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 determined | Guidance |
|---|---|
| Depths and properties of natural materials under the site | Includes 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 site | Includes: • 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 drains | Includes information on the extent and nature of the backfill to the excavations |
| The effect of sustainable drainage systems | Includes the effect that any sustainable drainage system (SuDS) may have on the geotechnical parameters of the site |
| Presence, level and nature of any ground water | Includes the potential for ground water to rise and cause heave or collapse by saturation |
| Previous structures | Includes any potential underground obstructions or hard-spots, eg basement walls, floor slabs, which remain |
| Occurrence of contaminated substances | Includes the presence and extent of contaminated substances or gases present or suspected |
Last updated: 2nd January 2024