BRE BR513 PDF

Purpose and objectives

The purpose of this report is to give guidance and advice for on-site treatment of existing natural and reworked natural soils, using lime, cement, ggbs and coal fly ash as appropriate, for application on residential developments.

The objectives of treatment are:

• to enable the soil to be handled and placed such that maximum compaction with minimal air voids is achieved

• to achieve a volumetrically stable treated soil

• to realise a development that is free from detrimental settlement.

The technical suitability of hydraulically treated soils for domestic building applications is addressed in detail, with guidance on:

• construction

• the potential of the technology

• any limitations that should be considered in particular circumstances.

A review of the available treating agents, site investigation techniques specific to the technology and necessary soil chemical analysis appropriate to ground treatment is included, together with verification testing requirements, including, for example:

• laboratory evaluation tests

• corresponding site control tests during construction

• site performance tests after construction.

Verification testing is recommended to ensure that the treatment is competent, stable and durable for the design life of the development.

As with all construction techniques, the use of competent, experienced personnel who understand the processes and potential problems is essential to successful soil treatment. Every job is unique and needs to be assessed on its own merits. There is no blanket recipe to cover all situations.

For soil treatment under housing, it is important to note the following:

• It will form just part of the overall foundation to the development as it will have to perform in combination with the underlying/adjacent untreated ground and the overlying substructure for the development.

• It may also need to integrate with other ground engineering issues such as contamination, aquifers, water dispersal and/ or attenuation.

For these reasons, it is recommended that a single, suitably qualified, adequately insured professional party be contracted to offer ‘a duty of care’ overview of the works. The appointed party should be capable of: • specifying the correct site investigation at the outset to ensure that soil treatment is an appropriate solution

• designing and monitoring the soil treatment, taking account of the advice given in this report

• understanding and controlling the effectiveness of the completed engineered groundworks, including the treated soil and its integration with other ground engineering activities and issues on the site

• understanding the overall performance of the treatment and the underlying untreated soils.

Finally, it should be noted that the construction equipment used for soil treatment consists of many pieces of plant, each of quite significant size. Thus the recommendations that follow assume that the use of soil treatment will normally be limited to large housing developments where soil management can be carried out effectively and the construction equipment has the room to be used efficiently. Therefore, reference to ‘plot’ or ‘footprint’ in the following sections relates to the ground underneath a group of houses rather than an individual dwelling. It is difficult to make comment here on what constitutes a viable plot/ footprint size as this will be site-specific. The best advice can only be determined following discussions between developer and contractor.