9 Supervision, Testing and Monitoring
9.1.1 A schedule for the supervision should be available at the construction site. In this schedule as a minimum the following shall be noted :
- frequency of the different checks;
- critical values of the deformations, forces and water levels.
9.1.3 Supervision shall also include, if applicable, the following checks and observations :
- are site conditions, soils, groundwater and free water in accordance with the data of the design;
- are there any obstructions in the ground which hinder the sheet pile driving and which were unforeseen at the design stage;
- is the driving method capable of installing the sheet piles in accordance with the design and environmental requirements;
- does the sequence and method of execution comply with the execution scheme and are the criteria regarding the progression from one stage to the next as stated in the scheme (see 7.4);
- are the primary and secondary elements for a combined wall properly stored and handled;
- do the sheet piles, primary and secondary elements and all other structural elements for a combined wall fulfil the requirements referred to in clause 6;
- are treatments, materials and products used for protection of the steel elements and the preservation of wooden parts, in accordance with 6.4;
- are templates and other devices for guiding the piles during driving, well positioned and sufficiently stable to ensure that the piles will meet the tolerances specified in 8.6;
- is the verticality during positioning and driving of the primary elements of a combined wall checked with sufficiently accurate instruments;
- are sheet piles, primary and secondary elements for a combined wall within the tolerances specified in 8.6;
- are the positions of the elements of the anchorages in accordance with the design;
- are the surcharges behind the sheet pile wall within the calculated limits at all stages of the execution;
- is there any damage to nearby buildings, installations or underground services which could be attributed to the execution works;
- during the execution works, have any events occurred which have an adverse effect on the quality of the structure ?
9.3.1 The rate of penetration of at least some of the piles should be recorded in order to establish whether the soil conditions comply with those assumed in the design.
9.3.2 Where piles are designed to carry vertical loads, the rate of penetration shall be recorded over at least the last metre of driving, unless the sheet piles are placed in or on bedrock. In that case, in order to establish that the sheet piles have reached the required depth, monitoring shall be carried out in accordance with the requirements of the design.
9.3.3 If groundwater and free water levels are critical parameters according to the design, they shall be monitored at time intervals which are short enough to obtain a reliable pattern of these levels.
9.3.4 It is recommended that the monitoring of the groundwater levels or pore pressures are continued after the completion of the works until it is established that no adverse effects will occur.
9.3.5 Where the project is situated in a built-up area, the vibration and noise levels at the construction site and at the most exposed buildings should be recorded periodically. Such measurements should be done in accordance with local practice in order to compare the results with criteria which are appropriate for the area.
9.3.6 The horizontal displacements of the top of the sheet pile wall should be periodically measured with appropriate accuracy at predefined points in such a way that the results can be compared with the expected design values.
9.3.7 Where sensitive buildings or installations are close to the sheet-pile wall structure, in addition to the measures described in 9.3.6, at least the following should be considered :
- displacement measurements at selected depth;
- settlement measurements of these buildings and installations;
- anchor force measurements.
9.3.8 When driving a combined wall, de-clutching detectors should be applied to at least some of the secondary elements. This should be done in combination with recording the rate of penetration over the full depth such that the driving diagram can be used as a control to check possible de-clutching.
NOTE Monitoring the rate of penetration of the sheet piles under difficult circumstances often gives only an approximate indication regarding possible de-clutching. De-clutching detectors can be useful to verify the integrity of the sheet pile wall after completion.
9.3.9 During the extraction of sheet piles or primary elements, the extraction time should be recorded for each pile or element. For some of them the ground displacements should be measured.