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spective owner-sControl and Monitoring of Tunnels and Underground Space

27-29 November 2017 - Thimpu, Bhutan

Tunnel Monitoring – Contractual Roles and Responsibilities

Alexandre R.A. GomesITA Vice-President

Chief Technical Principal Tunnels and Underground, SMEC


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Control and Monitoring of Tunnels and Underground Space27-29 November– Thimpu, Bhutan

1. Contractual Framework• Recommendations / Contractual Forms

2. Geotechnical Safety Management Plan • Observational Method / Geotechnical Safety Management Plan / Risk

Management Plan / Important Aspects / Requirements

3. Typical Roles and Responsibilities• Typical Organisation Entities / Typical Organisation Structure / General

Roles and tasks in the OM / Tunnel Designer, Consultant / Site Supervision, Geotechnical Engineer /

4. Procedure• Typical Procedure / Example of a project / Geotechnical Meetings /

Warning and action levels / Design of Corrective Measures

Summary

Contractual Roles and Responsibilities

By Alexandre R.A. Gomes


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Recommendations for the Implementation of Tunnel Monitoring :

• The contractual framework must be conducive to the operation of the observational method.

• The client must be aware of the benefits of the tunnel monitoring and consider an adequate integration into the overall project construction and risk management process.

• Fair contractual practices and risk allocation, cooperation between the parties and incentives for performance excellence.

Tunnel Monitoring - Contractual Framework



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Contractual Forms and Tunnel Monitoring:

• The form of contract has considerable impact on the method of delivery and consequent wording of the contract clauses changes as responsibilities vary between different types of contract.



(Dix and Smith, 2006)


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Many Alternatives


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Contractual Forms and Tunnel Monitoring: Some FIDIC suit of contracts for procurement:



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• More flexibility with regard to different task allocations between owner and employer.

• Based on a Design-build contract, but can be modified to a design-bid contract.

• Contractual risk allocation in accordance with basic risk management principles. Ground risks lie with the employer as the party who can best control these risks.

• Use of a Geotechnical Baseline Report” ("GBR") to establish expected sub-surface conditions.

• Adjustments of time for completion and contract price for changing conditions.


Contractual Forms and Tunnel Monitoring: New Emerald Book for Tunnels- FIDIC-ITA Working Group

Project Timeline


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ITA has recommended application of certain principles and practices into tunneling contracts:

• WG-3 Contractual Practices

• “ITA Recommendations and Contractual Sharing of Risks”

• “ITA Position Paper on Types of Contract”

• “The ITA Contractual Framework Checklist for Subsurface Construction Contracts”

• “Guidelines on Contractual Aspects of Conventional Tunnelling”


These recommendations of best practices are positively permeating the industry.


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Tunnel Monitoring – Geotechnical Safety Management Plan

Nicholson, 2012

“The Observational Method in ground engineering is a continuous, managed, integrated, process of design, construction control, monitoring and review that enables previously defined modifications to be incorporated during or after construction as appropriate. All these aspects have to be demonstrably robust. The objective is to achieve greater overall economy without compromising safety.” CIRIA 185 (1999).


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Tunnel Monitoring – Geotechnical Safety Management Plan “The processes of planning,

design, construction and maintenance of tunnels are (or should be) closely inter-related. In certain countries, current practices tend towards artificial barriers and discontinuitiesbetween certain of these aspects, particularly that of time separation between design and construction; it is not surprising there to find a high frequency of avoidable hazards and frustrated contracts.” Muir Wood (1975)


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• Prior to construction a geotechnical safety management plan (GSMP) has to be established.

• Contents and extent of the GSMP have to be adjusted to the specific requirements of a project.

• Targets are safe and economical. construction, while effectively controlling the residual risks.

• It is an inherent part of the overall Risk Management Plan.

