology of reference models
Model Year Description Author
COSO 1992 Framework for implementing a structure of internal controls based on five components: control environment, risk evaluation, control activities, information and communication and monitoring.
Committee of Sponsoring Organizations of the
Treatdway Commission
ERM 2004 Extension of the concept drawn by COSO aligned with the strategy of the organization. Introduced new concepts.
Committee of Sponsoring Organizations of the
Treatdway Commission
PMBOK 2008 Promotes the fundamental concepts of project management and identifies the best practices adjusted to the majority of the projects during its several different phases.
PMI (Project Management Institute) an international non-
profit organization
ISO 31000
2009
World reference for the risk management practice. Presents eleven management principles of risk management i.e. models of orientation for the development and controlling of a risk framework and a generic process of risk management.
ISO –International Organization for Standardization
3. Proposed Methodology for Risk Management
3.1. Methodology Introduction
This section has as objective to develop a methodology that allows guiding construction
companies in implementing a process of identification and evaluation of the potencial risks in their
construction projects. This methodology was developed in order for its application to be performed
individually in each activity of the construction process so as to ensure a detailed and focused study.
Henceforth, it is intentded that the risks identified and evaluated are linked to a specific activity
analysed. Regarding the nature of the activity risk, rather than focusing on its execution the author will
focus its dissertation on a broad but extensive analysis of the activity risk.
The construction of this methodology was performed based on the analysis and study of the
models presented in the previous section. The author will focus its study on the construction phase of
the contract, since it is one of the most important phases of the process. Although the methodology
should be applied to the specific environment of each construction, it can serve as best practices
guidelines for civil engineering companies.
3.2. Methodology Organization
The developed Risk Management methodology can be adapted and implemented in all
activities embedded in the construction process and was drawn based on the following references:
International Standard ISO 31000:2009 (risk management – principles and guidelines)
ISO 73: 2009 Guide (risk management – vocabulary);
IEC/ISO 31010:2009 (risk management – risk assessment techniques);
PMBOK Guide, 2008.
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The implementation of the Risk Management methodology allows identifying, analysing,
mitigating and controlling the risks associated in the construction phase of the specific contract
studied. According with the methodologic guidelines above-mentioned, the proposed methodology will
be drawn based on the phases presented in figure 1.
Figure 1 – Structure of Methodology (ISO 31000:2009).
4. Application of Proposed Methodology: Case Study
The goal of the following section is to assess the adaptability and limitations of the above-
mentioned Risk Management methodology of a real case study of a construction. The construction
selected to apply the methodology has the increase in power generation capacity of Venda Nova III
Dam, in which the author performed an internship. The activity selected to apply a detailed analysis of
risks was the underground tunnelling.
4.1. Environmental Analysis
In this section, a summarized description of the environment in which the following study
occurred is presented, particularly the identification of the location, scope and details of the selected
activity.
4.1.1. Construction Identification
The selected construction is located in the hydroelectric power generation plants of Venda
Nova – Increase in power generation capacity of Venda Nova II (Central de Frades), which is located
in the region Entre o Douro e Minho.
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4.1.2. Identification and Description of the Activity
The objective of this subsection is firstly to identify and describe the selected activity studied in
the real case study and secondly to refer the causes for the decision process. Furthermore, it will also
be descriped the construction process as well as a list of the equipments and materials used in order
to present and summarize the main characteristics and phases of this process.
After analysing both the planning and the technical requirements of the project in order to
select an activity that would represent the complexity of the construction, the chosen activity was the
underground tunnelling activity. This activity is subdivided into the following cyclical sequence (figure
2):
Figure 2 – Division of the underground tunnelling activity into sub activities
4.2. Risk Assessment
4.2.1. Risk Identification
Having performed the analysis of the selected activity and followed in loco the construction works, the
author started to identify the existing risks in each sub activity of the underground tunnelling activity. In
order to obtain an extensive analysis the author used brainstorming techniques, which involved
scheduled meetings and several debates about the potencial risks, its causes and potencial controlling
systems. The list of risks presented in tables 2,3,4,5,6,7 and 18 was obtained by mutual agreement
between all the stakeholders involved.
Table 2 Identification of risks associated with front marking
No. Risk Risk Descprition Stakeholders
1 Disagreements on topographic
meeting tunnels ran on two fronts
Risk of failing to verify the allowable limits in two fronts against a tunnel ran in both
directions.
Planning / Project Technical Office Department
(TOD)
2 Malfunction or damage to
equipment Equipment malfunction by topography (total
station or laser). Construction and Execution / Production Department (PD)
3 Occurrence of work accidents This risk refers only to accidents at work when dialing with the first phase of the
process.
