Foreword

This European Standard (EN 14731:2005) has been prepared by Technical Committee CEN/TC 288 "Execution of special geotechnical works", the secretariat of which is held by AFNOR.

This European Standard shall be given the status of a national standard, either by publication of an identical text or by endorsement, at the latest by March 2006, and conflicting national standards shall be withdrawn at the latest by March 2006.

According to the CEN/CENELEC Internal Regulations, the national standards organizations of the following countries are bound to implement this European Standard: Austria, Belgium, Cyprus, Czech Republic, Denmark, Estonia, Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Slovakia, Slovenia, Spain, Sweden, Switzerland and United Kingdom.

1 Scope

This European Standard is applicable to the planning, execution, testing and monitoring of ground treatment by deep vibration achieved by depth vibrators and compaction probes.

The following types of treatment are covered by this European Standard:

  • deep vibratory compaction to densify the existing ground;
  • vibrated stone columns to form a stiffened composite ground structure by the insertion of granular material which itself shall be densified. Generally, stone columns have a diameter greater than 0,6 m and lower than 1,2 m.

The following treatment methods are covered by this European Standard:

  • methods in which depth vibrators, containing oscillating weights which cause horizontal vibrations, are inserted into the ground;
  • methods in which compaction probes are inserted into the ground using a vibrator which remains at the ground surface and which in most cases oscillates in a vertical mode.

Treatment methods are outlined in Annexes A and B.

The following treatment methods, among others, are not included in this European Standard:

  • methods in which sand or stone columns are installed by means of impact or top vibratory driven casing:
  • methods in which very stiff columns are formed either by the addition of cement to granular material or by the use of concrete or any other binder;
  • dynamic compaction and other methods in which some form of treatment is applied to the ground surface;
  • explosive compaction.

2 Normative references

The following referenced documents are indispensable for the application of this European Standard. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies.

EN 791, Drill rigs - Safety

EN 996, Piling equipment- Safety requirements

EN 1990, Eurocode: Basis of structural design

EN 1997-1, Eurocode 7: Geotechnical design - Part 1: General rules

prEN 1997-2, Eurocode 7: Geotechnical design - Part 2: Ground investigation and testing

3 Terms and definitions

For the purposes of this European Standard, the following terms and definitions apply. Additional descriptions of some of the ground treatment methods are given in Annexes A and B.

3.1

deep vibratory compaction

type of ground treatment by deep vibration in which the main purpose is to densify the soil. The treatment is applicable to many granular soils and normally results in increased strength and stiffness, reduced permeability and reduced susceptibility to liquefaction

3.2

vibrated stone columns1)

type of ground treatment by deep vibration in which a depth vibrator is used to form continuous stone columns from the maximum depth of penetration up to the ground surface, and hence to form a stone column/soil structure which should have an increased strength and stiffness compared with the ground in an untreated state. The treatment is applicable to a wide range of soils and in granular soils some densification may also be achieved. Three installation processes, the dry top-feed process, the wet process and the dry bottom-feed process are described in Annex B

3.3

vibrating tool

item of equipment which is inserted into the ground to cause vibration at depth; commonly a depth vibrator containing oscillating weights or a compaction probe inserted into the ground using a top vibrator which remains at the ground surface

3.4

depth vibrator

basic component of ground treatment equipment used in the installation of vibrated stone columns and in vibro compaction, which vibrates horizontally by means of an eccentric weight rotating about its longitudinal axis, and penetrates into the ground. The penetration in the ground can be made easier by air or water flushing

3.5

top vibrator

vibrator which remains above the ground surface

3.6

compaction probe

tool for deep vibratory compaction which is inserted into the ground to transmit vibrations from a top vibrator which remains at the ground surface; wings, drainage or water flushing can be provided to facilitate the compaction process

3.7

deep vibro compaction

technique in which a depth vibrator is used to compact granular soil with or without the formation of stone

3.8

dry top-feed process

method of installing vibrated stone columns in which the hole formed by the depth vibrator remains open and specified granular material is fed directly into the top of the hole and compacted by the vibrator in stages (the process is described in Annex B)

3.9

wet process

method of installing vibrated stone columns in which flushing water removes soft material, stabilises the hole and allows specified granular material to reach the tip of the depth vibrator where it is compacted {the process is described in Annex B)

3.10

dry bottom-feed process

method of installing vibrated stone columns in which specified granular material is delivered directly to the tip of the vibrator via a feed pipe attached to the vibrator, with the vibrator remaining in the ground during the construction of the column to maintain the stability of the hole (the process is described in Annex B).

EN 14731:2005 Execution of special geotechnical works - Ground treatment by deep vibration