4 Information needed for the execution of the work

4.1 Prior to the execution of the work, all necessary information shall be available.

4.2 This information shall include:

  • a) relevant information regarding the site conditions;
  • b) the location of main grid lines for setting out;
  • c) drawings with the location and length of the drains;
  • d) any legal or statutory restrictions;
  • e) method statement for the vertical drain installation (see 8.1);
  • f) characteristics of the drains (physical and hydraulic characteristics), accompanying document for CE-marking;
  • g) specification for the drains and other materials to be used (see Clause 6) and the schedule of any testing and acceptance procedures for materials incorporated in the works;
  • h) description of a suitable quality management system, including supervision and monitoring.

4.3 The information regarding the site conditions shall cover, where relevant:

  • a) the geometry of the site (boundary conditions, topography, access, slopes, headroom restrictions etc.);
  • b) the ground properties of the site which may influence the execution of the vertical drains:
    • soil description (soil type, soil stratification and existence and frequency of sand and silt layers, hard layers);
    • penetration resistance (e.g. results of penetration tests);
    • composition, lateral extent, thickness and firmness of the surface stratum, tree roots, fill etc.;
    • presence of cobbles or boulders or cemented layers that can cause difficulties for the execution or can require special installation equipment;
  • c) the following climatic and environmental information:
    • weather information in areas with extreme climatic conditions;
    • marine conditions (currents, tidal movements, wave heights etc.);
    • environmental hazards (any water and subsoil contamination, which could affect the execution method, the safety of the work or the discharge of excavation material from the site shall be documented, including the presence of hazardous gas and occurrence of unexploded ammunition);
  • d) the existing underground structures, services, known contamination and archaeological constraints;
  • e) the environmental restrictions, including noise, vibration and pollution;
  • f) planned or ongoing construction activities, such as dewatering, tunnelling and deep excavations;
  • g) previous experience from drain installation work adjacent to the site;
  • h) the characteristics of the working platform and the drainage layer (physical and hydraulic properties);
  • i) the conditions of structures, roads, services etc. adjacent to the work.

4.4 For the loading operation the following information shall be available:

  • a) construction programme for loading;
  • b) preloading (temporary and permanent loading);
  • c) time schedule for loading and possible preloading;
  • d) unit weight of fill used for preloading;
  • e) notice of any restrictions such as construction phasing required in the design;
  • f) monitoring programme.

4.5 The following instructions shall also be given:

  • a) reporting procedure for unforeseen circumstances, or conditions revealed that appear to be different from those assumed in the design;
  • b) reporting procedure, if an observational method of design is adopted.

4.6 Any additional or deviating requirements falling within the permission clauses given in this European Standard shall be established and agreed upon before the commencement of the works.

5 Geotechnical investigations

5.1 General

5.1.1 The geotechnical investigations carried out for the design of vertical drainage work following the requirements of EN 1997 shall provide information for the installation of the vertical drains, see 4.3 b).

5.1.2 The geotechnical investigation report shall be available in sufficient time to allow for planning and execution of the vertical drainage works.

5.1.3 If the geotechnical investigations carried out are deemed insufficient, a supplementary investigation should be conducted.

5.2 Specific requirements

5.2.1 Apart from the general geological description and the details listed in EN 1997-1, the site investigation report shall contain information regarding ground conditions for the execution of vertical drain installations and for loading, see Annex A and Annex B.

5.2.2 Information about ground conditions shall comprise:

  • a) piezometric levels of groundwater, its variation and possible deviation from hydrostatic pressure conditions;
  • b) undrained shear strength.

5.2.3 The ground level and location at any point of investigation or testing should be established relative to the recognised national datum or to a fixed reference point.

EN 15237:2007 Execution of special geotechnical works — Vertical drainage