Teknik Dergi, 2020 10085-10111, Paper 581

Geotechnical Risk Identification: Case Study of

Flexible Retaining Wall Installation*

Danute SLIZYTE1
Natalija LEPKOVA2
Rimantas MACKEVICIUS3

ABSTRACT
Analysis of the scientific literature has demonstrated that the risk of collapse or deformations
of flexible retaining walls has not been the object of in-depth examination so far. The article
presents an analysis of the main geotechnical risks, focusing on the installation of flexible
retaining walls according to analysis by construction participants and their experiences. A
case study was conducted to identify the risks of flexible retaining walls. In order to
determine the risks of installation of flexible retaining walls, the authors of the article
employed a face-to-face interview approach. Investigation of the data obtained during the
face-to-face interview was based on brainstorming and the cause and effect diagram: five
professionals who had monitored most of the risks were selected with the help of the face-
to-face interview. The results of the investigation showed, that for specific and complicated
projects the team of professionals should be composed of specialists from different fields of
construction. Additionally, the respondents agreed with the opinion that the greatest loss in
the given situation would be caused by a breakdown in the pressure pipe and pollution of the
natural environment by wastewater. The novelty of the article on investigating the
possibilities for identifying the risk of installation of flexible retaining walls and on
suggesting risk identification steps.
Keywords: Flexible retaining wall, technical risk, cause and effect diagram.

Note:
- This paper has been received on September 12, 2018 and accepted for publication by the Editorial
Board on April 24, 2019.
- Discussions on this paper will be accepted by September 30, 2020.
 https://dx.doi.org/10.18400/tekderg.459316

1 Department of Reinforced Concrete Structures and Geotechnics, Vilnius Gediminas Technical University,
Vilnius, Lithuania -danute.slizyte@vgtu.lt- https://orcid.org/0000-0002-1220-7485
2 Department of Construction Management and Real Estate, Vilnius Gediminas Technical University,
Vilnius, Lithuania - natalija.lepkova@vgtu.lt - https://orcid.org/0000-0002-9760-1747
3 Department of Reinforced Concrete Structures and Geotechnics, Vilnius Gediminas Technical University,
Vilnius, Lithuania - rimantas.mackevicius@vgtu.lt -https://orcid.org/0000-0002-5643-1147
Geotechnical Risk Identification: Case Study of Flexible Retaining Walls Installation

1. INTRODUCTION
The article analyzes risk identification when installing flexible retaining walls. The article
considers this problem, taking into account that not all risks are always assessed within the
process of installing flexible retaining walls, which may result in collapse or deformations.
To determine and analyze risk, the concept has to be defined. Risk considers the probability
of an event occurring and the consequences of the event, should it occur [1]. Emerging risk
can be defined as the likelihood of loss, that is, the probability that a certain consequence will
occur in a specific time and space under specified or insufficiently specified conditions [2].
This article adopts the definition of risk as the ‘effect of uncertainties on objectives’ given
by ISO 31000:2009 [3]. The definition provides that uncertainties include events (that may
or may not happen) and are caused by ambiguity or lack of information. It also includes both
negative and positive impacts on objectives [3]. The article reports only negative effects.
Geotechnical risk has been analyzed in a number of scientific articles. Duncan [4]
investigated safety and reliability in geotechnical engineering. Special attention was paid to
uncertainty about the factors involved in safety against sliding. As an example, the stability
of a cantilever retaining wall with silty sand backfill was analysed. Gibson [5] explored and
compared four probabilistic methods for slope analysis and design. Brown [6] reviewed risk
assessment and management practice in underground rock engineering. Swannell et al. [7]
analysed the geotechnical risk management approach to boring machines tunnelling under
squeezing ground conditions. Lacasse [1] showed how the concepts of hazard, risk, and
reliability could help with making more secure decisions. The article shows examples of
calculation taken from a wide range of geotechnical problems, including the hazard and risk
of collapse related to railway traffic, mine slopes, and soil exploration. Mishra et al. [8]
analysed tools for geotechnical real-time risk assessment and management and proposed a
geotechnical risk management workflow diagram of intelligent deep mines. Xia et al. [9]
focused on the issue of model uncertainty and differences in risk consciousness with different
decision-makers in tunnel and underground engineering and proposed a risk decision model
based on sensitivity analysis and tolerance cost, which can improve decision-making
efficiency. Haddad et al. [10] performed a study based on the failure and stability of gravity
retaining walls, which can be categorized into three different modes of failure in sliding,
overturning, and foundation-bearing capacity. They introduced a relatively simple method of
probabilistic analysis of the dimensions of gravity retaining walls which might lead to a more
accurate understanding of failure. Risk management in the architecture, engineering, and
construction industries remains a global issue. Lack of adequate risk management may cause
difficulties in implementing the objectives of a project and negatively affect spatial planning
and urban spatial design in the future. Yang et al. [11] analysed risk management in the field
of health and safety using Building Information Modelling (BIM) and other BIM-related
technologies. Li et al. [12] analysed site selection for underground petroleum storage. To
reduce construction risk and cost during the construction of underground petroleum storage,
they proposed a new site selection model for large underground petroleum storage based on
the analytic hierarchy process (AHP) method and ideal point theory. Xue at al. [13] analysed
rockburst hazard, which is an important issue affecting safe production at coal mines in
China. They paid attention to the influence of the backfilling roadway driving sequence on
coal pillar stability. Ahmasi et al. [14] presented a comprehensive framework to manage the
main risk events of highway construction projects within three stages: (1) identification of

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potential risks; (2) assessment and prioritization of identified risks based on fuzzy FMEA;
(3) identification of appropriate response. Authors suggested the new expert system for
identifying an appropriate risk response strategy for a risk event based on risk factor, control
number and risk allocation. The proposed methodology is demonstrated for management of
risk events in a construction project of Bijar-Zanjan highway in Iran. Valipour et al. [15]
applied hybrid SWARA (Step-wise Weight Assessment Ratio Analysis) -COPRAS
(COmplexPRoportionalASsessment) method for risk assessment in deep foundation
excavation project through introducing new criteria for risk assessment. A case study of deep
foundation excavation in Shiraz (Iran) was presented. The results have shown that the risks
involving construction safety, unfavourable geological conditions, shortage of managerial
experience, incomplete emergency plan and subsidence of ground are the most significant
risks excavation projects in Shiraz.
To sum up, the risk of collapse or deformations of flexible retaining walls has not been widely
examined.
This paper aims to identify the most common risks of installing flexible retaining walls. The
analysis performed involves the face-to-face interview approach, brainstorming, and a cause
and effect diagram. The article discusses a specific case of installing flexible retaining walls.
This case study has been selected with reference to the results of the face-to-face interviews,
showing that the parties involved in construction most frequently fail to assess the risk of
installing the flexible retaining wall, which causes some problems in geotechnical
applications in Lithuania. Identification of risks is important for risk analysis in order to
reduce the number of emergencies. The face-to-face interview approach and the
brainstorming method were chosen for analysis, as the knowledge and experience of experts
in the field of installing flexible retaining walls allow a more thorough identification of
possible risks. The major finding of the face-to-face interview approach was that the greatest
loss is caused by breakdown in the pressure pipe. When analysing the case of installing the
flexible retaining wall using the cause and effect diagram, all possible risks leading to the
breakdown in the pipe are shown graphically.
The novelty of this article is investigating the identification of possible risks when installing
flexible retaining walls and suggests risk identification steps in the risk management flow of
the flexible retaining wall installation process.
The structure of the article is built as follows. Section 2 analyses geotechnical risks. The
authors of the article present the case study and risk identification by applying the face-to-
face interview approach in Section 3. Having analysed the data obtained during the face-to-
face interview and clarifying the possible causes of breakdown in the pipe, brainstorming and
the cause and effect diagram were used. Section 4 deals with risk identification in the risk
management flow of the flexible retaining wall.

