Project location: Broxtowe Street, Nottinghamshire
Broxtowe Street was a Victorian end of terrace property, fairly typical of late Victorian housing stock up and down the country. In this case loss of fines within the soil, due to a leak from a culvert (underground water channel) was thought to be the cause of cracking in the superstructure and basement which was causing damp issues and evident signs of movement on the external skin of the building. The culvert had been re-lined by others prior to the commencement of the ReFORCE piling work.
Insurer’s/loss adjusters report
The loss adjuster’s report described the extent of the work to be carried out together with an explanation of the probable cause and whether or not settlement was progressive. Details were also provided on the construction of the building and whether there were any party wall issues. Details of the proximity and location of services were also provided: Avoidance of gas, water and electricity supplies into the house is a matter for health and safety and work could not proceed without understanding their routing.
Site Investigation report (SI)
GeoInnovations looked at the composition of the soil below the foundations. An examination of the soil profile provided us with enough information to say whether the ReFORCE system would work in this instance and trial pit data told us about the depth and design of the foundation. These crucial pieces of information allowed us to produce a design and estimate the length, size and depth of the piles which we proposed to form.
GeoInnovations produced a scheme showing the positions, depth and target diameter of each pile. The bearing capacity was also calculated. The exceptional diameter of the piles (500mm) and careful positioning avoid the risk of accentric support.
It is almost unheard of to provide a lump sum quotation for underpinning or piling or ground treatment work. Over 97% of the contracts carried out by STRESS UK come in at the quoted price.
ReFORCE piling: completion and warranty
Good written and photographic records are made of each job. In every case the amount of material used in each position, the driving logs, exact positions of piles, structural condition and cleanliness of the site are recorded. This information, together with the design proposal, calculations and application are sent to building control for their completion certificate. The ReFORCE piling 12 year warranty is applied for on completion of the contract.
N.B ReFORCE Piling is deemed to be a structural addition to the property and come under Building Control regulations. A sum is stated in the quotation to cover a building notice fee*. The design and the quotation are submitted in a single document. The design part is illustrative and serves to provide clear information for the installing technicians, clients engineer and building control officers.
*Not in Scotland.
Headroom was a maximum of 1.8 metres. The narrow access way into the basement was fully protected by sheeting. Equipment and materials were carried down to the working area by hand.
The positions of the ReFORCE permeation piles was marked out and access holes were then bored through the concrete floor and through the brick foundation corbel.
The ReFORCE lances were then driven to depth. To cope with the restricted headroom in the basement, shorter versions of the lances were coupled together to allow room for the driving tool.
The setting depth of the ReFORCE permeation piles was 2.73 metres below basement ground level (BBGL) where a layer of very strong ground was indicated in the Site Investigation.
Preparing the resin
Once set the ten ReFORCE lances were ready for the introduction of the GeoTek LV resin.
Injection of the product
Measured doses of the product were introduced into the ground under low pressure and at set levels.
Because the resin introduction process is relatively slow and works at low pressure, a small hand portable pump is sufficient for the purpose.