NHBC Standards 2006

4.6 Vibratory ground improvement techniques


4.6 - M1Materials standard
4.6 - M2Stone fill
4.6 - M3Granular material

4.6 - M1
All materials shall:
(a) meet the Technical Requirements
(b) take account of the design

Materials that comply with the design and the guidance below will be acceptable for use in conjunction with vibratory ground improvement techniques.

Materials for use in conjunction with vibratory ground improvement techniques shall comply with all relevant standards, including those listed below. Where no standard exists, Technical Requirement R3 applies (see Chapter 1.1 'Introduction to the Standards and Technical Requirements').

References to British Standards and Codes of Practice include those made under the Construction Products Directive (89/106/EEC) and, in particular, appropriate European Technical Specifications approved by a European Committee for Standardisation (CEN).


4.6 - M2
Stone fill for forming columns shall be compatible with the ground conditions, and be suitable for the vibratory ground improvement process

Stone fill should be clean, hard, inert material complying with the guidance given in Appendix 4.6-B.

In acidic ground conditions, limestone fill may not be acceptable.

Natural gravel or crushed rock aggregate of nominal single-size within the range 20-75mm will normally be acceptable.


4.6 - M3
Granular material for raising site levels before treatment or adding during deep compaction shall:
(a) be free from hazardous materials unless appropriate precautions are taken, and
(b) be suitable for compaction

The appropriate precautions to be taken where hazardous materials are present in fill are detailed in Appendix 4.6-B.

The test requirements for fill given in Appendix 4.6-B should be followed where appropriate.

Well graded, inert fill which passes a 100mm x 100mm screen in all directions and contains less than 10% fine material of silt or clay size will normally be acceptable for raising site levels.

The grading of material for adding during deep compaction should be within Zone A of the chart shown in Design clause D7 and Appendix 4.6-A.