2. GEOTECHNICAL RISK IDENTIFICATION

Risk identification is very important in the risk management cycle. Once the risk has been
identified, a decision has to be made regarding whether to take the risk if it is acceptable or
to make some changes to reduce it if it is unacceptable.

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Geotechnical Risk Identification: Case Study of Flexible Retaining Walls Installation

To identify risk, the Swedish Geotechnical Society (SGF) [16] recommends employing
methods for detecting hazards and considering possibilities. When opting for techniques and
organizing a risk management team, one has to adhere to the following principles:
Risk identification is considered to be an engineering task:
 anyone who may be of benefit to the work should be engaged in it;
 the goals of the project have to be considered first;
 a unified approach should prevail, and therefore all aspects of the project have to be
studied;
 necessary information should be collected;
 both hazards and consequences have to be investigated and distinguished from each other;
 risk should be analysed without emotions;
 there should be concentration on risk rather than on solving related problems.
The result should be documented so that it can be used for the entire project.
The geotechnical risk of the project is a part of the risk of a construction project and is
frequently one of the most controversial parts of the technical risks. ‘Geotechnical risk – is
the risk to buildings and construction work created by the site ground conditions’ [17].
However, this is only one of many risks that are specific to geotechnical projects. Table 1
presents the specific risks and hazards of geotechnical projects. In general understanding, a
hazard is something that can cause harm, e.g. electricity, chemicals, working up a ladder,
noise, stress, etc. A risk is the chance, high or low, that any hazard will actually cause
somebody harm. The geotechnical hazard can be named as building collapse, landslides and
etc.

Table 1 - Specific risks and hazards of geotechnical projects (adapted by authors from
Baynes’ [18]).
Type of geotechnical risk Hazard
Project management Poor management of the entire geotechnical process
Poor management of site investigation and contractor
Contractual
documentation
Unreasonable analytical model selected
Nonconformity of the structural scheme with design drawings
Analytical
Nonconformity of the structural scheme with construction stages;
technological effects are not assessed
Technical Properties Unreasonable design values selected
Inherently hazardous ground conditions
Geological
Unforeseen ground conditions
Invalid construction type selected
Construction
Invalid technology selected

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 Danute SLIZYTE, Natalija LEPKOVA, Rimantas MACKEVICIUS

Based on the experience gained in the field of designing and constructing geotechnical
objects, the authors of the article propose five categories for analysing geotechnical risks, as
depicted in Figure 1: water, soil, seismology, surrounding buildings and structures, and
technological processes used during construction.
The first three types of risks are natural and most uncertain.
The risk of breakdown of the structure(Figure 1) took into account geotechnical research,
design, and Eurocodes and standards for specific geotechnical works.
The analysis of water level and its variations in terms of time shows that the groundwater
level is not constant in nature and is subject to various factors such as seasonal changes,
floods, tides, and so on. Frequently, the maximum possible rise in groundwater is calculated
according to standardized diagrams that may not meet local conditions.
External
geotechnical risks

Technological processes Surrounding

Water Seismology Soil
during construction buildings and
structures
Water effect Soil Sensitivity of
Water levels Aggressiveness soil properties Layers
on soil properties Location
properties to destruction considering a Condition
During designed building
Mechanical
investigation
Deformations
In the plan
During
Physical
construction Structural
In the resistance
During section
operation

Figure 1 - External geotechnical risks

The following variations in water level may occur during construction:

 blocking the natural flow of water will result in a rise;
 the water flow may be artificially decreased if it interferes with construction processes.
Variations in soil moisture change the physical and mechanical properties of the soil more or
less, which has a direct impact on the foundation works.
The soil is a naturally occurring dispersion substance whose properties are subject to the
processes and conditions of formation, conditions of the study, and variations in those
conditions. During testing, the mechanical and physical properties of the soil are determined
by employing field (in situ) and laboratory methods. However, it should be noted that the test
results largely depend on the qualifications and diligence of the staff involved in the
investigation. Any inaccuracies in taking, transporting, preparing, and testing a specimen
under laboratory conditions may cause serious distortion of the results. Thus, geotechnical
studies often use accumulated information about the properties of similar soils and compare
the findings with the results obtained. When in doubt, such results should be verified by
additional testing. Attention should be drawn to the fact that soil properties are determined

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Geotechnical Risk Identification: Case Study of Flexible Retaining Walls Installation

only at separate points of the soil matter. Hence, it is important that attention is paid to the
selection of representative specimens when describing the characteristics of a single layer.
Variations in the characteristics of soil exposed to the effects of cold or mechanical or
dynamic factors are accepted as one of the soil properties. Therefore, soil properties described
-in the geotechnical report can only be applied on the condition that the structure of the soil
will not be destroyed during construction and afterwards.
Soil characteristics appear to be one of the greatest sources of risk (see Table 2). Information
on the layout of soil layers during engineering geological explorations and the preparation of
a geotechnical report is limited. The placement of layers is directly investigated in separate
places in the construction site by drilling, and information can be indirectly obtained through
the Cone Penetration Test (CPT), Standard Penetration Test (SPT), or other methods. Only
at tested points are the soil boundaries and type known. Between the tested points, only
assumptions can be made. Therefore, only at the time of construction, when excavating the
foundation pit, is it possible to verify whether the soil and the depth of the soil conform to
the geotechnical report.

Table 2 - Sources of foundation-related risk in construction [17].

