Vibratory ground improvement techniques


When using vibratory ground improvement techniques, the builder shall ensure that the engineer visits the site and provides competent supervision throughout the ground treatment process. Issues to be taken into account include:

  1. engineer checks
  2. location, depth and alignment of columns
  3. managing unforeseen circumstances.

Engineer checks

The engineer should provide competent site supervision throughout the ground treatment process and at critical stages, including:

  • the inspection of setting out
  • the installation of columns during the early stage of the work
  • checking of materials
  • where installation data differs from design assumptions
  • where changes in treatment layout are required.

Some aspects of sitework may be the responsibility of the engineer or their representative, or of the specialist contractor, rather than of the builder.

Location, depth and alignment of columns

Supervision should ensure that:

  • the minimum required depth of the stone columns is achieved and each one correctly located (the builder should provide sufficient profiles to enable locations to be checked)
  • the stone columns are located either centrally under the foundations they are to support or are in the predetermined staggered arrangement, at a maximum of 2m centres and at the intersection of adjacent reinforced concrete strips
  • missing stone columns are replaced
  • stone columns which are misaligned by more than 150mm in any direction are replaced
  • the location of all stone columns is checked by the engineer’s representative prior to the specialist plant leaving the site.

Managing unforeseen circumstances

Table 3: Actions for managing unforeseen circumstances

Allowance should be made for unforeseen obstructions that require either local removal and backfilling prior to treatment, realignment or additional columns, coupled with local amendment of foundation design.