Security Management of Health and
Safety at Work (MHSW)
1
Front Marking
2
Front Drilling
3
Explosives Charging
4
Detonation or Explosion
5
Irrigation and debris removal
6
Advance support
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Table 3 – Identification of risks associated with the front drilling activity
No. Risk Risk Descprition Category / Stakeholders
4 Delays in hiring a specialized
subcontractor
This risk analysis in a generical way the probability and consequences of not hiring subcontractors specialized in front drilling
Construction and Execution / Production Department (PD)
5 Unexpected influx of
groundwater
This risk refers to the possibility of floodwater in greater amounts than anticipated, from the
Hydraulic Circuit of VN II or from the rock mass.
Planning / Project Technical Office Department
(TOD)
6 Malfunction or damage to
equipment Damage to the equipment used during
drilling (jumbo). Construction and Execution /
Production Department (PD)
7 Environmental accidents This risk refers only to environmental
accidents arising from equipment spillage.
Environment / Environmental Management
(EM)
8 Occurrence of work accidents This risk refers only to accidents related to
the front drilling activity.
Security Management of Health and Safety
at Work (MHSW)
Table 4 – Identification of risks associated with the explosives charging activity
No. Risk Risk Descprition Stakeholders
9 Delays in the supply of materials Risk associated with the delay in
delivery / supply of explosives and cords.
Administrative and Financial Administrative and Financial
Department (AFD)
10 Delays in hiring a specialized
subcontractor
This risk can arise from the impossibility of hiring subcontractors specialized in
the application of explosives.
Construction and Execution / Production Department (PD)
11 Occurrence of work accidents This risk refers only to accidents related
to the handling of explosives.
Security Management of Health and
Safety at Work (MHSW)
Table 5 – Identification of risks associated with detonation
No. Risk Risk Descprition Stakeholders
12 Unexpected influx of
groundwater
This risk refers to the possibility of floodwater in greater amounts than
anticipated, from the Hydraulic Circuit of VN II or from the rock mass.
Planning / Project Technical Office Department
(TOD)
13 Transmission of vibrations This risk refers to the possibility of the transmission of vibrations in greater
levels then the established ones.
Planning / Project Technical Office Department
(TOD)
14 Occurrence of other accidents This risk refers only to accidents at work
during the detonation activity.
Security Management of Health and Safety at
Work (MHSW)
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Table 6 – Identification of risks associated with irrigation and debris removal
No. Risk Risk Descprition Stakeholders
15 Malfunction or damage to
equipment
Malfunctions in equipment used during debris removal (mining shovel, loader, front loader
(ITC), trucks and dumpers).
Construction and Execution / Production Department (PD)
16 Occurrence of work accidents This risk refers only to accidents occurred while
removing debris and sanitation.
Security Management of Health and
Safety at Work (MHSW)
Table 7 – Identification of risks associated with advance support.
No. Risk Risk Descprition Stakeholders
17 Changing geological conditions- geotechnical massif in relation to
reference conditions
Changing the zoning of geotechnical massive excavated.
Planning / Project Technical Office Department
(TOD)
18 Underground landslide in the
excavation front
Occurrence of front collapsing while working on the excavation proceeds. Normally due to
lack of support capacity of the land or the release of blocks.
Planning / Project Technical Office Department
(TOD)
19 Malfunction or damage to
equipment Failure of equipment used during the support
for advancement (robot projection and Jumbo)
Construction and Execution / Production
Department (PD)
20 Occurrence of work accidents This risk refers only to accidents caused by
falling rocks, landslides or even the existence of an unsafe piece of stone.
Security Management of Health and
Safety at Work (MHSW)
21 Defects in construction /
manufacturing Deficient construction due to misapplication of
concrete and / or defectuous concreting. Technical Quality
Quality Management (QM)
22 Lack of quality in the manufactured
concrete designed Application of concrete designed with poor
quality. Technical Quality
Quality Management (QM)
23 Embedding of unsuitable materials
Deficient construction by embedding
unsuitable materials, which do not comply with the requirements.
Technical Quality Quality Management (QM)
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Table 8 – Identification of risks commons in all phases
No. Risks Risk Description Stakeholders
24 Delay in delivery of the project by
the project owner
This risk is associated with the delay in timely delivery of the project by the project owner due
to the excavation.
Planning / Project Technical Office Department
(TOD)
25 Delay in the onset of sub-activity Onset of sub activities and consequences that
might ensue.