Risks related to %
Soil boundaries 22
Soil properties 20
Groundwater 13
Contamination 11
Obstructions 10
Site investigation 9
Services 6
Detailed design 5
Other 4

The seismic effect on the specific construction site cannot be measured. This is the most
uncertain geotechnical external effect. Designing seismic districts is one of the greatest risks,
and the assessment of these risks may lead to fundamental changes in geotechnical solutions.
This effect is strictly regulated by separate normative standards.
For the rest of the risks related to the environment, the size of uncertainties greatly depends
on the ability to collect information about the surrounding buildings and structures. Those
opportunities will certainly be better if the builder's relations with neighbours are good and
if the builder convinces them that the risk to their property will be reduced during
construction by the provision of such information. In this case, there is a need for effective
communication with neighbours in order to avoid frightening them about possible risks. Lack
of communication is due to the fact that everyone treats risk differently [19].

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 Danute SLIZYTE, Natalija LEPKOVA, Rimantas MACKEVICIUS

The selected technological processes of construction can determine the level of risks. From
a geotechnical point of view, efficient technological processes can increase risks on the
construction site. For example, hammering or vibrating a sheet pile wall results in producing
dynamic effects that will lead to the occurrence of thixotropic processes, the soil will
dissolve, and the surrounding structures may lose their foundations in silty sand saturated
with water. Therefore, at the engineering feasibility stage, one of the essential tasks is to
select the most appropriate technological processes taking into account the risks involved.
The risks of the construction project have to be assessed at all stages of its development. Each
of these stages addresses different problems of risk manageability [20]. Figure 2 shows a
diagram describing the risks under consideration during the stages of developing a
geotechnical project. Risk identification and analysis is a continuous process, because each
of the steps may result in additional data that will reveal new risks. The earlier the risk is
identified, the easier its management will be.
To solve geotechnical problems, as the first step, the designer has to collect as much
information as possible about the site itself and about the immediate environment that can
affect the building being designed. This will allow potential risks to be assessed at the initial
stages of the project (planning stage and engineering feasibility stage). Based on the analysis
of the initial information, the project manager will also be able to decide on the extent of the
required geotechnical exploration for the planned facility.

Stage Content

Planning Stage Identification of potential extremely high risk

Manageability of Risk

Engineering Comparison of the risk for different schemes in

Feasibility Stage terms of designs and construction methods

Detailed Design Identification of high risk for selected project

Stage scheme; Establishment of pre-warning measures

Construction
Dynamic risk management during construction
Stage

Operation
Risk management in operating environment
Stage

Figure 2 - Scheme for lifetime risk assessment by Huang and Zhang [20].

In different Member States of the European Union, investigation volumes are subject to the
geotechnical category assigned to the object. This can be done using the process shown in
Figure 3.
Subject to the category, the investigation volume and methods are regulated. A few
geotechnical categories may form the object, which will depend on conditions for variations
in the site and design constructions. It should also be considered that the situation must be
monitored to determine whether there is a need to adjust the established geotechnical
category during the whole construction process [22].

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Geotechnical Risk Identification: Case Study of Flexible Retaining Walls Installation

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However, even following recommendations can reveal some uncertainties. As a rule, for the
objects of the second and third geotechnical categories, the mechanical properties of the soil
are determined by laboratory tests. For example, in determining the indicators of the shear
strength of the soil, their magnitude is subject to available comparable experience (see Table
3), according to EN 1997-2 [23]. Yet documents do not provide information on the type of
comparable experience.

Table 3 - Direct shear test. The recommended minimum number of tests for one soil stratum
[23].
Recommended number of testsa
Variability in strength envelope Comparable experience
Coefficient of correlation on regression curve None Medium Extensive
Coefficient of correlation < 0.95 4 3 2
0.95 ≤ coefficient of correlation < 0.98 3 2 2
Coefficient of correlation ≥ 0.98 2 2 1b
a One recommended test means a set of three individual specimens tested at different normal
stresses.
b A single test and classification tests to verify compatibility with comparable experience. If the

test results do not agree with the existing data, additional tests should be run.

To identify geotechnical risk, specific geotechnical issues that are not always successfully
solved by referring to regulatory documents about this particular field of construction need

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 Danute SLIZYTE, Natalija LEPKOVA, Rimantas MACKEVICIUS

to be considered. Extensive experience of the parties involved in construction has to be taken

into account. Thus, Chapter 3 applies the face-to-face interview approach followed by the
construction participants analysing a certain case study and identifying the main problems
using a cause and effect diagram.

3. RISK IDENTIFICATION APPLYING THE FACE-TO-FACE INTERVIEW

APPROACH
3.1. Data Collection
The authors of this article mainly focus on identifying risks arising from the installation of a
flexible retaining wall. Thus, to achieve this goal, the face-to-face interview approach, which
is one of the methods recommended by ISO / IEC 31010: 2009 [24] was preferred, based on
the argument that it has a lower non-response rate than other methods of surveying.
Furthermore, compared to other cases, the questioning technique enhances the opportunity
to obtain more information and reduces the amount of time required to obtain the information.
The face-to-face interview approach, being flexible, allows data collection using strictly
structured to unstructured questions and very short to long answers [25].
The authors of this article conducted face-to-face interviews of 14 respondents with no time
limit; each interview lasted approximately 30–50 minutes. All of the interviews were
administered by the same person, who had 22 years of work experience in the field of
designing geotechnical structures.
The types of experiences of the respondents and length of experience in their present
positions and in total are listed in Table 4, below.

Table 4 - The demographics of the participants

Experience in the Experience in
Respondent Type of Professional Experience present position total
(years) (years)
1 Associate Professor 37 37
2 Associate Professor 8 12
3 Architect 5 13
4 Geotechnical Designer 7 17
5 Geotechnical Designer 3 3
6 Geotechnical Designer 10 10
7 Geotechnical Expert 24 40
Structural Designer – Structural
8 15 20
Project Manager (SPM)
Structural Designer – Structural
9 4 13
Project Manager (SPM)

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Geotechnical Risk Identification: Case Study of Flexible Retaining Walls Installation

Table 4 - The demographics of the participants (continue)

Experience in the Experience in
Respondent Type of Professional Experience present position total
(years) (years)
Structural Designer – Structural
10 10 19
Project Manager (SPM)
Structural Designer – Structural
11 1 16
Project Manager (SPM)
Structural Designer – Structural
12 8 9
Project Manager (SPM)
13 Expert in Maintenance 8 12
14 Construction Manager 15 25

The interviewees were asked to list the types of geotechnical structures they designed based
on the frequency and level of contribution of their experience.
In response to this enquiry, the top three types of geotechnical structures designed were
revealed to be pile foundations (30%), retaining walls (26%), and shallow foundations (23%).
The distribution of the geotechnical structures designed by the respondents is as depicted in
Figure 4.

