4. Geotechnical risk management.

4.1 General

Ground conditions can never be totally certain and invariably constitute a significant risk for all projects. Some ground uncertainty will always remain in most projects even after the most rigorous design procedures.

In recognition of this ROADEX Partner countries tend to follow some form of geotechnical risk management process for their road construction and improvement works, and particularly for those involving peat, so that any geotechnical risks are identified ahead of the problems on site, and efforts made to correctly manage them. Eurocode 7 recommends a geotechnical design and risk management process for road construction and improvement projects as below:

The role of geotechnical risk management and the Geotechnical Risk Register (GRR) through a project can be seen in the following chart.

Preliminary Geotechnical Investigation

Ground Investigation (Preliminary Geotechnical Report)

↓ ↑

Sufficient information?

Geotechnical Design (Geotechnical Report)

Construct Works

Geotechnical Feedback Report

Recommended geotechnical design and risk management process for road construction and improvement projects from Eurocode 7.



Geotechnical design and risk management processes can be applied to all projects, large or small, as part of a continuous management process over the life of the project, the only difference being the level of work considered necessary to meet the needs of the project.





Reports and engineering positions can be updated and amended as new information becomes available and the geotechnical risk is assessed.

Project Stage Action Geotechnical Risk Management
Planning Preliminary assessment Commence GRM & GRR
Design Detailed design Update GRR
Construction Construction of Works Update GRR
Operations Maintenance Update GRR

4.2. The preliminary geotechnical investigation and report

The Preliminary Geotechnical Investigation is the first stage in the process. It considers the geotechnical risks of the various options for the project and offers guidance on them. A typical preliminary geotechnical investigation report will include details of:

  • the desk studies carried out, e.g. geological maps and records, aerial photographs, mines and mineral workings, previous ground investigations, flood records, contaminated land, etc.
  • the site visits made, e.g. the initial walkover, geomorphological & geological mapping, probing, trial pits, samples and testing, drainage/hydrology, etc.
  • the ground conditions – soils on the site and their engineering properties, significance of geological formations, ground water conditions, etc.
  • a comparison of the options and risks
  • recommendations on instrumentation for site monitoring and the frequency of readings.
  • the Geotechnical Risk Register

4.3. The geotechnical report

The Geotechnical Report is the main geotechnical interpretation report for larger projects and includes details of all of the investigations carried out together with the design of the geotechnical structures. The report builds on the initial report and updates the Geotechnical Risk Register with any new risks identified together with any mitigation measures.

4.4. The geotechnical feedback report

The geotechnical feedback report is the formal record of all of the geotechnical matters encountered during the Works. This report is started at the beginning of the construction works on site and typically comprises a full record of the ground conditions, materials and structures used, testing carried out, instrumentation, monitoring, design changes any problems experienced during the Works. This report should be safely recorded in a central library as a collective learning document for future projects.

4.5. The geotechnical risk register

The Geotechnical Risk Register is the key in the geotechnical risk management process. It systematically records and considers all of the risk identified in a structured fashion and ensures that they are dealt with. Each hazard is considered as 4 steps:

  • The identification of the hazard
  • Assessing the probability of it occurring and its impact if it did
  • Managing the risk identified
  • Allocating responsibility and action
    Risk = Probability x Impact

Good communication between client, designer and contractor is essential for this process to work. When all parties are working together openly on the project there is a better chance of any risks being identified and considered early enough to offer solutions, or put contingency plans in place.

Examples of pages from a risk register for a new thin embankment over peat are shown in the following tables:

Ideally, only trivial risks (1-4) should be accepted, but in practice this will not always be possible. Risks with a value above 9 should not be accepted. These should be reduced to less than 9 by appropriate risk control measures, i.e. management and/or mitigation. An example of this is shown in Table B below.
An alternative method of presenting risk rating as a matrix is shown below in Table C
In the above examples the geotechnical risk has been measured in terms of the potential delay to the delivery of the Works. An alternative method for environmentally sensitive sites could be to measure the “Impact” as the impact of the geotechnical hazard on the environment.