9.4 Monitoring during construction

9.4.1 The type, extent and accuracy of monitoring and testing requirements shall be in accordance with Clause 4 of EN 1997-1:2004.

NOTE Where the observational method is used particular attention needs to be made to 2.7 of EN 1997-1:2004.

9.4.2 The details of monitoring records to be made both during and after execution of the works are specified in Clause 10.

9.4.3 Monitoring the horizontal and vertical movement of the works should be performed.

NOTE An appropriate monitoring program can vary (from visual inspection to full instrumentation) depending on Geotechnical Category or project specification.

9.4.4 If movements approach or exceed threshold values, then stabilisation measures, defined in the design, shall be implemented and the construction procedures reviewed.

NOTE Changes to construction procedures that may permit construction to continue include reducing bench depths and lengths, time to install facing and groundwater control.

9.4.5 Visual inspection of excavated ground for signs of ground water shall be carried out. Where encountered, the adequacy of the drainage system for the observed water level shall be confirmed.

9.4.6 If the design is sensitive to changes in ground water, then piezometers should be installed and monitoring undertaken.

9.5 Measures to facilitate long-term monitoring

9.5.1 The need for long-term monitoring should be assessed on the Geotechnical Category of the structure.

9.5.2 If long-term monitoring is deemed necessary, then the purposes, provisions to be made, instrumentation required and monitoring frequency shall be clearly specified. Where appropriate limit values and actions are to be taken shall also be clearly specified.

9.5.3 Long-term monitoring of the soil nail construction may include, but is not limited to:

  • a) movement of the works or adjacent structures and slopes;
  • b) load-tests to sacrificial nails or production nails;
  • c) efficiency of drainage systems;
  • d) changes in groundwater and hydro-geology;
  • e) degradation of soil nails and facing systems;
  • f) forces in soil nails;
  • g) suggestions for long-term monitoring are found in A.6.

9.5.4 When considering long-term monitoring, the safety of personnel shall be considered and safe access provided.

9.5.5 If the design of the soil nail works incorporates the observational method, then the monitoring requirements of 9.4 and 9.5 shall be considered.

10 Records

10.1 Records of construction shall be made in accordance with Clause 4 of EN 1997-1:2004.

10.2 A construction and nail installation plan shall be prepared and shall be available on site containing the technical specification related to the nail system to be used.

10.3 A nail installation plan shall contain at least the following information:

  • a) nail type with designation;
  • b) number of nails;
  • c) location, orientation and inclination of each nail and tolerances in position, to an agreed datum;
  • d) required load carrying capacity of the nail;
  • e) installation technique;
  • f) known obstructions and any other constraints on nail activities;
  • g) method of corrosion protection;
  • h) nail testing undertaken;
  • i) schedule of work.

10.4 An execution record shall be kept. This record shall include any special features of construction.

10.5 The following information as appropriate should be included in the execution record for each nail installation:

  • a) project/element;
  • b) nail designation;
  • c) installation date;
  • d) nail type, diameter, length, orientation;
  • e) installation method;
  • f) drilling method;
  • g) bore hole cased/not cased and borehole diameter;
  • h) flush method;
  • i) underground conditions (short description);
  • j) hydro-geologic conditions;
  • k) grout consumption;
  • l) remarks (climate, weather and temperature);
  • m) special measures;
  • n) test results (if performed) and actions taken (if any).

10.6 As-built plans shall be compiled after completion of the nails and kept with the construction records. Any acceptance certificates issued by regulatory authorities for materials used in the nail installation shall be held with the construction records.

11 Special requirements

11.1 General

When executing soil nailing works, the relevant national standards, specifications or statutory requirements shall be observed regarding:

  • a) security of the site;
  • b) safety of the working procedures;
  • c) operational safety of plant and auxiliary plant, equipment and tools.

11.2 Noise

11.2.1 Precautions shall be taken to ensure that operators are not exposed to noise levels that exceed the limits prescribed in international or national regulations.

11.2.2 Measures shall be taken not to cause danger or unreasonable nuisance to those living, working or passing nearby the works.

11.2.3 Measures should be taken to minimise the noise at source and/or shield it from the general public.

11.2.4 It can be necessary to erect warning signs where it is likely that motorists or others could be subject to danger by an unexpected noise.

11.3 Environmental damage

Appropriate measures shall be taken in order to limit or avoid adverse effects on the environment. The following environmental impact risks shall be considered:

  • a) excessive induced movement in the construction itself or in adjacent ground or structures;
  • b) pollution of groundwater or surface water;
  • c) unacceptable changes in the natural groundwater flow;
  • d) air pollution;
  • e) tree falling and damage;
  • f) visual impact of completed works.

EN 14490:2010 Execution of special geotechnical works – Soil nailing