6; 8%
5; 6%
1; 23%
4; 7%

3; 26%
2; 30%

Figure 4 - Geotechnical structures most frequently designed by the respondents:

1 - shallow foundations; 2 - pile foundations; 3 - retaining walls; 4 - excavations, slopes,
dikes; 5 - anchors; 6 - other types of geotechnical structures (floor, foundation
underpinning, roads, collectors).

As can be seen from Figure 4, the most commonly used structure is pile foundations and the
second choice is retaining walls.
The most commonly encountered problems identified by the respondents were related to
retaining walls, loose soil, and water. However, very often, respondents related these
problems to insufficient geological exploration, limited information about surrounding
structures and engineering infrastructure, and their assessment at all stages of construction.

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 Danute SLIZYTE, Natalija LEPKOVA, Rimantas MACKEVICIUS

It is worth noting that underground barriers were mentioned as problems only by geotechnical
engineers. The frequency of problems encountered in geotechnical structures as reported by
the respondents is given in Figure 5.

4; 11% 5; 9% 6; 5%
7; 4%
8; 4%
3; 15%

Other; 10% 9; 2%

10; 2%
2; 22%
11; 2%
1; 24%

Figure 5 - Frequency of problems encountered related to:

1 - retaining walls; 2 - loose soil; 3 - water; 4 - limited information about surrounding
structures and engineering networks; 5 - small number ground test; 6 - shallow
foundations; 7 - foundation underpinning; 8 - dynamic loading; 9 - underground barriers;
10 - interaction between geotechnical and overhead structures; 11 - overall stability.

When answering the questions about quality mismatches specific to geotechnical structures
and the usual reasons for their occurrence, 10 out of 14 respondents identified quality
mismatch as a deviation inherent in geotechnical structures. Others mentioned sediment,
insecure reinforcement in the project, insufficient depth, inadequate waterproofing, and
concrete works.
The most significant reason for the appearance of poor-quality geotechnical structures,
according to the respondents, was the geological conditions and their poor assessment or
insufficient geological explorations. Workplace culture on the construction site and errors in
design took second position. Errors in design were often (two times out of four) related to the
inadequacies of technological processes with computational schemes. Also, tight work
deadlines, incorrectly applied technology, misunderstandings, and corruption were also
pointed out. The reasons for poor quality of the finished work and their respective weights
are shown in Figure 6.
Insufficiency of geological and engineering investigations was cited as the most common
cause of poor-quality work. Therefore, an additional enquiry was carried out with the aim of
determining the causes of and reasons for complementary investigations in the design and
construction stages. Only 11 of 14 interviewees responded to this line of enquiry: three
respondents carried out the exploration when the properties of the soil at the site at the time
of construction did not match the data provided in the report; six respondents did so when
they lacked data in the design stage (insufficient depth of exploration, unspecified mechanical
properties of the soil, filtration coefficient, etc.); two of them commissioned additional
studies to clarify the characteristics of the loose soil for a reliable and cost effective design
(Figure 7).

10095
Geotechnical Risk Identification: Case Study of Flexible Retaining Walls Installation

7
6

Number of responses
5
4
3
2
1
0
1 2 3 4 5 6 7
The main reasons

Figure 6 - The main reasons for low-quality geotechnical structures:

1 - workplace culture; 2 - geological conditions or poor evaluation of geological
conditions; 3 - busy work schedules; 4 - incorrect application of technology; 5 - errors in
design; 6 - misunderstandings; 7 - corruption.

7
Number of responses

6
5
4
3
2
1
0
Non-compliance Lack of data in Spread of a loose
with natural soil the project soil

Figure 7 - Reasons for conducting additional geological and engineering investigations.

9
8
Number of responses

7
6
5
4
3
2
1
0
5 4 3 2 1 Others
Assessment
Related companies Non-related companies

Figure 8 - Confidence in the experts

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 Danute SLIZYTE, Natalija LEPKOVA, Rimantas MACKEVICIUS

Geotechnical experts are frequently invited to participate at all stages of construction;

however, the effectiveness of these sessions depends on the mutual trust between
construction participants. Thus, the respondents were asked to assess their confidence in the
experts, specifically confidence in experts from related companies and those from unrelated
companies, that is, outsiders. Respondents were asked to rank their confidence levels using
a 1 to 5 scale where 1 means ‘no trust at all’ and 5 means ‘trust blindly and do not check the
statements made’. The outcome of this enquiry is shown in Figure 8.
All respondents felt more confident when experts were independent, because they could more
objectively assess the situation without ‘linking’ their opinions to a particular solution or the
solutions of a particular company.
As ‘other’ answers, two options were distinguished:
 in the first option, regardless of the considered issue being discussed with the expert
company, the experts were evaluated on an individual basis from 1 to 4 subject to the
company and the designer;
 the second option was related to the companies: 1 to 3 (depending on the situation whether
a decision or requests made by the expert have an effect on the selection of a geotechnical
company and a certain type of foundation).
The provided answers suggest (see Figure 8) that extreme degrees of confidence in experts
are rare: total mistrust never occurred and absolute confidence was a rare occurrence.

3.2. Geotechnical Risks of Installing Flexible Retaining Walls–Case Study

This section analyses the geotechnical risks of installing flexible retaining walls. Flexible
retaining walls started to be applied in residential construction in Lithuania approximately 20
years ago. This was due to growing demand for the creation of underground parking space
in developed urban areas. Therefore, it is no coincidence that the flexible retaining wall
appears as the most common problem-related geotechnical structure. During the last 10 years,
two accidents involving soil excavation and retaining walls have occurred on construction
sites in Lithuania.
The second part of the interview was dedicated to the geotechnical risk of the stages in the
installation of flexible retaining walls. The enquiry was aimed at determining the risks
involved and the consequences incurred.
Assessment of the construction practice of flexible retaining walls led to the identification of
seven stages of construction (Tables 5–9):
 Stage 1 – driving an H-beam into the designed position;
 Stage 2 – first-level excavation;
 Stage 3 – installing an anchor;
 Stage 4 – excavation up to the designed position;
 Stage 5 – installing piles next to the wall;
 Stage 6 – installing the first overlay;
 Stage 7 – installing the second overlay.

10097
Geotechnical Risk Identification: Case Study of Flexible Retaining Walls Installation

3.2.1. Interviews for the geotechnical risk of the steps in the installation of the flexible
retaining wall
The respondents were asked to assess the compliance of the calculation scheme with the
technological one and to identify the relevance of the aforementioned risks, consequences,
and likely conditions to be observed at each stage and to recommend preventive measures to
be undertaken to mitigate the risks.
Analysis of the calculation schemes showed that only two respondents underlined that
pressure tubes sometimes formed intermediate cast-in-place that should affect the
calculations of flexible retaining walls. Therefore, it was necessary to assess whether the load
from the pipe could affect the retaining wall at all stages. As for the other stages, half of the
respondents pointed out the following:
 in Stages 2 and 4, the calculated depth of the excavation has to be taken into account when
estimating the possible inaccuracies of the excavation rather than accepting a standard
size;
 in Stage 5, cast-in-place formation opposite the wall destroys the foundation of the
retaining wall and therefore it is necessary to estimate this in the calculation scheme
(Figure 9).

