TECHNICAL | TUNNELLING IMPACTS
Monitoring, Control, and Validation of Design
Assumptions a. A well-thought-out and carefully planned monitoring system will provide useful information for validation of the design assumptions relied upon by the assessors and provide ongoing assurance to the utility. The monitoring results will also be used to confirm adequacy of the measures controlling the works.
b. The Instrumentation and Monitoring (I&M) plan should include the type and location of monitoring points, frequency of data collection, data interpretation method, trigger levels and action plan.
c. The action plan should include a strategy to cover what to do in an event of a breached trigger level (e.g. termination and/or modification of the construction/mitigation processes; change in monitoring and data review frequency).
d. Continuation of post-work monitoring until cessation of significant ground movements has become normal practice. For some recent major infrastructure projects, the monitoring works have been terminated when the settlement rate is less than 2mm/year.
8 CONCLUSIONS This paper provides a guide to the assessment of pipelines subject to impact from various construction activities. In summary, a pipeline risk assessment comprises six key components including ‘Conditions’, ‘Calculations’, ‘Consequences’, ‘Control’, ‘Consent’ and ‘Conciliation’, and these form the components of the three-stage assessment processes. The presented methods and strategies are drawn from the authors’ experience of the assessment processes developed through their works in London and the Thames Valley over the last two decades. This paper is intended to be as general and
informative as possible so that the assessors will be equipped with appropriate tools to go through the impact assessment processes and have a positive dialogue with the utility. The ultimate goal is to achieve a ‘reasonable and optimised’ solution which is acceptable to both parties, is truly ALARP and most importantly, takes a holistic view of risk.
9 ACKNOWLEDGEMENTS Any views expressed in this paper are those of the authors and not necessarily those of Thames Water Utilities Limited or any other utility.
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