4 Supervision of construction, monitoring and maintenance
(1)P To ensure the safety and quality of a structure, the following shall be undertaken, as appropriate:
- the construction processes and workmanship shall be supervised;
- the performance of the structure shall be monitored during and after construction;
- the structure shall be adequately maintained.
(2)P Supervision of the construction process, including workmanship, and any monitoring of the performance of the structure during and after construction, shall be specified in the Geotechnical Design Report.
(3) Supervision of the construction process, including workmanship, should involve the following, as appropriate:
- checking the validity of the design assumptions;
- identifying the differences between the actual ground conditions and those assumed in the design;
- checking that the construction is carried out according to the design.
(4) Observations and measurements of the behaviour of the structure and its surroundings should be made, as appropriate:
- during construction, to identify any need for remedial measures or alterations to the construction sequence, for example;
- during and post construction, to evaluate the long-term performance.
(5)P Design decisions, which are influenced by the results of the supervision and monitoring shall be clearly identified.
(6) The amount of construction supervision and the quantity of field and laboratory testing required to control and monitor performance should be planned during the design stage.
(7)P In the case of unexpected events, the methods, extent and frequency of monitoring shall be reviewed.
(8)P The level and quality of supervision and monitoring shall be at least equal to those assumed in the design and shall be consistent with the values selected for the design parameters and partial factors.
(9) Annex J gives a checklist for construction supervision and performance monitoring.
4.2.1 Plan of supervision
(1)P The plan included in the Geotechnical Design Report shall state acceptable limits for the results to be obtained by the supervision.
(2) The plan should specify the type, quality and frequency of supervision, which should be commensurate with:
- the degree of uncertainty in the design assumptions;
- the complexity of the ground and loading conditions;
- the potential risk of failure during construction;
- the feasibility of implementing design modifications or corrective measures during construction.
4.2.2 Inspection and control
(1)P The construction work shall be inspected on a continuous basis and the results of the inspection shall be recorded.
(2) For Geotechnical Category 1, the supervision programme may be limited to inspection, simple quality controls and a qualitative assessment of the performance of the structure.
(3) For Geotechnical Category 2, measurements of ground properties or the behaviour of structures should often be required.
(4) For Geotechnical Category 3, additional measurements should be required during each significant stage of construction.
(5)P Records shall be maintained of the following, as appropriate:
- significant ground and ground-water features;
- sequence of works;
- quality of materials;
- deviations from design;
- as-built drawings;
- results of measurements and of their interpretation;
- observations of the environmental conditions;
- unforeseen events.
(6) Records of temporary works should also be kept. Interruptions to the works, and their condition on re-commencement, should be recorded.
(7)P The results of the inspection and control shall be made available to the designer before any changes are decided.
(8) In general, the design documents and records of what was constructed should be stored for 10 years, unless agreed otherwise. More important documents should be stored for the lifetime of the relevant structure.
4.2.3 Assessment of the design
(1)P The suitability of the construction procedures and the sequence of operations shall be reviewed in the light of the ground conditions, which are encountered; the predicted behaviour of the structure shall be compared with the observed performance. The design shall be assessed on the basis of the results of the inspection and supervision.
(2) The assessment of the design should include a careful review of the most unfavourable conditions, which occur during construction with regard to:
- ground conditions;
- ground-water conditions;
- actions on the structure;
- environmental impacts and changes including landslides and rockfalls.