Figure 9 - Comments on the compliance of calculation schemes with technological

schemes.

The tables below (Tables 5–9) show the summarized answers to the questions about risks
arising and their consequences and conditions for the emergence of hazards occurring in each
stage. The numbers in brackets next to the risks and conditions for risks indicate the number
of respondents who named them.
The smallest number of risks were identified in Stages 6 and 7 (Table 5).
The most frequent ones involve the following:
 too-deep excavation (Stages 2 and 4, Tables 8 and 9);
 deviations from designed anchors and beam anchors or insufficient bearing capacity
(Stage 3, Table 6);
 foundation weakening caused by anchor installation (Stage 5, Table 7);
 H-beam deepening and related risks (Stages 1 to 3, Tables 6 and 8).

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 Danute SLIZYTE, Natalija LEPKOVA, Rimantas MACKEVICIUS

Table 5 - The analysis of risks, consequences, and conditions in the case study. Stages 6
and 7.
Stage 6 – Installing the 1st overlay
Scheme / risk of the Calculation scheme / Description / conditions
technological process consequence
Concrete is poured on the grate,
wall and overlay above formed
cast-in-place
In 28 days after laying concrete,
Question

temporary anchors are released

Loosening anchors will Collapse or deformations of Poor contact between the

move the wall (3) the retaining wall  crack overlay and retaining wall (2)*
Responses

in the pipe Calculation scheme does not

correspond to the actual
situation of the overlay (1)
Overlay design did not consider
horizontal loads (2)
Stage 7 – Installing the 2nd overlay
Overlays are produced
following concrete hardening
(in 28 days after laying
concrete)
One-story wall is concreted
Question

The overlay will not accept Collapse or deformations of Poor contact between the
Responses

horizontal loads (3) the retaining wall  crack overlay (2) and retaining wall
in the pipe Overlay design did not consider
horizontal loads (1)

*The brackets next to risks and conditions for risks indicate the number of the respondents who named
them.

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Geotechnical Risk Identification: Case Study of Flexible Retaining Walls Installation

The most common opinion about potential risk was obtained by analysing Stage 4;
foundation weakening within the process of forming cast-in-place pile was identified as a
risk (Table 9).

Table 6 - The analysis of risks, consequences, and conditions in the case study. Stage 3.
Stage 3 – Installing an anchor
Scheme / risk of the technological Calculation scheme / Description / conditions
process consequence
Beam anchors connecting two
neighboring H-beams are
installed.
A A
A Anchors the roots of which
make ~ 20 cm in diameter are
installed
In 28 days, the anchors are
pressed in up to the force
provided in the project

Section A-A
Anchor
Question

Anchor beam connecting H

beam profile

View A

Insufficient bearing Collapse or deformations of Clogged soil (1)

capacity of the anchor (3) the retaining wall  crack Inappropriate anchor installing
in the pipe technology (2)
Error in the project (1)
Responses

Spoiled material (1)

Anchors are fitted at a larger
angle to protect pipes (1)
Pipes damaged during Crack in the pipe Clogged soil (1)
anchor installation (1) Inaccurate information about
the location of the pipe (1)
Deviations from the project (2)

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 Danute SLIZYTE, Natalija LEPKOVA, Rimantas MACKEVICIUS

Inappropriate anchor installing

technology (1)
Big deformations or Collapse or deformations of Deviations from installing H-
collapse of the beam anchor the retaining wall  crack beams: distance are too large
(5) in the pipe (2)
Too small profile of beam
anchors has been selected (3)
H-beams are interconnected
only in pairs not using a
continuous beam anchor
(5)
Excessive deformations or Collapse or deformations of Looser soil than that found
collapse of H-beams (2) the retaining wall  crack during investigation (2)
in the pipe H-beams are interconnected
only in pairs not using a
continuous beam anchor (5)

Table 7 - The analysis of risks, consequences, and conditions in the case study. Stage 5.
Stage 5 – Installing piles next to the wall
Scheme / risk of the technological Calculation scheme / Description / conditions
process consequence
Calculations of the retention Formed cast-in-place bearing
walls of stage 4 are used vertical loads of the retention
wall are erected
B B
Question

Bored pile

Section B-B

Bored pile

The foundations opposite Collapse or deformations of Cast-in-place formation is very

the retention wall are the retaining wall  crack close to the H-beam (2)
Responses

weakened (7) in the pipe Inappropriate cast-in-place

formation technology, cast-in-
place forming weakens the
foundations (6)

10101
Geotechnical Risk Identification: Case Study of Flexible Retaining Walls Installation

Loss of overall stability  Cast-in-place formation is very

crack in the pipe close to the H-beam (2)
Inappropriate cast-in-place
formation technology, cast-in-
place formation weakens the
foundations (6)

Table 8 - The analysis of risks, consequences, and conditions in the case study. Stages 1
and 2.
Stage 1 - H-beam deepening into the designed position
Scheme / risk of the Calculation scheme / consequence Description / conditions
technological process
The site is enclosed
Construction site inserting H-beams into
enclosed by the fence
the designed situation
City street
Question

High pressure
sewage networks
D=400 mm
H-beam profile
between
them1,00 m

Designed deepening is not Collapse of the retaining wall or Clogged soil (1),
achieved (2)* deformations  crack in the pipe inappropriate types of soil
(strong clay, rubble) (1)
H-beam inserted into the crack in the pipe
pipe (1)
Deviations of H-beams Project correction  increase in
Responses

from the plan (2) costs

Solidified soil under the Deformations of the foundation Vibration (6)
pipes (2) under the pipes  crack in the
pipe
Solidified soil under the Deformations of the foundation
road (1) under the road  deformations of
the road
Collapse of pipe Crack in the pipe
connections (1)

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 Danute SLIZYTE, Natalija LEPKOVA, Rimantas MACKEVICIUS

Stage 2 – 1st level excavation

Level 1 is excavated to be
fitted with anchors
To prevent sand
crumbling, planks are