Tunnel Monitoring – Geotechnical Safety Management Plan Geotechnical Safety Management Plan (GSMP):


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Tunnel Monitoring – Geotechnical Safety Management Plan Risk Management Plan (RMP):

Goricki, 2013


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Tunnel Monitoring: Geotechnical Safety Management Plan

Aspects to be defined in the GSMP based on Tunnel Monitoring:

• Contact details

• Roles and Responsibilities

• Geotechnical meetings

• Observation program

• Definition of expected behaviour

• Action levels

• Warning levels

• Organisation and communication

• Leadership

• Priorities


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Key issues to be addressed by the Tunnel Monitoring Plan:

• Design concept for assignment of excavation and support.

• Determination of safety relevant parameters, including definition of target behaviour and criteria for the assessment of the stability of the system on the basis of the expected ground conditions.

• Monitoring concept, allowing a continuous comparison of expected and observed behaviour including all organizational and technical stipulations.

• Management concept for cases where ground conditions and/or system behaviour deviate from the predicted, both for favourable and unfavourable deviations.


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Contact details

• Contact details and function of all responsible persons shall be listed.

• For safety relevant functions it is advisable to nominate a proxy.

• Besides the project team this applies also for third parties (stakeholders) like owners or managers of buildings, structures (e.g. rails, roads) and utilities (e.g. gas or water pipe) in the influence area of the site.

Information management

• The staff must be instructed that all geotechnical information shall be reported without delay.

Leadership

• The functions may be different in case of routine work and emergency

• For the case of emergency it shall be clear who is in charge to coordinate all above functions



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evaluation and analysis of the data should be preferably executed by the party carrying the geological risk.

• Experienced parties must be assigned for the installation, commissioning and operation of instruments as well as for face mapping / geotechnical documentation and interpretation of monitoring results.

• Clear communication flow and procedures and clarity over roles and responsibilities.


Requirements for Tunnel Monitoring Implementation:



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provisions should guarantee that data evaluation is made available to all parties involved in the project and is rapid enough to allow for successful implementation of mitigation measures.

• All steps of the process (measurement, evaluation, interpretation, recommendation of mitigation measures, decision, supervision of execution) shall be documented.

• Tunnel monitoring should be integrated as part of the geotechnical safety and Risk management plans


Requirements for Tunnel Monitoring Implementation:



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Control and Monitoring of Tunnels and Underground Space27-29 November– Thimpu, Bhutan ©Handbook Geotechnical Monitoring in Conventional Tunnelling, Austrian Society for Geomechanics

Typical Organisation Entities:

1. CM - Client / Construction Management

2. PO – Owner’s Project Representative

3. OT – Owner’s Technical Representative

4. CO – Contractor

5. ENG – Engineer

6. D – Designer / Consultant

7. GE – Geotechnical Engineer on site

8. MU – Monitoring Contractor / Geotechnical Monitoring

9. IE – Independent Expert / Controlling

10. CHE – Checking Engineer

Tunnel Monitoring: Typical Roles and Responsibilities


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• Typical Organisation Structure:



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Modified from Bles et al 2015

Role Task with respect to the Observational Method

Third parties: authorities, insurers

Approval of design

Client or main contractor

Verification of scenarios (both design and corresponding working plan, plus choice for switch moments). Also intangible risks are taken into account (eg. politics and reputation).

Decision maker / Owner’s Project Representative

Decides about switching between scenarios, informs the client and third parties and provides feedback to consultants and contractor.

Designer Makes design and scenarios, drafts the monitoring plan, tunes with monitoring coordinator, advises the Owner’s representative.

Owner’s Technical Representative

Enables an effective execution of the project, guards the monitoring limits and discusses the observed behavior with the designer. Adjusts the course of action after a switch moment and releases the project.

Monitoring coordinator

Leads the measuring team, reviews measurements and data processing, provides feedback to decision maker,

Monitoring contractor Executes the measurements and informs the monitoring coordinator

General Roles and tasks with respect to the Observational Method



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Tunnel Designer / Consultant:

• Development of the monitoring plan and its update.

