9 Supervision, monitoring and testing
9.1.1 A suitably qualified and experienced person shall be in charge of the work.
9.1.2 The person in charge shall be responsible for:
- the conformity of the work with this standard and with any additional specification and agreed working procedure;
- the monitoring of pile construction and keeping of all necessary records; and to
- keep the clients representative and/or designer informed of any variations or deviations from the expected situation or condition of the site or any cases of non conformity.
9.2 Monitoring of pile construction
9.2.1 The monitoring of all works connected with the execution of the various stages of construction of a displacement pile shall be in accordance with the method statement and piling plan made up in accordance with the design and ENV 1997-1.
9.2.2 The pile construction process shall be monitored including previously installed piles and all relevant data indicated in 10.3 and when required those indicated in 10.4 shall be recorded.
9.2.3 The effects of piling close to sensitive buildings or potentially unstable slopes should be monitored. Methods include vibration, pore pressure, deformation and inclination measurement. The measurement should be compared to criteria for acceptable performance.
9.2.4 Frequency of monitoring shall be specified and agreed before commencement of piling work.
9.2.5 Records of monitoring shall be provided within an agreed period and kept on site until the completion of the piling works.
9.2.6 All instruments that are used for monitoring the pile installation and/or the effects of installation shall be suitable for the purpose and calibrated.
9.2.7 All non conformance shall be notified.
9.2.8 The full driving record of a proportion of the piles should be recorded in order to establish whether the soil conditions correlate with those used in the design.
This should also include:
- for impact hammers the hammer drop height and weight or hammer energy together with number of blows per unit of penetration;
- for screw piles the torque and pressure applied;
- for vibrated piles the power rating, amplitude and frequency and rate of penetration;
- for jacked piles force applied to the pile.
9.2.9 Where driven bearing piles are driven to a final set, energy and set shall be measured.
9.2.10 Where heave or lateral displacements are likely to be detrimental to pile integrity and performance, pile top level and plan location readings with respect to a stable reference level mark should be taken before and after driving of neighbouring piles and/or after possible excavations.
9.2.11 Prefabricated piles, which have risen more than the acceptable limits, shall be driven back to their original design criteria.
NOTE For piles, when it is not possible to redrive the pile, a load test to determine its load and settlement characteristics would allow the overall performance of the pile group to be established.
9.3.1 The testing of piles shall be in accordance with relevant ENV 1997-1 or with the specifications in the design.
9.3.2 Pile tests can be used for:
- assessment of design parameters;
- verification of pile design;
- proof of resistance – deformation characteristics in the general range of specified actions;
- compliance with the specification;
- proof of the integrity of a pile.
9.3.3 Pile tests may consist of:
- static pile load tests:
- maintained load pile test;
- constant rate of penetration pile test;
- dynamic pile load tests (high strain);
- integrity tests:
- sonic test, dynamic integrity test (low strain);
- sonic coring;
- dynamic integrity test (high strain);
- control tests:
- concrete core drilling for obtaining material samples;
- inclinometer test to check the verticality, inclination, bending of a pile from a pre-placed tube system.
9.3.4 Where static load tests are used the design and installation of the various reaction items shall be in accordance with relevant codes and method statements.
9.3.5 Static and dynamic load testing of piles should be carried out after sufficient time, taking account of any gain in strength of the pile material, and with regard to changes in soil resistance due to pore pressure effects.
9.3.6 Dynamic and integrity tests shall be carried out using equipment built and approved for the purpose. These tests are required to be interpreted by persons competent in this area, who shall also have a knowledge of the techniques of piling and experience of the specific ground conditions.
9.3.7 The records of any testing shall provide:
- the testing method and procedure;
- the test result;
- the conclusions on the pile test.