Hd
H

embedded between H-
beams
Question

Beam fixing the plank

Hd=1.1H
Plank
but not exceeding
Hd=H+0.5

Cavities form between Soil moves behind the retaining Crumbly, dry soil,
planks and soil matter form wall deformations of pipe recommendations are
(2) foundations  crack in the pipe neglected when work is
done’ (3)
Larger load than that Collapse or deformations of the The project does not
expected in the road zone retaining wall  crack in the pipe provide the possibility of
(1) carrying heavy loads,
transport weight is not
limited (1)
Separate H-beams can enter Collapse or deformations of the H-beams are not
the layer of the unexpected retaining wall  crack in the pipe interconnected,
Responses

looser soil insufficient soil

(3) investigation (4)
Planks break (2) Soil moves behind the retaining Distances between H-
wall  deformations of pipe beams are larger than
foundations  crack in the pipe those provided in the
project (2)
Heavier load acting on the
planks than that provided
in the project (3)
The excavation is deeper Collapse or deformations of the Improper control during
than that provided in the retaining wall  crack in the pipe construction (1)
calculation scheme (4) Misunderstandings
between the construction
parties (5)

10103
Geotechnical Risk Identification: Case Study of Flexible Retaining Walls Installation

Table 9 - The analysis of risks, consequences, and conditions in the case study. Stage 4.
Stage 4 – Excavation up to the designed position
Scheme / risk of the Calculation scheme / Description / conditions
technological process consequence
Excavated up to the altitude
of the designed foundation
pit

Hd
H

Hd=1.1H
but not exceeding
Hd=H+0.5m
Excavation is deeper than that Collapse or deformations of the Improper control during
provided in the computation retaining wall  crack in the construction (5)
scheme (5) pipe Misunderstandings between
the parties of construction
(2)
Loss of overall stability (2) Collapse or deformations of the Too short anchors (1)
retaining wall  crack in the Anchors are installed at a
pipe sharper angle of inclination
than that provided in
calculations (1)
Overall stability is not
verified (1)

On requesting recommendations regarding preventive measures that could be taken to reduce

risks, experts’ comments regarding all the design and construction stages of the retention
wall involved remarks indicating that having a detailed project and sufficient time to prepare
it, the collection of sufficient data on the environment and geological conditions, permanent
structural monitoring, and close cooperation between all construction participants are the
aspects that have a powerful effect on work quality and the reduction of errors. Reducing or
eliminating pressure to decrease stress in the pipes was mentioned as a specific requirement
for this structure during construction.
Additional preventive measures distinguished by stages are as follows:
Stage 1 includes the application of other technology for the installation of the retention wall,
maintaining a safe distance to the pipes, conducting geotechnical studies of sufficient scope,
and collecting a substantial amount of relevant data on the location and condition of the pipes.

10104
 Danute SLIZYTE, Natalija LEPKOVA, Rimantas MACKEVICIUS

Stage 2 covers control of the depth of the excavation and the careful installation of planks to
minimize soil crumbling.
Stage 3 involves the process of making a continuous beam anchor that integrates H-beams
and anchors into the common system; all anchors must be tightened and tested in accordance
with the requirements for normative documents, the depth of the pipelines must be adjusted,
a sufficient distance from the borehole for the anchor to the bottom of the pipeline must be
maintained, the drilling angle must be monitored, and the designed injection area must be as
far as possible beyond the pipelines.
Stage 4 keeps control of the excavation.
Stage 5 embraces the selection of cast-in-place formation technology that should minimally
damage the foundations of H-beams and form cast-in-place as far from the H-beams as
possible. The stage also points to forming cast-in-place with pauses to reduce temporarily
weakened areas.
The interview was informal and had no time limit. Although the face-to-face interview
approach was used and assisted in clarifying the situation, there was no respondent who
should focus on all the risks listed in the table.
One of the respondent designers (Structural Project Manager) described situations and
calculation schemes as logical and thoughtful and therefore did not face any risks in the
process of installing flexible retaining walls. The surveyed architect, project manager (PM)
distinguished only deviations from the design situation as risks that could affect architectural
decisions.
The respondents agreed with the opinion that the greatest loss in the given situation would
be caused by a breakdown in the pressure pipe and pollution of the natural environment by
wastewater. Also, breakdown in the pressure pipe was mainly mentioned when assessing the
final consequences of the risk.

3.2.2. Drawing the Cause and Effect Diagram

One of the major outcomes identified in the interviews was breakdown in the pressure pipe,
which would lead to the greatest loss. After scrutiny of the data obtained from the interviews,
to further clarify the possible causes of breakdown of the pressure pipe, a brainstorming
session was held. Five experts who cited the majority of risks during interviews (one
geotechnical expert, one designer (Structural Project Manager), two geotechnical designers,
and one construction manager) were selected as participants. First, the participants were
briefed about the case of breakdown of the pipes, and six categories of causes, namely
technology, time, management, environment, people, and structures (geotechnology), were
identified. Then they were asked to come up with as many causes of such an incident as
possible. Finally, all the possible causes cited for the breakdown of the pressure pipe (the
effect) were used to construct the cause and effect diagram (see Figure 10). The findings are
summarized below:
Structural-geotechnical causes
 structural members of retention walls (H-beams, soil-retention planks, anchors);
 technological processes related to the installation and testing of structural members
(vibration, cast-in-place formation opposite the retention wall technology);

10105
Geotechnical Risk Identification: Case Study of Flexible Retaining Walls Installation

 pit excavation (information included in the project, match with the calculation
scheme, control over altitudes);
 initial information and the project (geological and engineering investigations, the
place of the pipes in space, project finalization and application of technology used,
the accuracy of calculation schemes, the amount and accuracy of all information).
Environmental causes
 accuracy and content of geological and engineering investigations;
 information on the surrounding buildings and structures;
 loads and impacts (e.g. transport, seismic, technological).
Technological causes
 technologies used in the construction of structures and their negative effects on the
structures or their members.
Managerial causes
 poor organization;
 frequent changes in projects;
 excessive workloads;
 insufficient experience of installing BIM systems.
Time-related causes
 busy work schedules that disregard technologies.
Staff-related reasons:
 poor communication between stakeholders;
 lack of staff;
 errors in taking control of the project;
 errors in developing the geotechnical project.
Brainstorming disclosed that answers to the question of ‘why it might happen’ were based
on:
 experience gained in the individual’s and company's projects or acquired by analysing
past failures in other projects;
 theoretical knowledge obtained during studies or on training courses;
 directions provided by regulatory documentation describing investigation, design, and
installation.
Although the aim of the participants was to identify the risks of installing retaining walls and
determining their causes while placing major focus on the retention wall as a geotechnical
structure, other causes of risks related to technology, time, management, environment, and
human resources were identified too. The selected team has to ensure the representation of
all stakeholders and participants of construction- the composition of the team needs to be
adjusted according to the intended goals. In this way, the project can be analysed in more
detail.
Based on these observations, one can conclude that the proper selection of brainstorming
participants can lead to good results when analysing geotechnical structures with respect to
risks.