• Site-specific priorities shall be defined for different possible emergency scenarios.

• Prior to construction the designer defines the target behaviour and effects of tunnel construction on the surface and structures based on empirical or analytical stability considerations (essential part of the detail design), defining acceptable levels and mitigation measures.




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Tunnel Designer / Consultant:

• Target behaviour and limits and criteria of acceptable behaviour are stipulated typically for the following parameters:• Displacements

• Lining utilization

• Face stability

• Water inflow

• Surface settlements

• Displacements and allowable distortions of deflections of buildings and utilities; e.g. building, rails, water pipes and sewers, gas pipes, etc.

• Target behaviour can be expressed in forms of scalar magnitudes, vector velocities, ratios, etc.

• The target behaviour shall be updated during construction, as required.




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Site Supervision / Geotechnical Engineer:




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• Organizational unit (geotechnical engineer, or team) in charge of analyse all observations in a broad context, including: • Geological aspects (face mapping, geotechnical model update

and interpretation, etc.)• Monitoring data and

• In-situ observations, etc.


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• engineer evaluates and interprets data and report to the site supervision, the contractor and the designer not later than the specified time.

• In case of unusual events the geotechnical engineer immediately reports to the stakeholders.

• These functions should Ideally be carry out by the designer.


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Abbreviations:

GE – Geotechnical Engineer on site

ENG – Engineer

CO – Contractor

IE – Independent Expert

D – Designer

CHE – Checking Engineer

CM – Construction Management

OT – Owner’s Technical Representative

PO – Owner’s Project Representative

Tunnel Monitoring – Procedure

Typical Procedure :


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Example from the Klang Valley MRT (KVMRT) Project, Malaysia

Vasagavijayan et al, 2015



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Geotechnical Meetings:

• Purpose of this meetings is the information of all stakeholders with respect to the observed behaviour as well as the predicted ground conditions and system behaviour for the following sections.

• In addition a comparison between predicted and actually observed conditions and applied excavation and support methods is presented and discussed.

• If required, design and prediction are updated.

• The GSMP shall contain stipulations regarding convening of meeting, intervals of meetings and participants.



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Geotechnical Meetings:

• For efficient communication it is advisable to make joint site visits of representatives of the contractor, the site supervision, geologist and geotechnical engineer.

• A short routine meeting after the site visit allows exchange of information.

• If required, changes in the excavation and support can be directly fixed at this meeting.



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Waring and Action levels

Generally the GSMP consists of the following action levels:

i. Observed behaviour complies with the target behaviour: continuous comparison to design values

ii. System behaviour on longer section more favourable than predicted: optimization of excavation and support

iii. System behaviour less favourable than expected: immediate implementation of mitigation measures as specified in the GSM, respectively initiation of crisis management

Traffic Lights System



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Tunnel Monitoring – Procedure and Responsibilities


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Warning Levels:

• The warning system shall be established to meet the project boundary conditions and requirements

• It consists of the following warning levels:



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• Example of warning, alarm criteria and mitigation measures



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• In case of deviation from the expected system behaviour one unit shall be responsible to design corrective measures, or choose such measures from a pre-designed catalogue

• Such unit may typically include:

• the geotechnical engineer

• the designer

• the client

• and/or engineer

• and especially in case of emergency, the contractor

• This unit shall provide a proposal to the decision unit

Design of corrective measures



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• Example of summary report in form of a table

Tunnel Monitoring – Procedure and Responsibilities


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Disclaimer

a) The speakers are presenting their own personal views and are not expressing the view of the Foundation.

b) Papers and documents displayed or handed out during the Event are copyrighted. The participants must observe and comply with all applicable law regulations concerning the copyright.

Control and Monitoring of Tunnels and Underground Space

27-29 November 2017 Thimpu, Bhutan

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