Construction and Execution / Production
Department (PD)
26
Payment of fines to officials arising from non-compliance with legislation in the area of Health
and Safety at work
Costs arising from the payment of fines relating to breaches of legislation in the area of Health
and Safety at work.
Security Management of Health and
Safety at Work (MHSW)
27 Payment of fines to officials due to non-compliance with legislation in
the area of Environment
Increased costs resulting from the payment of fines in the Environment.
Environment / Environmental Management
(EM)
28 Lack/Failure of Ventilation This risk is associated with damages to the
ventilation system.
Security Management of Health and
Safety at Work (MHSW)
4.2.2. Risk Analysis
As described in the proposed methodology, after identifying the several risks associated with
the activity, each risk was analysed according to its probability of occurence and impact (table 9). This
analysis was performed individually for three variables: cost, deadline and image.
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Table 9 – Risk Analysis
Subatividade Identificação do risco
Subfactors Evaluation
I1 –Cost I2- Deadline I3- Image
Pont. LR Pont. LR Pont. LR
Front Marking
Disagreements on topographic meeting tunnels ran on two fronts
P 1 10
P 1 10
P 1 20
I 10 I 10 I 20
Malfunction or damage to equipment P 1
10 P 1
5 P 1
20 I 10 I 5 I 20
Occurrence of work accidents P 1
5 P 1
5 P 1
2 I 5 I 5 I 2
Front drilling Activity
Delays in hiring a specialized subcontractor P 2
20 P 2
20 P 2
10 I 10 I 10 I 5
Unexpected influx of groundwater
P 2
10
P 2
20
P 2
4 I 5 I 10 I 2
Malfunction or damage to equipment P 2
20 P 2
20 P 2
10 I 10 I 10 I 5
Environmental accidents P 1
5 P 1
2 P 1
10 I 5 I 2 I 10
Occurrence of work accidents P 1
10 P 1
5 P 1
20 I 10 I 5 I 20
Explosives charging activity
Delays in the supply of materials P 2
20 P 2
20 P 2
10 I 10 I 10 I 5
Delays in hiring a specialized subcontractor P 2
20 P 2
20 P 2
10 I 10 I 10 I 5
Occurrence of work accidents P 2
20 P 2
20 P 2
40 I 10 I 10 I 20
Detonation
Unexpected influx of groundwater P 2
10 P 2
20 P 2
4 I 5 I 10 I 2
Transmission of vibrations P 2
10 P 2
4 P 2
4 I 5 I 2 I 2
Occurrence of other accidents P 2 40
P 2 20
P 2 40
I 20 I 10 I 20
Irrigation and debris removal
Malfunction or damage to equipment P 1
10 P 1
10 P 1
10 I 10 I 10 I 10
Occurrence of work accidents P 1
5 P 1
5 P 1
5 I 5 I 5 I 5
Advance Support
Changing geological conditions- geotechnical massif in relation to reference conditions
P 3 15
P 3 15
P 3 6
I 5 I 5 I 2
Underground landslide in the excavation front P 2
20 P 2
10 P 2
40 I 10 I 5 I 20
Malfunction or damage to equipment P 2
10 P 2
10 P 2
20 I 5 I 5 I 10
Occurrence of work accidents P 1
5 P 1
5 P 1
20 I 5 I 5 I 20
Defects in construction / manufacturing P 1
20 P 1
20 P 1
20 I 20 I 20 I 20
Lack of quality in the manufactured concrete designed
P 1 20
P 1 20
P 1 20
I 20 I 20 I 20
Embedding of unsuitable materials P 1
20 P 1
20 P 1
20 I 20 I 20 I 20
Common Risks
Delay in delivery of the project by the project owner
P 2 10
P 2 40
P 2 20
I 5 I 20 I 10
Delay in the onset of sub-activity P 2
10 P 2
20 P 2
20 I 5 I 10 I 10
Payment of fines to officials arising from non-compliance with legislation in the area of Health and Safety at work
P 1
20
P 1
2
P 1
20 I 20 I 2 I 20
Payment of fines to officials due to non-compliance with legislation in the area of Environment
P 1
20
P 1
2
P 1
20 I 20 I 2 I 20
Lack/Failure of ventilation P 2
10 P 2
20 P 2
4 I 5 I 10 I 2
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4.2.3. Risk Evaluation
The last phase in the risk assessment process is the risk evaluation. This evaluation was
performed individually for each risk, using the risk matrix methodology that bases its approach on
computing the average of the numerical analysis of the three individual variables in order to obtain a
final quantitiative proxy for the level of risk, using the following formula:
Level of Risk = Probability (p) × Impact (I)
This methodology considers that the three subfactors – cost, deadline and image – have the
same weight for computing the level of risk. Henceforth, the level of risk is computed using a simple
average of the numerical values of each subfactor:
Table 10 presents the final evaluation of the risks present in the underground tunnelling
activity per sub activity.