10106
 e
Pu ven
rs o p
F
ui po
ng s
an ull
sy
Deviations from the Inaccurate information on
di ing
A ste aly ap ffe g
o
project
ut m to
p sis pro the position of the pipes
ho in th ren als a os
of val
rit th t, compa
b ers ar e D es si
th wi iff am som Th nch ma H-bea cted soil
Th y an on ian co
e p th er e To mu e or ll m vib un
ro no
ou in m mp en si eti ration der the pi
m
F
o ltan dis and
s t pe
gh flu
t e
an an po c u t a tua e C
result
sa rit
La ag y te ma eou ance the s in th s
ck se n
x em ls ica
D nde sses tion s fr au un or i In chn ll d sly e
m l
tia if rs s be pip
of pr l en Im
co om ses d e n st co ol i
ad

pipe is
es t r t all
e C ns th dis
po fere tan men

ectl
co rre og stan wea twe e sh
he in e o

so
m se st nt din t
d sin
p o ct y ce ke

Incorr logy
g fo aus truc e ot sati pi g a
ly
S
pe Te ruc p
s b ne n th e is
te ch tur ex os g ri f
iti sk llo es tio he sfa pe nc se et d a e

y sele
wi di n r p ct th oil
nc ce D roje le
s a ho E
we r
e on
i o pr
no e a
C ss ng str act art ion
ev ct cte
re rs
to lo re o en eas
so ia d
re pr ust ors ies o nco nv se op

cted
f

Loose not compa

gi n
Ca tec alcu ca ot qu
op in of
In f the tion w , th de bsta un esti defi erti

ct
e
d lc hn
os th S eak e
ac p
technology is selected
lat l i co ire
m pr epe cle tere gat ned es d
i

techno il under th ed
io
al e
ul o m n fr

side of passive pressure

s
cu ro s fro
Po esig ati lo n en ra In om ra je m pl oil c en fou oj n s d
ec in pr u on. du o n
pa sid
an ru ed nd
V
sd
k m
Invalid anchor installation

a
on gic ts
o rin ot
or n p ct er th
a t g a ev nd
So ted su th te d ct
g m
e si b
anchor length is not reached
tio
co ro s o ed
Insufficient competence of the
il pr ibra
sc l p ffi e
n

The excavated pit is too deep

m m nt le
Weakened foundations on the
o p fo ent ergr
Due to obstacles, the required
ns op ti so ee
he ro not cie arc esig
o sp e
m th
llo fro ou il t
m ot
staff in charge
m ce
a e nt hiv n
sp la rly ng p
un er es s In f em rope
tc wi m nd
o
h su p in e ac ci
D se w ng
ic an l f
naccurate description of The anchor is pulled up
do ses f rti
a o o es ng
L t
sc es
do tio d m no h H fici ye
- a rm le er he
Works are behind schedule controllable indicators in the
c n a b e n s e re str os cte i in
The anchor is too loose
V u tc em
d sn
Th e ati
ar m wi int o e en s o
technological project A
no on H suf
s gt f ot
e d am t ex
h H
ia en th en rre t
In Excessive workload
tio ts th an sp ist s is pe Ex pl -be fici
to nch or -b
e
ns on an to rie ce ace am en
ge cor
e t ce
Inappropriate measurement methods in or
d ce o n sta am
te i
in ec
ot re
ss o s a t d

Ex
iv f
bi
control
control

ec ct g
and devices are selected
hn be lar ce
In

ce
no
Lo rme nsta la lit
e d fix re i epth
hn ly y
ic tw ge Th
S
rm a

ssi
ss di lla
Ex eote
is too weak
in cor ic sel l ee ef in nst
Poor communication with geotechnical ea
Ex yer
ve re n

ve
ce ch
of ate tio
Poor quality
Poor quality

ati
al ec
o r g t al
sti ct ca te
ve In ss ni d ce of de oil p nc m he led
and technological design promoters ov su n c

de
ga ly te d
su i v ca s s fo fin ro ho
ati a
E er pp au Th

fo
ed pe ri

r
go
Ex eep iv un
e
eu lc on nc at a
tio sel A al r
ffi
g rro
el d
n ec ry
ci nc on ca
l s orts ses du tie an st at hor n

fo mat
oo
The prestressed load

oa ati
m te p lim eo rs ta
en
da
va th
A rin s d ch
er dit
m w
ds on e
bi g o o
ta io
eth d
tc tio
provided in the project

un ion
ob arti ite tech in d r

ns
in n nc n lit ag ea
on s
y

da o
om
od so no

Errors are committed

capacity
Loss of working
e is k
ty s

tio f
ta cul d i
s
ho th
Li in ar kn nica esig il t m b Calculations of the anchor do not
pe rs st
in
of o
ro
te In o
et

Poor communication between stakeholders

de ttle ed fie ow l p nin Th k
ar
r ve ee

The level of
su

Increased dissatisfaction
correspond to the scheme

with work
responsibility decreases
op
du ld le
nc
sig e en

is too small

Errors in taking control over

Lack of human resources

the project
co e c
et
In sti t th
ffi
rin h dg ojec g a
eo oo
ni xpe cie rre al ga os
'st suf ng ri g as e o t Deviations increased distances
fd
r f e s b sp cu tio e
nt sh
n
es
on lat
or
t
between H-beams
ig de
Th ang icie suc nce tudi een f th
h o es is d ion
ep
to
ne
co e u e' a nt rs of
T
ns se cc inf stru f People w H th sch
of passive pressure
id o id or d e a em
er f e m ctur
-b
at rain es
Co eak ea ct e

The selected cross-section

te in ca cal nts ati
Ruined soil on the side
A ama m ua do
nt g lc cu on C
nc g rro en
s l s es
of passive pressure

io is
n ul la ab
ho e t sio ed
t tru n
the beam.

at tio n h op ast-
pa
da ri ot
io n ou ct ot po in
id n
The excavated pit is too deep

t
ns he pr e p
Designers are not competent ur
Th ma
sc e sit -pl
oc ip
as pro
tal p
e e Th
member is selected

Structural e v ge
s l a ip
an su gr enough
ss e H ac
t
ib to
m am
tio e
dir e pi
D -b e fo
es

