4.5 Vibratory ground improvement techniques

Also see:

2.14.14.2

4.5.3 Desk study and site investigation

The engineer shall ensure a desk study and site investigation are undertaken and findings used to inform the design.

The engineer should establish the scope of, and supervise, the site investigation, taking account of the findings of the desk study, and relevant standards listed in Clause 4.5.1.

The specialist contractor should be satisfied that the site investigation provides adequate and representative information in order to design the ground improvements. The results of the site investigation and desk study should be sent to NHBC prior to work starting and should, as a minimum, determine the items listed in Table 1.

Table 1: Results of the site investigation and desk study

Item to be determinedGuidance
Depths and properties of natural materials under the siteIncludes the presence of caves, workings, or natural phenomena such as rocks or soils which dissolve or erode when exposed to the passage of water
Data for comparison with post-treatment properties should be established
Extent and nature of any areas of filled ground on the siteIncludes:
• proportions and distribution of constituent materials
• state of compaction of the fill material throughout its depth
• grading and particle size distribution of fill materials
• potential for gas generation from fill materials
• potential for spontaneous combustion of fill and/or natural deposits
Presence and extent of any existing or redundant services and drainsIncludes information on the extent and nature of the backfill to the excavations
The effect of sustainable drainage systemsIncludes the effect that any sustainable drainage system (SuDS) may have on the geotechnical parameters of the site
Presence, level and nature of any ground waterIncludes the potential for ground water to rise and cause heave or collapse by saturation
Previous structuresIncludes any potential underground obstructions or hard-spots, eg basement walls, floor slabs, which remain
Occurrence of contaminated substancesIncludes the presence and extent of contaminated substances or gases present or suspected

Last updated: 2nd January 2024

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