No. Risk LR No. Risk LR No. Risk LR
1
Disagreements on topographic meeting tunnels ran on two
fronts
13 10 Delays in hiring a
specialized subcontractor
27 19 Malfunction or
damage to equipment
13
2 Malfunction or
damage to equipment 12 11
Occurrence of work accidents
27 20 Occurrence of work
accidents 10
3 Occurrence of work
accidents 4 12
Unexpected influx of groundwater
11 21 Defects in
construction / manufacturing
20
4 Delays in hiring a
specialized subcontractor
13 13 Transmission of
vibrations 6 22
Lack of quality in the manufactured
concrete designed 20
5 Unexpected influx of
groundwater
11 14 Occurrence of other
accidents 33 23
Embedding of unsuitable materials
20
6 Malfunction or
damage to equipment 17 15
Malfunction or damage to equipment
10 24 Delay in delivery of the project by the
project owner 23
7 Environmental
accidents 6 16
Occurrence of work accidents
5 25 Delay in the onset of
sub-activity 17
8 Occurrence of work
accidents 12 17
Changing geological conditions-
geotechnical massif in relation to
reference conditions
12 26
Payment of fines to officials arising from non-compliance with
legislation in the area of Health and
Safety at work
14
9 Delays in the supply
of materials 17 18
Underground landslide in the excavation front
23 27
Payment of fines to officials due to non-
compliance with legislation in the
area of Environment
14
28
Lack/Failure of Ventilation
11
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Figure 3 presents the evaluation of the final risks considered in the matrix of risks.
Impact
Pro
ba
bil
ity
Figure 3 – Representation of the risks associated with the underground tunnelling activity
4.3.4. Plan of Action
According to the defined methodology, the risks that require a plan of action in order to
mitigate them to acceptable levels are the ones that have a level of risk such as 15≤LR<25. The risks
that have 25≤NR<50 require an immediate plan of action and treatment (table 11).
Tabela 11 – Risks that require a plan of action
Classification No. and Risk description Proposed Plan of Action
25≤LR<50
Nº 11 - Occurrence of work accidents Nº 14 - Occurrence of accidents
So that the level of risk decreases to acceptable values one should: - Revise the processes, procedures and existent controls; - Implemented new control measures.
15≤LR<25
Nº 4 - Delays in hiring a specialized subcontractor Nº6 - Malfunction or damage to equipment Nº 9 - Delays in the supply of materials Nº 10 - Delays in hiring a specialized subcontractor Nº18 - Underground landslide in the excavation front Nº21 - Defects in construction / manufacturing Nº 22 - Lack of quality in the manufactured concrete designed Nº23- Embedding of unsuitable materials Nº 24 - Delay in delivery of the project by the project owner. Nº25- Delay in the onset of sub-activity
1
4
10
2 3
5 9
7 8
6
11
12
13
14
15
16
17
18
20
21
19
22
23
24
25
26 27
28
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5. Analysis of Results
As described in the proposed Risk Management methodology presented in section 2, the Risk
Management process should be monitorized and controlled regularly so as new risks are identified or
removed. In this dissertation, this topic was not developed due to the scope of the study, directed
towards a specific activity. Therefore and having into account that there are no records of this type in
the construction being studied it is not possible to perform a comparative analysis that would allow the
author to understand the real gains of the creation of the proposed Risk Management methodology.
Henceforth, the author opted to perform a final analysis of results based on the statistical study of the
occurrence of the indentified risks.
In the risk identification and evaluation phase, seven construction employees and more
particularly the stakeholders defined as the main responsibles for Risk Management practices aided
the author. To robust the validity of the model and reliability of results data related to the education
and experience of such employees was collected.
Such intervinients were questioned about their education and years of experience in the
industry and if they had experience with underground tunnelling activities. Regarding their professional
experience, none of them possessed less than five years of professional experience, factor that
helped both the identification and analysis of risks but more importantly the technical requirments of
the construction. Finally, all the participants presented significant experience in underground tunnelling
constructions.
Throughout the analysis performed it is possible to verify that the sub activities that present
the higher number of risks are: front drilling and advance support. However the sub activities that
present higher levels of risk are explosives charging and detonation.