Anomalies
ra t n
pt s
io d
tin he ha
ire ec pe ea un
Poor communication with the Th tly is A
ha

technological project
Errors in developing a
ns oe
g pi ve
ct n m da
d
o sc
hit s a ti
geotechnical design promoter ef vib e pi
H pe
sn -b au
ee ex
Weakened foundations on the side

ot fe ra t p e i p c fte on
Ch f co ea se
and technical maintenance ct r d is
m d ion s a (e ava
o f

material about the structure

Lack of the archival
x
an ord
n an ec f ig fo
The wrong anchor as a structural

ca ted
ge in ca
s i ate u us th d c te v gi rm
in n s es ep rac d b at pit ng ed

Sp e
th U nde
ip ks y io is ap
e ns t
Inappropriately selected profile of

In the
it
es nd re
defined during soil investigation

ac p
Soil properties do not meet those

ys er sti
ManagementI I a oo

cific
Busy work schedules are
cu la gr m
ra n te
m ou ate nd

ground test
Small-amount
accepted as a priority
te
II)

c on
lo nd d
project

In

brainstorming.
Lack of knowledge e
ca pa
ac

ditio
tio rts
cu n
In ra
ar
e
ac te

are ns on
cu
ra lo L
the soil

te ca va oad

not the
ess
tio
lo n lu s e

ed
ca in es x

ass site
tio th fo cee
n
Poor quality control

ep r t di
in lan
hi ng
sp t Are
th Are
structural materials

es ar he unk
tic no not now
ec In n
Installing the BIM system
lacks use experience
ul rm c on
tio te cor sid

Inappropriate allocation of
the schemes for the technological

n ar a
Calculations do not correspond to

workload and responsibilities

ch re ere

structures
no ct ob tiv d

Frequent changes in the project

jec e

Poor information flows between

lo as

construction participants
risk as
gi se t y
short
Technological breaks are too
Fails to assess variations in the
Fails to assess the properties of

ca s s

Changes in the system of

Inaccurate archival

heights
schemes
Rush leads to inaccurate
technological processes

ll m Time
oa en
properties of structural materials in

ds t o
f
The project does not provide a possible
calculation-based altitude of excavation

Surrounding buildings and

Technological

Loads and impacts

Environment

conditions
Geological
Properties of the soil Soil layers
retaining wall.

Vibrations have a
negative effect on Possible deviations
foundations. from the project.

Anomalies
Installation technology for the
Anchor installation technology

Vibrations have a negative

Small-amount ground test

Local weakening of
Technology for installing internal foundations

effect on the pipe.

Figure 10 - The cause and effect diagram according to the information collected during
foundations.
weakens the base on the side of passive pressure

Unrepresentative investigation
samples are taken
been broken
A high-pressure
waste pipe has

Misinterpretation of results
Inappropriate testing
The sample is damaged at the
preparation stage.
Danute SLIZYTE, Natalija LEPKOVA, Rimantas MACKEVICIUS

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Geotechnical Risk Identification: Case Study of Flexible Retaining Walls Installation

4. DISCUSSION
Based on the analysis carried out, the authors of the paper proposed risk identification of
flexible retaining walls using a risk management flow based on Mishra et al. [8] and ISO/IEC
31010:2009 [24]. In the future, this chart (Figure 11) can be verified by analysing other
geotechnical structures. For the effective application of risk identification in flexible
retaining wall risk management flow, a well-prepared team representing all interested parties
should be created.
Data collected on the investigated structure. A detailed project, including calculation
schemes, descriptions of technology, and the work order, is developed, and all information
on adjacent buildings and structures and data of geological engineering exploration are
obtained.
The collected information assists in establishing the content, thus allowing the risk
management objectives, criteria, and assessment programme to be identified and coordinated.
If the required information is missing, data are added before proceeding to the next stage.
The purpose of risk assessment is to help make decisions based on the results of risk analysis,
define the risks to be reduced, and set risk reduction priorities. Risk assessment includes one
or a few options for changing risk and implementing these options.
First, the risks are identified, which involves all pre-selected construction participants and
interested persons, for example, by applying the face-to-face interview approach.
Brainstorming is used to identify risks. To facilitate risk management, the installation of the
flexible retaining wall should be divided into technological stages.

The selection of the interested parties of

construction for risk identification

Collect the data

Establishing the context

Communication and consultation

Monitor in real - time and review

Risk identification
Risk assessment

Risk analysis

Risk reduction

YES
Risk acceptable

NO
Treat the risk and analyse reliability

Figure 11 - Risk identification in flexible retaining wall risk management flow according to
ISO/IEC 31010:2009 [24] and Mishra et al. [8]

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 Danute SLIZYTE, Natalija LEPKOVA, Rimantas MACKEVICIUS

At the stage of risk analysis, the probability of occurrence of the appropriate type of risk is
estimated. The consequences established at the risk identification stage are also assessed; that
is, their impact on the project and its related activities is evaluated.
The stage of selecting preventive measures, reducing risk, and analysing the reduced risk
completes the risk assessment. Thus, the question of ‘whether the risk is acceptable’ arises.
The authors of the article propose that if the risk is not acceptable, the data collection stage
should be performed again to acquire new data. It may involve material for additional
geological engineering exploration or any other bonus information that may affect the risk of
installing the retaining wall. Then, everything is repeated again. At the risk assessment stage,
the processes of risk identification, analysis, and reduction are very closely interrelated and
therefore have to complement one other.
The participants must be involved in information exchange, tutorials, risk monitoring, and
review within the whole process. In order to identify risk, first of all, the selection of all
construction participants involved has to be made. They may analyse geotechnical risks and
related problems. The proposal is based on the analysis carried out in this article and on the
observation that not all construction participants having experience in the field of
construction - are able to identify geotechnical risk (see Section 3).

5. CONCLUSIONS
Analysis of the scientific literature with reference to the topic of the article shows that the
risk of collapse or deformations of flexible retaining walls has not been widely analysed.
In order to determine the risk of installing flexible retaining walls, the authors of the article
used the face-to-face interview approach, brainstorming, and a cause and effect diagram. A
specific case study is presented.
The examination of the specific case (interviewing) demonstrated that the respondents
identified risks and proposed additional preventive measures. The respondents expressed the
same opinion about the given situation and agreed that the greatest loss would be caused by
breakdown of the pressure pipe and pollution of the natural environment with wastewater.
Also, breakdown in the pressure pipe was the most frequently mentioned option when
assessing the final consequences of risks.
Investigation of the data obtained during the face-to-face interview was based on
brainstorming and the cause and effect diagram: five professionals who had monitored most
of the risks were selected with the help of the face-to-face interview. The thoughts expressed
during brainstorming were used as the basis for drawing the cause and effect diagram.
The study found that the face-to-face interview approach could only be applied to risk
identification in simple cases and was suitable for preliminary screening of the respondents
involved in brainstorming. Thus, the face-to-face interview approach should provide an
identical or similar situation in order to independently assess the competence of would-be
respondents considering a particular issue.

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Geotechnical Risk Identification: Case Study of Flexible Retaining Walls Installation

Geotechnical experts are more trusted than other construction participants when expressing
their positions on objects not related to it or the company that employs them. Cooperation is
also smoother if reasoned statements are made.

Acknowledgements
We express our sincere gratitude to our colleagues who have been willing to discuss the ideas
and who made comments at the early stage of development of this paper.

Conflicts of Interest
The authors declare no conflict of interest.

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