Therefore, the author recommends the monitoring of all the underground tunnelling process.
Figure 4 – Graph representative of the risks associated with the underground tunnelling activity
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Broadly speaking the underground tunnelling activity presents twenty-eight identified risks
(figure 4) subdivided by sub activities. One can conclude that the majority of these risks have an
acceptable level. The major factors that contribute for for this classification are related with the several
internal controls systematized in the construction plant such as maintenance plans, equipment
controls, training, material inspection, high level of experience of the team members but also due to
the high standards imposed by the constractor.
It is important to state that since the author divided the activities into subactvities, in the
process of risk identification one was able to increase the scope of the found risks and to perform an
adequate evaluation in each phase of the activity.
Figure 5 allow us to evaluate that for the three risks common to all activity phases, depending
on the phase of the project, they posess diferent levels of risk. Henceforth, analysing the graph it is
possible to state that the level of risk (LR) mutates with the phases of the project. It is easy to
understand this phenomenon if we think that the level of risk varies with its probability of occurrence
and indirectly with the existing controlling measures. Different sub activities have implied different
probability of occurrence and controlling measures.
Figure 5 – Graph representing the number and level of risks that are common to more than one phase
The risk of malfunctions in equipments was identified in four phases. Regarding this risk, its
level was higher in the front drilling phase due to the fact that the Jumbo it is sensible equipment, with
frequent breakdowns with slow repairing. By the contrary, the same risk in phase 5 - irrigation and
debris removal – presents the lowest level of risk since removal trucks are easily substituted. The risk
of accident occurrence presents its higher level in the detonation phase, since in this phase the
Risk Management Model in Tunnelling Constructions
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possibility of being fatal to the participants is higher and consequently it will have higher impact
although its inherent probability is low.
The lowest value is related with the front marking activity mainly due to the fact that this
activity does not require lot of employees and due to the several topography equipments available
which indirectly decreases the probabibly of accident occurance but also its impact. The risk related
with the delay in hiring specialized subcontractors influences both the front drilling and the explosives
charging phases, which are the two phases, composed by subcontracts. The level of risk is similar in
these two sub activities.
The attitude towards this method should not be passive. Such approach would be completely
inadequate regarding the fundamental principles of risk management since each project must be
analysed individually. One should decide, based on the obtained values, if each activity or sub activity
should progress or not.
6. Conclusions and Future Studies
The choice of the topic studied in this dissertation was motivated by the increasing importance
of Risk Management practices in the Civil Engineering sector, having as main goal to underline paths
that allow companies to assess and mitigate risks associated with their projects. The methodology
created by the author had as main objective to present the Risk Management process in its several
phases – identification, evaluation and plan of action – the key variables in each sub activity such as
cost, deadline and image and finally to be flexible to be applied to other construction structures using
as basis the International Standard ISO 31000:2009 and the PMBOK Guide.
Although in the academic world there are doubts about the flexibility of readapting the above-
mentioned methodologies for other real case studies, the proposed methodology is validated in this
thesis and can be considered without a doubt superior to the ISO 31000:2009 ancestor models
particularly when it comes to criteria such as consistency, reliability and maturity of the results.
Regarding future studies in this area the author would like to mention the importance of implying, in a
continuous way, the proposed methodology in several distinct activities in order to ascertain its
practical adaptability.
Furthermore the author suggests the creation of a database composed by the results obtained
for the several level of risks associated with each activity in order to aid future similar construction real
case studies.
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7. Bibliography & References
Akintoye, A.S. & MacLeod, M.J. (1997). Risk analysis and management in construction. International Journal of Project Management, 15(1), 31-38. Committee of Sponsoring Organizations of the Treadway Commission (COSO). (2004). Enterprise Risk Management – Integrated Framework. Executive Summary. USA. Estrela, Miguel Paulo Medeiros Vieira. (2008). Metodologia de Análise e Controlo de Risco dos Prazos em Projecto de Construção. Thesis (Masters in Civil Engineering) – Instituto Superior Técnico – IST, Lisboa. Frame, D. (2003). Managing Risk in Organizations. The Jossey-Bass Business & Management Series, Wiley. ISO (International Organization for Standardization). (2009). ISO 31010 - Risk management – Risk assessment techniques. 93, Switzerland. Project Management Institute (PMI). (2008). Project Management Body of Knowledge (PMBOK Guide). (4ª ed.). Editora PMI.
Radujkovic, Mladen. (1998). Modelling cash flow in construction projects in countries in transition. Faculty of Civil Engineering. University of Zagreb. Zagreb, Croatia.